Thanx for the pointer to an excellent paper. I have heard about Niagra Falls eroding many feet in a single day, long ago. Is it possible that glaciers can enlarge their exits to the ocean through erosion ?
I am wondering where I might find best estimates for how much a shifting pole-to-equator precipitation gradient would offset sea level rise from thermal expansion and glacier loss over the 21st century? Obviously we’re already including net growth in the interior of ice sheets, but I can’t imagine that the ratio of melt to growth remains constant with time.
We lay-folk cannot access the full text, but firstly how do the predictions take into account BAU and more importantly sensible recognition of BAL – Business as LIKELY?
We are not going to get the inertia of combined Asia, India, Europe, UK, USA, Arabia, Africa and Australia to stop commissioning a 500MW coal fired power plant every three days for the foreseeable future. Unless a realistic BAL is recognised in the expected forcing then a modest 0.8m doesn’t tell us much.
Secondly; Does the paper unambiguously declare the longer term outcome? Many people assume when scientists say that the sea is going to rise 0.8m by 2100 that that is the end of the matter, but of course its not. Unless we get CO2 back below 275ppm the ice is going to continue to melt and we are going to get +80 metres of rise, and most of the good infrastructure works in coastal cities around the world are merely serving to enhance the dive experience for future tour-boat operators.
[Response: 80 meters is all ice gone, including East Antarctica - which would take us back to the Eocene. I think we can rule that out for the time being! - gavin]
How much will sea levels rise? From my reading and guesstimates,
I would say 70 feet by the year 2500 A.D….but that is still a long way away,
so no need to panic. Then again, it could happen much quicker if things go haywire in a way that we cannot predict now. I would be worried, very worried. Most people in the world just
want to keep driving their cars to work, though, and go on living as if there
is no tomorrow. You know what? Maybe there will be no tomorrow, if we keep this up. But give it another 500 years. No need to panic now. Ask Jimmy Lovelock.
.. well nothing to panic about until you start thinking about what is involved shifting half the worlds population, food production and industrial base up above the 80 metre line, at the same time as our primary energy source (oil) needed to accomplish this is past peak and never to be seen again. No worries! Yeah rite!
[Response: 80 centimeters (not 80 meters), though that is already large enough! - gavin]
For those of you who do not read Dutch: The Deltacommissie gives indeed 55-110 cm SLR for 2100 global, and the bit more for Holland (executive summary, p. 10, 2nd paragraph) is 0.65-1.30 m relative sea level rise (expected in Holland) by 2100, 2-4m by 2200.
From the draft of an article: ” Saying “Americans will never give up keeping their houses too cold in the summertime” sounds silly next to “Lots of children and older people will get sick and some will die if we don’t stop Global Warming.” ”
Thanks to RealClimate for helping the rest of us understand climate, but doesn’t it make sense to be “alarmist” when alarming things keep happening “ahead of schedule?” Things icy are a good example, from arctic icecap extent to Greenland and Antarctic glacier dynamics.
I think it is time to say that you have to be a bit alarmist to be a real conservative… as in, preserve the good that we’ve got, before it is too late.
Or maybe I’m just cranky because I can’t go home to New Orleans for a few more days.
One meter of sea level rise by 2100 would be catastrophic from my perspective on the upper Texas and Louisiana coasts. These areas provide the world with an “experiment” in sea level rise and what it means in terms of real world impacts. Subsidence from ground water withdrawal and oil and gas extraction have caused regional subsidence along these coasts ranging from 1′ to 15′. The USGS has a great publication discussing ground water extraction and subsidence. Robert Morton and others have documented the oil and gas induced subsidence and its affect on coastal wetlands and beaches in the Journal of Coastal Research and other publications. The Conrad Blucher Institute (on line) has developed apparent sea level rise rates for the Texas and SW Louisiana coasts (this accounts for both subsidence and eustatic sea level changes). Much of the area is already experiencing rise rates on the order of a meter or more per century due to the ongoing production of oil, gas and associated water causing collapse and consolidation of the producing rock strata.
The bottom line from this experiment is that simply drawing a new coastline along a topographic contour is overly simplistic and greatly underestimates the damage to human infrastructure and the loss of coastal environments. Just look at the issue of wetland loss and increased storm damage or fishery losses in SW Louisiana. Thousands of acres of rice fields have been abandoned because they no longer have the needed elevation and slope to drain. Beaches and dunes are lost entirely. Wildlife refuges and Parks and being eroded away and converted to open water. Cities once protected by tens of miles of wetlands are now near open water and are subject to hurricane storm surge damage. The NW Gulf of Mexico coast is in crisis and this is before eustatic rise really kicks in.
The overall effect from the ancillary coastal changes is to take the damage estimates and number of people affected by a future sea level rise scenario and multiply it by ten.
I was led through a reference from the paper by Pfeffer et al. to Rignot et al., Nat. Geosci.,v1, p106, specifically Fig.1, which shows mass imbalances across Antarctica. I note that the large imbalances in Pine Island and Thwaites glacier lead directly to the Byrd subpolar basin, and the small mass loss in Tottenham points to a similar, but shallower basin, as may be seen from http://upload.wikimedia.org/wikipedia/commons/b/b7/AntarcticBedrock.jpg
A point of interest in Pfeffer et al., p1342
“The aggregate cross sectional gate area of PIG and Thwaites is ca. 120Km^2″
and refers to a private communication by Rignot. However I note that Rignot, in Phil. Trans. Roy. Soc. A, 2006, v364, pp1637-1655, notes that Thwaites is widenning and may double in width. As these (PIG,THW,TOT) glaciers retreat toward deeper basins inland, is it not the case that they would all widen?
If so, would not the gate area increase ?
Odd — the words “… Previous projections of 20 feet or more of sea level rise by the end of the century …” appear twice — attributed both to a phone call with the author by the science news writer, and in direct quotes in the official press release. Is there anything like that claim in the published paper? Else this is odd spin.
In my opinion it is clearly the press release from the University of Colorado that is either immensely stupid or deliberately misleading, aimed at defusing the study’s results. It starts like this:
Global Sea-Rise Levels By 2100 May Be Lower Than Some Predict, Says New CU-Boulder Study
September 4, 2008
While the disintegrating Columbia Glacier in Alaska is adding to ocean levels this century, the total global sea rise by 2100 may be lower than some are anticipating, according to a new University of Colorado at Boulder study. Photo by Tad Pfeffer/University of Colorado
Despite projections by some scientists of global seas rising by 20 feet or more by the end of this century as a result of warming, a new University of Colorado at Boulder study concludes that global sea rise of much more than 6 feet is a near physical impossibility.
Under BAU forcing in the 21st century, the sea level rise surely will be dominated by a third term: (3) ice sheet disintegration. This third term was small until the past few years, but it is has at least doubled in the past decade and is now close to 1 mm/year, based on the gravity satellite measurements discussed above. As a quantitative example, let us say that the ice sheet contribution is 1 cm for the decade 2005–15 and that it doubles each decade until the West Antarctic ice sheet is largely depleted. That time constant yields a sea level rise of the order of 5 m this century. Of course I cannot prove that my choice of a ten-year doubling time for nonlinear response is accurate, but I am confident that it provides a far better estimate than a linear response for the ice sheet component of sea level rise under BAU forcing.
Hansen, J. (2007) Scientific reticence and sea level rise Environmental Research Letters2 p.4
[Response: That's just a thought experiment for contrast to a linear response, not an informed projection. The quote from later on in that paper is cited above where he gives his expectation. - gavin]
In Holland (at least the western part of it), most of the terrain is a mix of sand and peat bog. Since those lands have been transformed into polders, they have slowly been going down. The reason is that the peat bog dries and shrinks. This worsens our situation, and I fear Holland will finally lose to the battle with sea somewhere in the coming centuries. Long before that, silt creeping into the land and the growing risk of floods are going to be huge problems.
However, the situation in Bangladesh is much worse, the poor people there cannot afford a multi-billion delta plan like Holland.
Comment by Vincent van der Goes — 5 Sep 2008 @ 2:28 AM
Just now, it is raining in Greenland. Rain advects heat into the ice, even into the lower layers of ice that support huge weights of ice. As ice warms, it weakens. Warmed foundation ice is not strong enough to support the ice above it. At some point the foundation begins to collapse and the result is a ice/water debris flow with very high initial acceleration. The proper model is the Missoula floods. Such floods are only constrained by the volumes of water and ice in the system. Such water and ice floods can carve any outlets that they need. Look at the potholes in Washington State. Big holes carved into basalt by water flowing over it. The basalt was not even blocking the flow, and the water still carved big holes into it.
There is a lot of ice in the Greenland system that only needs a lot of water to flush it into the ocean. With a warm North Atlantic and a seasonably open Arctic Ocean, the amount of rain on Greenland could be considerable even by British Columbian standards. Greenland could collect more water than the old Clark River watershed, and thereby move more ice to the ocean.
Then, this article only addresses sea level rise from Greenland. If it is warm enough for Greenland to melt a bit, it is likely also warm enough for Antarctica to melt a similar amount. And, it is likely that permafrost will melt. That give us another meter of sea level rise, for a total of 5 meters of sea level rise. What would 5 meters of sea level rise do to the stability of the WAIS? Would that unpin any of it and set it sliding into the water?
My best guess based on guesses about heat transfer by rain in Greenland is that we will see 3 meters of sea level rise in the next 30 years, and another 3 meters in the following decade, for a total of 6 meters in 40 years. Of course that is outrageous. However, 30 years ago, I would have said that there was not even a 1 in a million chance that it would be raining in Greenland on 9/4/2008. In the context of an ice-only system in Greenland, my estimate is silly. However, with open water on both sides resulting in large transfers of latent heat, I think the possibility of water/ice slurries must be considered.
Before you jump up and tell me I am crazy, get out your science stuff; and go defrost a few freezers, making careful observations of the ice and melt water. Does it melt or does it fall out in chunks? What happens when a glacier gets to the ocean? It calves. The point is, ice near its melting point tends to fracture – suddenly – leaving two chunks of ice separated by a film of water. Such ice/water slurries tend to move downhill easily. For example, pieces of ice from the freezer tend to bounce out of the freezer onto the floor. How far does it fall, and how far from the freezer does it end up? And, In the case of Greenland, after it has been rained on for 20 years, we are talking about a lot of ice near its melting point.
Who would like to step forth and tell me why it is likely to stop raining in Greenland?
[Response: Rain on the flanks is not that uncommon, but enough rain on the bulk of the ice sheet to affect the surface mass balance as much as you suggest is not on. The ice sheet is 3km high, which given the lapse rate is ~30 C below the temperature at sea level - it simply can't support large amounts of liquid water. As I mistakenly said to Mike below, going beyond the science is not helpful. - gavin]
As far as human adaptation is concerned, it seems to me that a steady sea level rise of say one metre per century for five centuries would be more difficult to cope with than a one off rise of five metres in one century.
At least in the latter case humanity would have some line in the sand above which to start trying to rebuild coastal cities and ports. A constantly shifting sea level, in whichever direction would be very difficult to cope with.
I think it’s fair to say that in the paper you quote Hansen has gone a bit further than you suggest:
‘Under BAU forcing in the 21st century, the sea level rise surely will be dominated by a third term: (3) ice sheet disintegration. This third term was small until the past few years, but it is has at least doubled in the past decade and is now close to 1 mm/year, based on the gravity satellite measurements discussed above. As a quantitative example, let us say that the ice sheet contribution is 1 cm for the decade 2005–15 and that it doubles each decade until the West Antarctic ice sheet is largely depleted. That time constant yields a sea level rise of the order of 5 m this century. Of course I cannot prove that my choice of a ten-year doubling time for nonlinear response is accurate, but I am confident that it provides a far better estimate than a linear response for the ice sheet component of sea level rise under BAU forcing.’
I say only a bit further because his estimate is obviously tentative, but the upper estimate of Pffer et al is less than half Hansen’s ballpark figure.
What about the Nature report that it is not a practical situation to have more than 2m rise by 2100. Can you please read the paper and give us a report (us layfolk cannot access it anyway).
In any case, I agree with Andrew at 10. The impacts will be huge. For example, large areas of many of the highest producing regions are within a couple of metres of sea level. Ganges delta, Nile delta, Southern Vietnam, areas around the China Sea, Florida, Netherlands, etc. look at http://flood.firetree.net/ and you can see what I mean.
Our grandchildren may not know what it is like to walk on a sandy beach.
Gavin no, I do mean 80 metres. 80 metres is when its all gone, isn’t it. What magik event can occur in a post oil post BAL post 400ppm CO2 world to stop continuous melt from today thru 30cm thru 80cm thru 2m to all-gone-80 metres? Anything you can think of?
If none of the Realclimate guru’s want to correct Aaron Lewis’s errors (#17) maybe they had better start thinking greater sea level rise. My unscientific freezer melting sure sounds like his experience. Don’t get me wrong, a 1 meter (default plus a little more) rise by 2100 is bad enough but 3-5 meters by 2050 is catastrophic by anyone’s judgement.
Where does Slioch (#18) think the human race will get the energy and material resources to rebuild the world’s ports? After a five meter SLR in one century mankind will be struggling to feed itself until the population adjusts significantly. Can we even consider what that stuggle will be like? It’s not likely to be pretty, that much we do know.
Finally, will someone answer Nigel Williams (#22). What will stop the melting? That there may be few if any human observers by that time (80 meters) does not render it an uninteresting question.
All of these questions stem from only one. When will the human race recognize it is rendering the planet uninhabitable with its addiction to fossil fuel? When will people stop turning the key and flipping the switch?
[Response: But where are you getting the idea that sea level will rise 3 to 5 m by 2050? No-one serious has ever predicted that. The problems that exist with the projections grounded in some physics are serious enough without having to male up even scarier monsters. You might think it helps 'up the ante', but it doesn't - it just allows people who don't want to think that there is any problem the opportunity to paint all statements as alarmist nonsense. If you decry the abuse of science by the disinformation campaigns, you should try harder to follow the science (uncertainties and all) on these issues as well. - gavin]
[Updated response: Sorry! I missed the comment above (#17) that you were referring to. So transfer all of the above response to #17. - gavin]
Ricki, above, no. 51 post, re: “Our grandchildren may not know what it is like to walk
on a sandy beach.”
Powerful thought, Ricki. But I think it will most likely be our grandchildren’s descendants in far distance future who will have that experience, maybe 30 generations hence. We are okay for the next 200 years, I think. But the problems that will come later are arising (no pun intended) now, and we need to tackle them now, if indeed they can be tackled. I think your projection is too, soon, but it is poetic one. And this discussion sometimes need poetry, too. Science and poetry combined. Thanks for that.
Our greatgreat X 30 grandchildren might also know what it is to live in a Lovelock Retreat. A what, you asked? Google it and see.
In a minor but related question not really suited for the moderators of this blog, has anyone considered the economic affect of the growing belief of significant sea level rise among real estate buyers worldwide?
Because of my belief in global warming and its effects, you could not sell me a piece of property within 3 meters of sea level. When this becomes a popular view, many trillions of dollars in real estate value are going to disappear. Poof! What are going to be the ramifications of this staggering loss of wealth to a significant percentage of the populace?
I only asked in #23 that you refute #17. I have no interest in “upping the ante”. (The losses we are facing in economic wellbeing and probably personal safety and liberty with the “default SLR” are already way more than I want to bet.) I’m originally from Louisiana and very well may live long enough to see the town I was conceived in be abandoned to the Gulf of Mexico.
By the way I considered your “Don’t abuse the science” comment a cheap shot. Employ the science and tell me why post #17 is wrong. Please just don’t say “No one else has said that.” Someone is always the first person to say something whether that something is correct or not. Aaron Lewis’ statements are so out of the mainstream discovering “incorrectness” should be easy. Take your time, the floor is yours.
Thanks for your time and devotion to this educational website.
[Response: My bad - I missed the earlier comment. Apologies. - gavin]
A Jim Hansen quote from the text of his recent testimony to congress:
“In my opinion, if emissions follow a business-as-usual scenario, sea level rise of at least two meters is likely this century. Hundreds of millions of people would become refugees. No stable shoreline would be reestablished in any time frame that humanity can conceive.”
Page 2 of this document: http://www.columbia.edu/~jeh1/2008/TwentyYearsLater_20080623.pdf
Clearly the issue is not how much sea level will rise but how fast. Another Hansen paper, which I’m having trouble finding the link to at the moment is, “Target Atmospheric CO2: Where Should Humanity Aim?”. While it has been some time since I read it, the paper makes a good case based on paleoclimatinc evidence that a large proportion of the world’s ice is unstable in the long term even at current CO2 levels. Hence Hansen argues for a 350 ppm long term target.
It is probably the case that most of the GIS and WAIS are unstable at current and projected CO2 levels. If CO2 reaches 450 ppm and remains there for decades, parts of the EAIS will become unstable too. Long term sea level rises of 12 to 25 metres are reasonable under those circumstances. But how fast? If the sea is rising at 0.2 metres or more a decade, coastal urban areas, ports and other infrastructure – not to mention the heavily populated agricultural delta regions of the planet – will have to contantly respond. The challenge for human society will be unprecedented.
It will be interesting to discuss the assumptions underlying the Dutch projections of >1 m. SLR by 2100. I have seen the draft report, it will be published eventually as an annex to the Deltacommission report. Some info in Dutch on my blog.
Andrew, I looked into the coastal infrastructure in the Houston-Galveston ship channel and inland conditions where subsidence continues despite expensive efforts to reduce mining aquifers.
Bottom line for me is steady loss of 42 percent of America’s petrochemcial industry.
And, assuming much of the world’s petrochemical and oil refining capacity is also at or close to seaports, Houston will not suffer alone.
Maybe, in the not too distant future, Algeria will supply the chemicals Houston cannot. That is not good news.
Comment by John L. McCormick — 5 Sep 2008 @ 10:05 AM
Hansen’s paper last summer looked at 3 time scales — 10s, 100s, and 1000s of years — for the scary sea level rises and decided that millennial was out: the geological record showed that if the seas were to rise, they’d rise pretty fast. The most likely was a time scale of centuries, but that they couldn’t rule out decadal. Which isn’t alarmist, but is pretty scary.
5 meters = 16.4 feet, approximately. So he’s not talking about Hansen. The 20 foot number shows up two places: the famous Associated Press typographical error that was widely spread in the news and so hard to correct, and the “total melt of Antarctica” projections. (It took me multiple emails to our local SF Chronicle paper to get that mistake fixed on their website — with help from the science writer!. Editors had it repeated in the text and took out only one error each time we complained to them.)
I think the university must be trying to lessen the impact of this paper, which would be expected to draw scary-new-large-estimate headlines, coming out right during the political conventions.
Shorter press release:
“Yes, we’ve found alligators, but no ichthyosaurs, while trying to drain the swamp — good news!”
It’s an election year in the US. This makes everything weirder than usual.
I think this whole discussion (and posts #21 and #26) raises a real problem. Things will be bad in this generation, and worse in the next. The issue is the really unliveable and cataclysmic stuff – onwards and upwards to the 80m “eventually” level – is still probably hundreds of years off. And people don’t respond on an emotional level to problems that are so distant – although our actions right now (and specifically, I’d contend, our decisions at Copenhagen in 2009) may or may not make that future almost inevitable.
If our decisions right now kill billions in a few hundred years, are we any less culpable than if it were our own generation? Logically no, but I fear it won’t be seen this way…
Just to nail this down, the original error, based on error in Associated Press wire report, began thus as it appeared locally:
OCEANS RISING FAST, NEW STUDIES FIND
Melting ice could raise levels up to 20 feet by 2100, scientists say
David Perlman, Chronicle Science Editor
Friday, March 24, 2006
Glaciers and ice sheets on opposite ends of the Earth are melting faster than previously thought and could cause sea levels around the world to rise as much as 13 to 20 feet by the end of the century, scientists are reporting today….
…. The teams then compared that era to what might happen in this century …
They concluded that … would lead to an average global temperature increase of at least 4 degrees Fahrenheit and a rise from today’s global sea level of 13 to 20 feet…..
————–end excerpt from original story as printed—————–
Oops. (AP failed to state over what span of time, leaving the earlier “this century” mistakenly attached to the longer term number). Then they listed a long range of scientists as supporting the research, after grossly misstating the research papers.
OCEANS RISING FAST, NEW STUDIES FIND
Melting ice could raise levels up to 3 feet by 2100, scientists say
David Perlman, Chronicle Science Editor
Friday, March 24, 2006
Glaciers and ice sheets on opposite ends of the Earth are melting faster than previously thought and could cause sea levels around the world to rise as much as three feet by the end of this century and 13 to 20 feet in coming centuries, scientists are reporting today. …
My thanks to David Perlman who persisted until the Chron’s editors fixed the error not just in the headline but also, eventually, in the text of the article. Pity they only say corrections were made but not how and why it was corrected, eh?
For anyone who would like to explore what sea level rise would mean for the US coastline, check out this interactive map I made using the EPA’s data. It’s not the .8 meter-2meter estimate, but it’s close:
Sea level has potential to be a big problem; no doubt about that. But there are a couple of others that scare me more.
Ocean acidification has the potential to cause a breakdown of large segments of that ecosystem. How many people depend on the ocean for food?
Speaking of food, farmers will really struggle in a climate in flux. Rice, corn, wheat, etc., they all need specific and different amounts of rain and temperatures to grow well. Whatever changes are coming, there will be changes. It is not easy to switch from one thing to growing something else. Worldwide, there is not much of a food surplus now. Let us hope the changes don’t accelerate too much. How many people depend on farmers for food?
Add in the decrease in cheap energy and food production becomes even more of a problem. People crib about $4 gas; $4 (or more) bread will cause a real ruckus.
Complete layman here, with a history background, not science.
Here’s my uneducated question – while I respect Gavin’s comments about not abusing the science, it seems to me that many measurable indicators of climate change are (to the extent I can tell) occurring/progressing/worsening faster than predicted by most models, whether we’re talking about atmospheric CO2 levels, arctic ice melting, glacial retreat, etc.
Is it too much of a stretch to assume that sea levels will rise faster than currently predicted, largely because many of the factors that contribute to sea levels rising are occurring at faster-than-predicted, and possibly accelerating, rate?
Jason/Topex measurements indicate sea level is increasing at 3.2 mms per year.
In the last 15 years, sea level has increased by:
– 1 inch
If the trend continues for 100 years, sea level will increase by:
– 1 foot
Where do people get all these exagerated figures from?
[Response: Current trends in sea level rise are larger (> 3mm/year), and estimates of future changes rely on more that the excel linear regression routine. Read the papers linked to above to get an idea. - gavin]
A quicky Sandbox101 clarification: Stefan’s paper says 3.4mm/yr/degree. I do not understand the \per year\ part. If global surface temp goes up 1 degree, does the sea level rise 3.4mm per year for ever? Seems odd, but I don’t know.
[Response: My paper is here, if you want to read it. The simple approach is only valid for the initial sea level response to large and rapid rise in global temperature, as sketched in Fig. 1 of my paper. Some people have misunderstood this. Obviously this rise will not continue forever but asymptotically approach a new equilibrium. And obviously this approach will not work for the small natural sea level fluctuations found in the preindustrial centuries, since these are ruled by different physics. You have to have a big rapid global warming that sticks out well from the natural variability for this approach to make any sense at all. stefan]
Geoff Beacon wrote: “Sea level rise gets more attention than other aspects of climate change. Is that because it is the worst?”
I am more worried about drought. Even the worst-case scenarios of sea level rise suggest that it will take many years, perhaps decades, to have truly catastrophic effects (e.g. to displace tens of millions of people in coastal areas).
On the other hand, another effect of global warming, namely massive, continent-wide, intense, persistent drought, could begin at any time and have catastrophic effects on agriculture, leading to widespread famine within a few years. Indeed there is evidence that such intense, chronic drought may already be kicking in with a vengeance in Africa and Australia, as well as parts of North America.
Surely this is a more urgent and imminent danger than sea level rise, yet it doesn’t seem to get as much attention.
#44: Yes, because  one of the big problems with sea level rise is that there is very little one can do to stop it. How big of a wall are we going to build to hold off the water? How strong can we really make it? Just the eastern seaboard of the US has a daunting enough length, what about the rest of the world? And  as they mention in the post, sea level continues to rise for a significant period of time even after temperature rise is stopped or reduced.
#49–”People crib about $4 gas; $4 (or more) bread will cause a real ruckus.” I want to validate everything about your post except the timeline: the good bread I used to buy regularly hit $4 last year. I still miss it. . .
It’s always advisable to read the paper first, but the authors public comments are informative, too:
ScienceNOW Daily News 4 September 2008
“They calculated how fast glaciers would have to flow in order to raise sea level by a given number of meters and then considered whether those flow rates were plausible or even physically possible. In Greenland, they calculated ice loss through specific rock-bounded “gates,” which are carved in the edges of the island. In West Antarctica, the gates are not well defined, so the team used approximations of how flow might respond to rising temperatures….estimates of several meters of sea level rise made by some other researchers are “physically untenable” because not enough ice could be pushed through the glacial gates, according to the paper’s authors. ”
PhysOrg Sept 4, 2008
“…global sea rise of much more than 6 feet is a near physical impossibility…
Most of the marine-based ice in West Antarctica is held behind the Ross and Filcher-Ronne ice shelves, which Pfeffer’s team believes are unlikely to be removed by climate or oceanographic processes during the next century….
Policymakers need to be able to predict sea level accurately if communities, cities and countries around the world are going to be able to plan effectively, Pfeffer said. “If we plan for 6 feet and only get 2 feet, for example, or visa versa, we could spend billions of dollars of resources solving the wrong problems.”
Daily Telegraph 04/09/2008
“…estimates of future rises remain hazy, mostly because there are many uncertainties, from the lack of data on what ice sheets did in the past to predict how they will react to warming, insufficient long-term satellite data to unpick the effects of natural climate change from that caused by man and a spottiness in the degree to which places such as Antarctica have warmed….
“We simply don’t understand the physics of ice dynamics well enough to make accurate model predictions,” says Dr Harper. “There are just too many uncertainties…”
Climatologists usually present possibilities and probabilities, here I’m pleased to see “a near physical impossibility.”
Rod B #45 yes, a very good question. Note that Stefan calls this a “semi-empirical” approach, meaning that there isn’t much physics behind it.
But there is this much physics behind it: both the melting of glaciers and the warming of ocean water is driven by the imbalance between incoming and outgoing heat energy. As a proxy for this you could take the difference between current mean temperature and the equilibrium mean temperature for current forcing. But as we well know, the latter is not very well known.
So, instead, StefaSo, instead, Stefan takes current (realized, transient) mean temperature excess. In the simplified situation where the excess forcing grows exponentially, this quantity is proportional to the excess forcing, as well as to the above described heat imbalance. For the 20th century the assumption of exponentiality is roughly OK.
Note that this is the same kind of idea that was behind Pat Frank’s writing, only there it was a fallacy ;-)
You are right, drought is right up there as one of the worst problems associated with AGW. I don’t know. Some RC regulars may know that I am very sensitive about drought around the Med, but sea level rise is a pretty nasty problem too. Maybe our moderators can provide some perspective?
Some people appear to think that we are balming (sic) the media for the misleading headlines on this story. That is certainly not the case since most of the spin originated from the press release (as we stated clearly above). It is unfortunate that these headlines arose because they will mislead, but it is not because of the ‘bad media’ (though many stories did see past that press release). Pielke makes another error in equating thought experiments (as performed by Hansen in his ERL paper) with an informed prediction. Postulating a non-linear doubling process in order to get an order of magnitude estimate is not the same as making a prediction as he makes very clear, and later in that article, he states what he fears may happen (quoted above). Pielke might think that the Pfeffer et al constraints are reduction in the projections, but as we have stressed numerous times, the projections that matter are the ones that come out of the assessment processes, not from the musings of individuals (however their sometime ambiguous pronouncements are interpreted). With many people (linked above), still incorrectly insisting that sea level won’t rise above 10cm in a century, these latest constraints should be sobering. We’ll see.
You would be better served by simply correcting your silly claim that “no-one (and we mean no-one) has published an informed estimate of more than 2 meters of sea level rise by 2100″. Anyone can read Hansen and see that he thinks that his estimate was “informed” and likely to be more “better estimate” than Rahmstorf’s approach for 2100.
I have little confidence in the ability of the scientific community to accurately predict sea level rise — though the constraint approach by Pfeffer et al. helps move beyond the prediction problem. After all the 1990 IPCC grossly overestimated sea level rise to date:
If there is anything to take issue with in the Colorado press release it is the idea that decision makers can optimize a response to sea level rise, they cannot.
[Response: Roger, my interactions with you are always singularly unproductive and so my patience in pointing things out to you is limited. Having said that, please read the line in the above post (third paragraph from the bottom) that starts "(exemplified by...". Perhaps you missed that earlier, but in case it still isn't clear, we were pointing out how the spin in the Reuters piece took a very clear lead from the press release. So it's not "now" that the press release is an issue it was "then". Are you even disputing this? And as for IPCC AR4 not making statements about sea level projections, I have no idea where you get that notion (see section 10.6 in WG1). We might be able to agree that they were inadequate or poorly communicated, but not nonexistent. - gavin]
Comment by Roger Pielke, Jr. — 5 Sep 2008 @ 4:08 PM
re no 25. I was in Thule AFB in Greenland for 2 weeks around the end of August. In 14 days, we had perhaps 4 days where it did not rain.
I was speaking with a few local workers at the base, who indicated that the tongue of the glacier visible about 30K west used to be almost at the end of the runway 10 years ago.
Interestingly enough, we were not able to resupply one arctic location as the runway was too soft for landings (2nd year ever it happened) and had to stop a couple of days at our main location as the top of that runway softened due to the landings and the constant wet snow and drizzle (Alert).
“Sea-level rise from melting of polar ice sheets is one of the largest potential threats of future climate change. Polar warming by the year 2100 may reach levels similar to those of 130,000 to 127,000 years ago that were associated with sea levels several meters above modern levels; both the Greenland Ice Sheet and portions of the Antarctic Ice Sheet may be vulnerable. . . Corals on tectonically stable coasts from the last interglaciation period (LIG) provided strong evidence that sea level was 4 to >6 m above present levels during a sea-level high stand that likely lasted from 129,000 ± 1000 years ago to at least 118,000 years ago.” http://www.sciencemag.org/cgi/content/full/311/5768/1747
From the NCAR press release:
“Ice sheets across both the Arctic and Antarctic could melt more quickly than expected this century, according to two studies that blend computer modeling with paleoclimate records. The studies, led by scientists at the National Center for Atmospheric Research (NCAR) and the University of Arizona, show that Arctic summers by 2100 may be as warm as they were nearly 130,000 years ago, when sea levels eventually rose up to 20 feet (6 meters) higher than today.” http://www.ucar.edu/news/releases/2006/melting.shtml
[Response: You aren't reading carefully (though both cases could have been much better worded). The polar warming at 2100 was projected to be comparable to Eemian warmth, but the sea level rise was a long term response with an unknown timescale. However, I'm sure it's comforting to know that you aren't the only person to get that wrong. - gavin]
Comment by Roger Pielke, Jr. — 5 Sep 2008 @ 4:34 PM
Richard C. asked at 3:48 pm on 5th Sept 2008:
“how much sea rise is required to turn Greenland’s interior into a grounded ice sheet?”
Parts of Greenland’s interior are currently below sea level. There are some pretty deep spots under Petermann , Humboldt, in the NW and Nioghalvfjerdsbrae (how does one pronounce that ?) and Zachariae Istrom in the NE just south of Independence Fjord (where the NEGIS emerges)
One meter sea level rise in a century will do no good, and potentially some harm, to the near-shore marine life community; shellfish such as clams and limpets are particularly at risk. During the transition for LGM to the Holocene the sea level rose about 120 meters over, say, 12,000 years; an average of a meter per century. During this the near-shore marine community of eastern South America, with a gentle grade to what is now the continental slope, was compeletely (or nearly so) disrupted; it only recovered during the Holocene. In contrast, the Pacific shore of South America, very steep, suffered no ill effects.
Sandy beaches: sandy beaches are the result of along-shore currents and also wave action bringing sand from production areas to dewposition ares. For example, Maine and further north are production areas for the east coast of North America; the sand is transported further south and eventually to the deposition areas of the Carolina Outer Banks and off-shore thre. (I don’t know what happens further south.)
This action won’t stop due to a 1–2 meter rise; winter storms will continue to pile up sand onto the current beach. Wherever there is sand now there will continue (mostly) to be sand. Wherever there are rocky shores that state also will (mostly) continue.
So your grandchildren will be able to go to the beach, but there will be no need to bring a spade and a bucket for clamming.
Indeed, you suggest that Hansen made an “ambiguous pronouncement” . . . Overpeck could have been “much better worded” . . .
But perhaps you could point me to the Real Climate admonishments of these scientists for their imprecision/bad writing when their work was widely misinterpreted? Or perhaps to where these scientists sought to correct the egregious public misinterpretations?
[Response: So now it's my fault? Well, we spelled out what it meant at the time. As for corrections, it's definitely happened - the original headline after the 2006 Science papers in the San Francisco Chronicle had "20 feet by 2100" or similar, the authors immediately contacted the paper and they changed the headline to something better (but not perfect) "OCEANS RISING FAST, NEW STUDIES FIND" and corrected the text from what appeared in the print edition. And RC has often criticisedpress releases for leading the press astray. I'm very much of the opinion that most of the press does a pretty good job overall given the constraints they work with, but there are fault lines that occasionally get tripped - through a combination of bad framing, or uncontextualised press releases, or naive scientists - that end up (predictably) producing vastly misleading headlines. Maybe you'd like to come to my class at the J-school where I go over these examples and more... - gavin]
Comment by Roger Pielke, Jr. — 5 Sep 2008 @ 5:05 PM
Richard C. asked at 3:48 pm on 5th Sept 2008:
“how much sea rise is required to turn Greenland’s interior into a grounded ice sheet?”
In my last comment I should have mentioned the Pfeffer paper, in Fig 1, shows the marine based outlets as including almost all the usual suspects, not just in the NE and NW.
#23 Mike Tabony asked, “Where does Slioch (#18) think the human race will get the energy and material resources to rebuild the world’s ports?”
I don’t. I was suggesting that coping with a one metre per century change in sea level continued for several centuries might be even worse than a one-off catastrophic change, since at no point would we be in a position to even begin to rebuild coastal communities and would be in a state of constant flux.
In other words, it is not just how much sea level rises, but how long it takes which is important. The latter is usually not emphasised.
Gavin, what value for “total sea level rise in the next 100 years” would you give to an engineer or policy maker that needs to be 99.9999% (1 in a million) certain that his design or policy will protect the public safety for 100 years? Not just for today, but a number we can be certain of for 100 years. If you make a mistake and people die, how many deaths can you live with? I am not being dramatic. You are a climate expert, and we need to set public policy. We need a number.
As you suggest, it rains on the flanks of the GIS. Where does that water go, how much heat does it carry, and where does it release that heat? It is a foundation engineering problem of the first water. The top of the ice sheet can stay cold, strong , and rigid, but, if the foundation fails, the whole structure fails. The flanks act as compressive buttresses to the ice foundation that supports the central massive. (Think of a concrete building tipping over as its permafrost foundation weakens.) Weaken the flanks of the ice sheet, and the ice under the massive is subject to compressive failure. Worse, it is a basin with its outlets plugged with ice, allowing the formation of subglacial and intraglacial lakes large enough to produce significant hydrostatic pressures. The problem today, is that we have both known unknowns and unknown unknowns in this system.
Pfeffer, et al’s number is not total, and it has no certainty. To be useful in planning, we need a value for total sea level rise. Without good estimates of uncertainty and defining both ‘known unknowns” and unknown unknowns,” Pfeffer et al’s is useless for engineering or public planning. If our best estimate of sea level rise contains substantial “unknown unknowns” then we might want to adopt a procedure similar to the one used by the US EPA for Human Health Risk Assessments a while back, and apply safety factors.
They would say:
“The estimated number is 2 meters, the safety factor is 10, so the maximum plausible sea level rise from Greenland is 20 meters by 2100, take precautions accordingly”.
They might go on to say:
“The estimated SLR from permafrost melt is 1 meter with no unknowns, and the estimated sea level rise from Antarctica is 2 meters with very large unknowns so the safety factor is 100. Thus, the total maximum sea level rise for public safety purposes is 221 meters. If you do not like that number, go do the research to eliminate the unknowns and uncertainties so we can remove the safety factors.”
Ahh! Those were the days when federal agencies had more . . . . funding.
If our federal agencies, said firmly, “The SLR number is 221 m. DOW, Exxon, BP, US DOE, US DOD, and so forth ; What are your plans for dealing with a 221 m rise in sea levels?” We would have the data to resolve the unknowns real fast, and we would be in a low carbon economy, real fast! True, nobody would be happy. Nobody liked CERCLA either, but it saved a lot of lives.
Are such safety factors good climate science? No! However, they are good risk management science. They are good engineering and very good public policy. Such policies protected the public health and safety from hazardous waste in the environment with unknown characteristics. Are such numbers alarmist? No, they are the basis of good,conservative engineering.
[Response: I've not consulted directly with planners on this issue, but people I know do this on a regular basis. The most questions come up when some new infrastructure is being planned - a recent example was storm drains in New York City - the planners wanted to know how high above max high tide levels they should build the drains. The factors were that the infrastructure was going to last for 50 or so years, and they didn't need a guarantee or perfect prediction but just an range that would likely keep them out of hot (cold?) water. I think that the advice was that an allowance for 1 meter additional rise over an above what their storm surge estimates gave. That's pretty conservative advice (as in erring on the safe side), but it will be much clearer in 2050 (when they are planning for the following 50 years) what the trajectory really is. Advice that no allowance for SLR was needed would have been irresponsible, advice in the mid-range of projections would not have been useful either. The point is that you can give useful advice even in the midst of great uncertainty without having to exaggerate the likely effects. - gavin]
Aaron Lewis wrote at 5:20 pm on the 5th of September, 2008:
“[Greenland] is a basin with its outlets plugged with ice, allowing the formation of subglacial and intraglacial lakes”
I suspect that some of the outlets might melt open. Is there any evidence yet of substantial subglacial lakes in Greenland? I have heard of several in Antarctica, some of them interconnected, changing sometimes on a daily basis.
“… Eventually all of Greenland’s floating ice could disintegrate. At that point the ice streams may stop accelerating. Then again, they may not, Steffen says. The weight of Greenland’s ice sheet has forced its bedrock down into a vast basin, much of it below sea level. As the glaciers retreat inland, the ocean may follow, prying them off their bed in a runaway process of collapse….” http://ngm.nationalgeographic.com/print/2007/06/big-thaw/big-thaw-text
There is a nifty interactive sea level inundation mapper at the flood.firetree.net website. Just zoom into your part of the world, select a sea level rise amount (up to 7m) and then strap on a snorkel.
For about a year i’ve been looking at the material on SLR and 3 months ago I began to summarize SLR for a friend who happens to have a house over the water (S. California). So from a real world perspective he is very interested in potentials. I spoke with a friend at Scripps and he said a cm is a cm regarding wave height, but related the problem of potentially stronger storms in our region as ocean temps rise.
To my friend, I basically started by saying his question is one of the most difficult to answer scientifically. And I did resort to what you referred to as “male up even scarier monsters” with a high concentration on the uncertainty in that realm (I was careful when discussing the dragons). My objective was to show him the scientific analysis IPCC and Stefans paper and then compare that to Hansen, current SLR observed and paleo record as currently understood re. past SLR and estimated temps, GHG levels, length of time at those levels and hypothesized negative feedbacks such as cloud albedo, even though it seems the climate system managed to get past such effects in the past and of course feedbacks and non linear potential.
Along the lines of the Arron Lewis question in comment #63, if you feel it is plausible, can you characterize the risk potentials based on the following considerations:
The PDO is supposedly entering a cool phase, or finishing its warm phase, for eastern pacific, and still we had an unusually strong El Nino event with significant coastal erosion.
Is there a scientific way to discuss the potential or likely effects such as storm damage rather than SLR, since that is the greater immediate danger as far as I can tell pertaining to ocean temp rise increasing storm strength a as opposed to SLR for the eastern pacific, i.e. specifically the west coast. It’s obvious the gulf and Atlantic regions will get stronger storms but the Pacific has a different tempo and being a larger body, slower thermal inertia.
So then, just as models indicate stronger hurricanes generated in the Atlantic, Is it then reasonable to expect higher potential for a similar El Nino event to the 98 event, especially considering the likelihood of increased solar forcing when the Schwabe cycle gets back into gear? Was the 98 event just an El Nino riding on top of the global warming wave, or an even more significant event? I’m not sure how to talk about this? Because if that event was more signal than noise, so to speak, then the next one could be even stronger. Or is this too much weather talk and not enough climate?
> where these scientists sought to correct the
> egregious public misinterpretations?
I recall the original error was in the Associated Press wire story. By the time I contacted the SF Chronicle science writer Perlman, if I recall correctly, he had already heard about the problem (as Gavin points out, someone was trying to catch the error). He’d told his editors — but they hadn’t done anything. He told them again; they changed the headline. They didn’t change the text. We exchanged more email. He told them again. They finally changed the text. Way too late.
Wasn’t this AP wire story and error correction talked about on Pielke’s blog at the time? Oddly it’s impossible to find mention of it with Google, for me.
Anyone know where the Associated Press keeps their errata and corrections list, presuming they have such a thing? Andy Revkin might know.
Good response. Seems you have learnt a little engineering. Lots more similar understanding may be needed. Hint: Setting levee crest levels is tougher. Overtopping is (literally?) a “tipping point”. It tends to kill people.
The effects of a 1 or 2 metre SLR over a century is not a big deal compared to the changes we’ve made to coastlines over the last century, much of New Orleans was below sea level when it was built, and Man’s engineering abilities are far greater now than they’ve ever been.
As for 100 million displaced, how many people have been displaced as a result of human factors over the last century, I’ll bet more than 100 million.
Not disputing than AGW’s happening, or that the effects of some of the changes may be dire, but can we please be realistic about what the numbers actually mean?
For storm drains in NYC, a SLR of 1 meter is a cost effective design criteria.
Do not get me wrong, I love good storm drains, but there is no law saying NYC storm drains must be designed to withstand 200-year return event storms. Thus, PE liability and bonding issues are minor, and the value of enhanced storm drains is limited by the vulnerability of legacy infrastructure.
The question stands. What is the value for SLR that you are 99.9999% sure will not be exceeded in the next 100 years?
“Debate among scientists is only about how much sea level would rise by a given date. In my opinion, if emissions follow a business-as-usual scenario, sea level rise of at least two meters is likely this century.”
Maybe RC needs a media contacts address book, so corrections can be e-mailed to science reporters. Maybe they’ll eventually start viewing press releases with a more critical eye, or even wait a day for some third-party analysis. :-)
This discussion seems to drift between Artic ice conditions and sea level rise.
Well global ice is maimly concentrated in the SH not the NH! Not that you would realise that from most of the posts here.
As far as sea level rise is concerned there is absolutely no evidence of an accelerating trend, which would be necessary, for some of the dire predictions, stated here, to come to pass. Indeed sea levels have been stable for 2 or three years now. how come?
I just noticed something about the press release. It notes that “Some scientists have theorized that continuing warming trends in Greenland and Antarctica could warm the Earth by 4 degrees F over the present by 2100. The last time that happened, roughly 125,000 years ago during the last interglacial period, glacier changes raised sea level by 12 to 20 feet or more. But the time scale is poorly constrained and may have required millennia, Pfeffer said.”
I thought 4 degrees wasn’t exactly at the extreme end of the IPCC projection range, and that the IPCC would constitute more than just “some scientists”. Am I mistaken? And do we have a reliable estimate of the rate of temperature change during the LIG, and how it compares to projections for this century?
Roger Pielke, Jr in #55 states that the IPCC’s first assessment report “grossly over-estimated” sea level rise to date. I see a link to his own blog, but I cannot check the original report as it is not online (and the Wikipedia summary a rather hopeless stub, which I hope can be improved upon). As a layman, I’d expect to see a range presented, but on Roger’s blog it is a single trajectory for each report (with the first report over-estimating, and the following two underestimating).
Could someone expand on what was actually in the original 1990 report? Is Roger’s summary fair? Specifically – what is each line on his chart – the average forecast? The maximum? And was there a projection for the century? Obviously the first report was based on much less research than followed even four years later (let alone right now), but just interested in getting a better historical conext for this latest paper following Gavin’s thoughts – thanks.
[Response: We've had this discussion before with Pielke, about the temperature projections of the first IPCC report. Gavin can probably quickly find the link. The key point is that the first report included only the warming effect of greenhouse gases, but not the cooling effects of anthropogenic aerosol pollution. You have to remember that scenarios are not predictions, but "what...if" type calculations. What would happen if greenhouse gases rise by that much? Thus, as a calculation of the warming and sea level rise that these greenhouse gas emissions would produce (by themselves), this may well have been correct. But there was an additional effect that IPCC did not include in the scenarios at the time, namely the aerosol pollution. Hence these scenarios were not realistic, even if technically the estimates were correct. -stefan]
As the glaciers retreat inland, the ocean may follow, prying them off their bed in a runaway process of collapse
I must confess I’ve never understood this particular prediction of doom. If the ocean is able to “pry them off their beds”, it follows that they must already be sufficiently far below sea level that they would float. And if they’re floating, then the sea level rise from melting them is zero. Surely it’s exactly the other way round – the deeper below sea level the Greenland bedrock is, the better?
To quote from above, “…no-one has published an informed estimate of more than 2 meters of sea level rise by 2100.”
Firstly, Hansen is on record as expecting a SLR of more than 2 metres under BAU – see my post #30. I accept this does not appear in a peer reviewed publication.
Secondly and more importantly, when it comes to the cryosphere, informed estimates have so far proved to be gross underestimates. Prior to 2007 the informed consensus was for artic sea ice to be gone in mid summer between 2050 and 2100. Now some scientists have “informed” expectations that this will happen within 5-10 years and 30 years is a reasonable consensus.
As you well know, projections of global temperature rise are underpinned by sound physical models that have proven reasonably accurate since Hansen’s 1988 paper (if not earlier). But projections of SLR is not underpinned by sound understanding of the physics of ice sheet collapse.
Until models can reproduce the gyrations in SL over the last 100,000 years or so – including the 5 metre per century rise over 4-5 centuries during “Meltwater Pulse 1A”, one wonders what value peer-reviewed “informed” estimates have. (Peak rates were probably greater than 0.05m/yr.)
Until then surely we can really only attempt to “constrain” the range of expected SLR. (Pfeffer’s paper appears to be an attempt to do this – I can’t access it to check.) Using the IPCC lower bound would be a reasonable, although highly unlikely, lower bound SLR. The maximum might best be determined by paleoclimatic-geologic estimates – at least they *really* happened.
Meltwater Pulse 1A occurred under substantially less forcing than we currently have, but it almost certainly was preceded by millennia of “build-up”. So, on balance, 5 metres by 2100 is a reasonable, perhaps equally-unlikely, upper bound.
This gives a range of SLR from 0.2 to 5 metres by 2100.
One meter sea level rise in a century will do no good
Note, also, that one meter of sea level rise is enough to make many, many coastal cities uninhabitable. All the seawater has to do is back up sewers and seep into aquifers, and bingo — you’ve got a city nobody can live in, unless they take special equipment with them.
For those who are interested, the ongoing Thames Estuary 2100 project has involved intensive research into how London’s resilience against flooding can be maintained/improved over the next century (and somewhat beyond). The Consortium have indicated confidence that, through the implementation of a portfolio of measures, it is possible that the greater part of London could be protected against 5.25m of sea level rise; contingent on the development of effective decision-making, financial and construction plans (e.g. Thames Barrier 2.0) and processes within an adequate timescale.
Paper is not online but full citation is:
REEDER, T., WICKS, J., LOVELL, L. & TARRANT, O. (2008) Protecting London from Tidal Flooding: Limits to Engineering Adaptation Paper presented at the Tyndall Centre for Climate Change Research Conference “Living with climate change: are there limits to adaptation?” 7th & 8th February 2008. RGS, London.
I recall reading somewhere that it would take decades for sea level
rise occasioned by ice-sheet melt to reach distant coastlines like
those of South Asia. Is this true? It seems implausible, but if true,
it gives valuable time.
[Response: No. Most of the sea level rise travels as a gravity wave (like a tsunami) which would go around the world in a day or two. There certainly are longer term adjustment processes that work slower (and a paper recently by Stammer discussed this). - gavin]
Ref 63, 73 on probabilities and risk factors for use in design.
Thanks for raising this point. It is critical to the response of policy makers.
Factors of 10 or 100 appear to be a bit extreme, particularly when dealing with a 50 or 100 year life (as would be the case for infrastructure. Normally, in the world we knew a couple of decades ago where the environmant was basically stable, we would take the bell curve of data such as wind speeds (extreme values of these above some cut-off) and say that for safety we will assume the 95th percentile value is suitable for design. Then a design event would be chosen that would typify this level of probability of the wind (or other event) being exceeded within the life of the structure.
In practice due to the conservatisms used in the design and construction process the true safety factor for structures has been of the order of 5 or more above this event. In fact the real safety factor is often not known as we don’t have enough data on building collapses to determine it. Buildings often fail not due to the design being too low, but the details of construction being lacking in some way.
A method has been derived that sets a ‘reliability’ level for the structure and this is used to determine the probability values used for design. There is a lot of mathematics in this method and not relevant here in this blog. However, for the simplest approach, structures are designed for an ‘event’. Drainage might be designed for a 1 in 20 or 1 in 50 year event (based of course on the “stable” climate we all know). Buildings are dsigned for winds of the order of 1 in 500 year event and earthquake is similar (with an additional look over the sholder at the 1 in 2000 year earthquake in high risk areas such as California).
If we start to look at SLR, we might say that we should take the 95th percentile of the upper extremes of the peer reviewed ranges provided in the last say 2 year period (rounded to a logical value). It would seem appropriate to then make some assessment of the rate of change in such predictions over the last 5 years to see if there was some adjustment to be made. On the basis of this there may be an additional factor put on the 95th percenbtile value as a sort of “uncertainty” factor for safety reasons.
A review process would be necessary to adjust the “design value” given emerging new data and better predictions. Such adjustment may allow for a reduction in the uncertainty factor while raising the 95th percentile number, thus leading to a best approximation of the likely value as understood at the time it was set.
From a very limited understanding of the current range of predictions (please correct me if you know of further info), I would say the value should be of the order of 0.5m for 2050 and 1.0 for 2100 with an additional factor of 2 for 2050 and say, 3 for 2100; giving
1m for the 50 year design
3m for the 100 year design
These design values would have to be revised on a 6 mth or yearly basis at the moment, as the information available is changing so rapidly. Personally, the IPCC should be giving us a report every 1 or 2 years, not every 4. Knowledge is changing to quickly in this area.
There are a few places on Earth that are below sea level where inland seas have evaporated away, like e.g. Death Valley. If we flood these areas again and recreate the inland seas, we can lower sea levels.
[Response: Yes. but do the math - to get rid of 1 m of sea level from 70% of the globe is a lot of water. You would have to flood a lot more than Death Valley and the Dead Sea. Something more like Montana/Ontario and Quebec to recreate the paleo-Lake Agassiz for instance. - gavin]
#78 inline response – thanks Stefan, that helps enormously. Am I right in thinking, then, that really the IPCC have only made two sets of outright all-encompasing predictions, then – in 1995 and 2001? 1990 was a scenario, and 2007 left out dynamic ice sheet processes completely because they were so uncertain.
From my reading of Roger’s blog, I guess he’d interpret the “scenairo” 1990 explanation as spin. I’ve no reason to doubt that the 1990 and 1996 processes were quite different, and exactly as you say, although I don’t have access to the reports. I’d hope that those writing reports – especially IPCC ones – would flag up very clearly important distinctions such as this one (I didn’t realise that the critical significance of the different methodology in 2007 until Real Climate pointed it out). And I’d hope that all climate scientists would help get these sorts of messages across to clarify to the public, rather than point score based on comparisions which should not legitimately be made.
Aaron, your question
> What is the value for SLR that you are 99.9999% sure will not be exceeded in the next 100 years?
indicates you haven’t taken a statistics course. Look up ‘long tail’ for pop science articles that may be helpful.
William Connolley would have fixed “pry them up off their beds” if that had been from Wikipedia (where someone had the glaciers dragging themselves out of their beds).
What the National Geographic writer was waxing (or waning) poetic about is this: the Greenland ice, like the Antarctic ice, has piled up quite high above ground and above sea level —- look at the elevation of the top of the ice in both cases.
Yes, ice floats. But if you take a cubic foot block of ice and put it in water an inch deep, it doesn’t float. It rests firmly on the bottom of the container. You can look up “basal temperature” and “subglacial lakes” for more — at the bottom of these huge thick piles of ice there are often voids or layers of meltwater just from the pressure, but the pressure is still enormous. Maybe enough to ‘float’ the ice or maybe enough to force any fluid there to move ‘uphill’ if a route is available. It’s not just sitting there inert.
Thanks, Martin (50) and Bruce (83), but my question remains. It sounds like Stefan is saying if global surface temperature increases one degree (and then stays there forever) oceans will then rise 3.4mm each and every year hence. Doesn’t sound right. Actually seems impossible. What does he (the units) really mean?
It sounds like Stefan is saying if global surface temperature increases one degree (and then stays there forever) oceans will then rise 3.4mm each and every year hence.
Yes it does, doesn’t it. But that’s precisely the misunderstanding you shouldn’t make as I tried to explain. Caveat, I cannot access the article, but am somewhat familiar with the theory.
In the general (not: 20th century exponential) situation the proportionality that should exist is not between sea level rate and anomalous temperature (your one deg), but between sea level rate and disequilibrium, say, the warming that is still “in the pipeline”.
If warming stops at +1 deg, then the warming “in the pipeline” will start decreasing at that point, going asymptotically to zero. And so will the sea level rise rate do.
This is actually compatible with the paleo observation that every forcing situation has not only its own equilibrium mean temperature, but also its own equilibrium continental ice situation and equilibrium sea level. Change the forcng, and all of these will start changing to a new equilibrium, which will not depend on the history of getting there, only on the amount of forcing. (Ideally; Snowball Earth is an exception.)
I know this is tricky. Try thinking house, furnace, thermostat, temperatures in different rooms. Sea level is but a special proxy of global mean temperature.
Barton Paul Levenson wrote: “… one meter of sea level rise is enough to make many, many coastal cities uninhabitable … enough to make Miami, Jacksonville, and many other coastal communities around the world uninhabitable, along with much of Florida and Bangladesh.”
I’d note that coastal areas may become economically uninhabitable long before they become, literally, physically uninhabitable. I am thinking for example of the American southeast — Florida and the Gulf coast region — which will be impacted not only by rising sea levels but also by more large, powerful hurricanes. Well before it becomes physically impossible for people to inhabit these places, it can become economically impossible to inhabit them, given the enormous cost of not only holding back or retreating from the gradually rising sea level, but of repeatedly and frequently rebuilding in the aftermath of huge, powerful, massively destructive storms.
Yes, ice floats. But if you take a cubic foot block of ice and put it in water an inch deep, it doesn’t float. It rests firmly on the bottom of the container.
Well yes, that’s kind of my point. And adding another inch of water doesn’t pry it off the floor either. It doesn’t actually rise off the floor until you’ve added about 9/10 of a foot of water, at which point of course it will begin to float. And at that point, if the block melts, it won’t make the water rise any further.
To turn the same situation on its head, say you have a nice flat sheet of water, and a 1 foot cube of ice sitting on a table at sea level. Melt the ice, the water level will rise. Now say you have a nice flat sheet of water, and a cuboid 1x1x10 feet of ice floating vertically in it. You have the same 1 foot cube of ice exposed above sea level, but this time when you melt it there is no sea level rise because it’s already floating.
I can’t see why the same doesn’t apply to Greenland. The more of the ice there that’s already below sea level, because of crustal depression, the better: it means less sea level if the ice does melt out. And yet the fact that the centre of Greenland is below sea level is often raised – on this blog and other sites – as a concerning factor in regard to sea level rise.
Is it simply that the rate of sea level rise may be higher if the glaciers/ice sheet are grounded below sea level? I can see that in that circumstance, a rise in sea level would increase buoyant forces – and reduce friction between the ice and the bedrock, allowing for faster outflow?
Captcha fortune cookie: Rickman Valera. An odd couple that might have revolutionised the course of Irish independence. Or maybe not.
[Response: The issue is different. For glaciers that are grounded below sea level, there is generally a cavity below the glacier tongue and a point at the back of the cavity (the grounding line) where there is a transition between floating and grounded ice. As I understand it (and this could be corrected by someone who actual knows something), the ability of the ice stream to sustain shear changes radically at this point - floating ice (I think) has no shear (velocity differential in height), while grounded ice does (it moves faster at the top). Therefore, as the water warms and the grounding line retreats, the part of the ice that was grounded now starts moving much faster delivering more ice to the ocean. Grounding line stability is a big unknown and for some glaciers, once the old one is released, a new might not form until the glacier has retreated kilometers up the fjord. The issue with WAIS and for a significant chunk of Greenland is that in extremis, it might not stop at all (until all of that ice is spread out and floating). (Please someone correct me if I have this wrong!). - gavin]
Rod, I see now that Stefan Rahmstorf’s paper was put on-line. It’s even simpler than I thought it would be. Obviously the problem with the approach outlined by me is, that warming “in the pipeline” is not observable, and using model computations to construct it introduces model uncertainty… then it is a good question if the method is anymore worth applying as compared to direct model simulations. Still it might be a useful consistency check.
The issue with WAIS and for a significant chunk of Greenland is that in extremis, it might not stop at all (until all of that ice is spread out and floating).
Nope, sorry, still can’t grasp this. You can’t float a significant chunk of Greenland until you get to the point where melting that chunk doesn’t cause any sea level rise. That’s what floating is (modulo fractional changes due to differing density of saline/fresh water, but that’s not what we’re talking about).
Say we have a shallowish tray a couple of inches deep, with your 1-foot cube of ice sitting in the tray. That corresponds to the Greenland ice sheet, sitting in a depression in the bedrock. There are a couple of cracks in the tray rim where ice is oozing out. The tray is sitting in water, which is gradually rising up the sides as the sea level increases.
As the sea level rises closer to the rim of the tray, I can buy that it might make the streams of ice move faster. I think your point about shear is simply a restatement of my “less friction with the bedrock” in other words – it’s the friction with the ground that causes shear.
As sea level continues to rise, it will eventually overtop the rim of the tray – i.e. the grounding line of the glacier moves far enough back that it reaches the part of the ice sheet that is below sea level. That will not magically float the huge cube of ice in that tray. You just cannot float the Greenland ice sheet until you have already attained the 7m sea level rise you’d get from melting it down! It doesn’t make physical sense.
[Response: You are assuming that the ice sheet retains the same shape. It doesn't. Imagine your ice cube suddenly becoming much thinner - now all of it is floating, and everything that was above sea level (minus 0.1 times the amount below sea level initially) has added to the water being displaced. (Note that we are really talking about WAIS, only a small part of Greenland is drained in such a manner). - gavin]
…and Rod, I committed a thinko above. It is true that both the temperature “in the pipeline” and the sea level rate “in the pipeline” go asymptotically to zero under constant forcing — but in completely different ways.
The temperature change “in the pipeline” is about half of the total temperature change, and most of this comes out over decades, only a small fraction over centuries.
For sea level rise, however, as for the volume warming of the ocean, the amount “in the pipeline” is almost all of it, and it will take many centuries to fully come out. Like warming up the deep ocean, and melting continental ice sheets do.
What this means is that Stefan Rahmstorf’s approximation (temperature anomaly == imbalance) isn’t really an approximation at all, but pretty realistic: any sea level rise that we start now by elevating global mean temperature will go on “forever”, many many centuries, before levelling out.
In subsequent posts there I’ve quoted and cited what I did find when I tried my usual amateur frenzied reading on the subject. There’s quite a bit, and a lot of change in the literature. Go forward from anything I cited, it’ll be outdated already.
You are assuming that the ice sheet retains the same shape. It doesn’t. Imagine your ice cube suddenly becoming much thinner
Hmm, but it can’t become much thinner without also becoming much wider, so yet again I think we’re approaching the same point from a different angle – which is that the sea level rise and grounding effects are about speed of outflow rather than any kind on magical non-physical “prying up” of a grounded chunk of ice.
[Response: It would obviously get wider too, but yes, there is no magic here. - gavin]
Good post, minor quibble: I’d call dynamic sea level rise, a known issue of unknown quantity, a “known unknown”, not an “unknown unknown”. Something that completely surprises us, say the Antarctic ozone hole prior to its discovery, would fall in the latter category.
Stefan is correct that the IPCC 1990 did not include important effects in its predictions (as my piece mentions). That did not stop the IPCC from calling its 1990 conditional predictions “best estimates”. Stefan is also right when he says that projections are not predictions, but this is true only when looking to the future (i.e., when the relevant emissions pathway is unknown). Looking backwards it is possible to accurately identify the emissions pathway and thus select among the conditional predictions the one that best matches. If you don’t like the word prediction then use “best estimate” as used by the IPCC. The point still holds.
As far as discounting those predictions from models that that fail to incorporate all known forcings, then of course nothing would qualify as a prediction, since no model is comprehensive. ;-)
The data shows that sea level rise is difficult to predict over the short term (since 1990), for the longer term, time will tell. But the lack of stability in published sea level predictions suggest that this is a really hard problem. Pointing that out based on experience to date would seem perfectly fair.
Comment by Roger Pielke, Jr. — 6 Sep 2008 @ 7:16 PM
“I’d note that coastal areas may become economically uninhabitable long before they become, literally, physically uninhabitable. I am thinking for example of the American southeast — Florida and the Gulf coast region — which will be impacted not only by rising sea levels but also by more large, powerful hurricanes. Well before it becomes physically impossible for people to inhabit these places, it can become economically impossible to inhabit them, given the enormous cost of not only holding back or retreating from the gradually rising sea level, but of repeatedly and frequently rebuilding in the aftermath of huge, powerful, massively destructive storms.” Secular Animist
Here’s where insurance companies and the governments can make hurricane and flood insurance near the rising coastlines illegal or prohibitively expensive. The super rich can have their 1000 acre coastal estate and insure it themselves. Everyone else, easily replaced summer shacks or less.
Good news: they rule out more than 2 meters of sea level coming from *Greenland alone* in the next century.
Can someone tell me what we’re missing here?
Until that is resolved, I’m still going with Hansen’s speculation.
We are in the midst of the fastest global warming ever recorded in the paleo record short of an asteroid impact. *Greenland Alone*?
Surely somebody has got an agenda here. Maybe somebody who has actually read the paper can tell us why any such *back of the envelope* calculations are meaningless here, and why we should wait for Cryosat II and some radar measurements to straighten this out.
Martin, thanks for the input. I think I have it now. The units [mm/yr/degree] are still misleading/inappropriate. Though I have no better suggestion; mm/degree would be just as misleading/inappropriate. How ’bout “mm/degree/some-time” :-?
Re: 110 and others
Much of the low lying Gulf of Mexico coast in Mexico, Texas, Louisiana and Florida is lightly inhabitated and consists of very large conservation areas. This includes the Laguna Madre (Mexico and Texas), Padre Island (longest barrier island in the world), half a million acres of wildlife reserves in Texas and much larger wetland areas in Louisiana and Florida and the Florida Everglades. It isn’t rich people’s homes that will be lost in the initial stage of AGW driven sea level rise, but rather some of the continent’s most important natural lands. There’ll be a lot fewer birds in NA unless something drastic is done; now.
Wright, A. P., M. J. Siegert, A. M. Le Brocq, and D. B. Gore (2008),
High sensitivity of subglacial hydrological pathways in Antarctica to small ice-sheet changes, Geophys. Res. Lett., 35, L17504, http://dx.doi.org/10.1029/2008GL034937 6 September 2008
Walker, R. T., T. K. Dupont, B. R. Parizek, and R. B. Alley (2008),
Effects of basal-melting distribution on the retreat of ice-shelf grounding lines, Geophys. Res. Lett., 35, L17503, http://dx.doi.org/10.1029/2008GL034947 5 September 2008
Geirsdóttir, Á., G. H. Miller, N. J. Wattrus, H. Björnsson, and K. Thors (2008),
Stabilization of glaciers terminating in closed water bodies: Evidence and broader implications, Geophys. Res. Lett., 35, L17502, http://dx.doi.org/10.1029/2008GL034432 3 September 2008
Haas, C., A. Pfaffling, S. Hendricks, L. Rabenstein, J. Etienne, and I. Rigor (2008),
Reduced ice thickness in Arctic Transpolar Drift favors rapid ice retreat, Geophys. Res. Lett., 35, L17501, http://dx.doi.org/10.1029/2008GL034457 3 September 2008
The time-scale of an infrastucture investment is important. In the case of the storm drains in NYC, 50 years could make sense. But, the most important decisions we are making right now are the ones that need to extend beyond 2100. A coastal highway could be abandoned but a nuclear plant requires cleanup as part of its decommissioning. Current plans for new coastal plants anticipate 60 year operating lifetimes which presumably would be extended by 30 years just as our 40 year plants are extended by 20 years. So, a plant that starts operating in 2023 will want to close finally in 2113. Allowing 30 years to cool down before decommisioning and a 20 year decommisioning process, that puts our concern about sea level rise out to 2163. So, decisions that are being made today need to be informed about what to expect well beyond 2100. British Energy, when considering the problem, only looked at low estimates of sea level rise, but perhaps, since nuclear power requires the furthest planning horizon, they should be taking a larger safety factor.
#111 – Roger, your linked article there seems to cover things fairly, and my take on what you are saying there is that “differences between estimates / predictions need to be explained better and we need a lot more research”, which sounds absolutely fine (and of course this new paper is an important step in addressing this acknowledged problem in terms of research). But to this layman’s eyes your blog strikes the opposite tone when you state, re the previous IPCC estimates / predictions, “Rahmstorf et al. interpretation of the results is little more than spin”. I don’t have access to their full paper, but on the basis of your own wider explanation, their abstract seems entirely correct. 1990 is evidently only an partial estimate, not a full prediction, and so therefore cannot be fairly compared like-for-like with the others (you concede this point in the data for 2007, so why not in 1990 as well?) The only meaningingful comparisons with predictions that can be made are those from 1996 and 2001, both of which attempted to include all relevent forcings, and both of which have underestimated observation, the contention of their paper.
So forgive if I have misunderstood, but… which is it? Spin or valid differences which require explanation? On the one hand you seem to be engaged in a useful attempt to clairfy differences in complex data, on the other you seem to infer that there are bumbling scientists who just keep changing their minds all the time and try to cover it up. And, particularly to the layman, it is sentances like “little more than spin” that leap out and create the impression that there are dark forces at work, which certainly appears not to be true. Perhaps a little more linguistic care is called for?
[Response: The paper you want to have access to is here. Don’t know what might be spin about it, but then I don’t read Roger’s website, so I wouldn’t know. Stefan
Mike Tabony #23; Thanks Mike, methinks no one wants to talk about the gorilla in the room.
But Hansen does:
“More ominous tipping points loom. West Antarctic and Greenland ice sheets are vulnerable to even small additional warming. These two-mile-thick behemoths respond slowly at first, but if disintegration gets well underway it will become unstoppable. Debate among scientists is only about how much sea level would rise by a given date. In my opinion, if emissions follow a business-as-usual scenario, sea level rise of at least two meters is likely this century. Hundreds of millions of people would become refugees. No stable shoreline would be reestablished in any time frame that humanity can conceive.”
Dr James Hansen: Global Warming Twenty Years Later: Tipping Points Near. 2008. http://www.columbia.edu/~jeh1/2008/TwentyYearsLater_20080623.pdf
Note that the Dutch Deltacommittee estimate is a *plausible upper bound*, not a best estimate. The “most plausible” estimates of sea level rise for the Netherlands in 2100 are 35cm to 85cm, based on the same scientific input as used for the 120cm “plausible upper bound” that was published last week. See http://www.knmi.nl/klimaatscenarios/aanvullend/DC/ for a list of differences.
Comment by Geert Jan van Oldenborgh — 7 Sep 2008 @ 3:53 AM
“It’s enough to make Miami, Jacksonville, and many other coastal communities around the world uninhabitable, along with much of Florida and Bangladesh.”
Only if nobody does anything for a hundred years.
And how much do you think they will have to spend to rescue all those cities and all those areas? It won’t be free. And since there will be more violent weather along coastlines, it won’t stay put very well, either. For instance, I think it’s futile to keep rebuilding New Orleans.
Roger #111, what makes you believe that the information left out will make one specific significant change? What makes you believe that there is no other left out information that will not change YOUR appraisal of what will happen.
If you cannot say, then maybe the only thing that can be done is to assume that these unmodelled activities will add some change either positive or negative to the predictions made without their inclusion.
I don’t understand what this discussion is all about? Everyone makes mistakes. But the people who wrote this paper http://www.sciencemag.org/cgi/content/abstract/321/5894/1340 didn’t make any! Being from Europe, I know why Mr Rahmstorf could make his statement “our own Stefan Rahmstorf used a simple regression model to suggest that sea level rise (SLR) could reach 0.5 to 1.4 meters above 1990 levels by 2100,”, which is 0.9 meters above IPCC highest probable “estimates” from their last report.
In european discussions people were told, that they would knowingly desinform people, when they explain, that sea level would only rise by 0.3 to 0.5 meters until 2100. This information had just been released by the IPCC. Why have those people been insulted by people who “discuss” the same way that Gavin does here on realclimate?
Who is right? The 2000 scientists of the IPCC or Mr Rahmstorf with his “very new and own” estimate?
I can’t believe what I read again here in this thread! Is climate science the science of insulting people who just reproduce what they have read from climate scientists? Or is climate science the science of never making any mistake in at least 20 years?
Everyone who reads this thread must think that every kind of science is just a joke. The longer you follow the scientific debate about climate change the more you must respect people like Roger Pielke! Sorry, Mr Gavin, this is not science any more!
[Response: I have no idea what point you are making - we did not criticise the Pfeffer et al paper in any respect, and I fail to see where anyone has been insulted. - gavin]
Stefan is correct that the IPCC 1990 did not include important effects in its predictions (as my piece mentions). That did not stop the IPCC from calling its 1990 conditional predictions “best estimates”
You say this pejoratively. Why, Roger? (I can guess). If it’s the best science can do at the time – we’re talking eighteen years ago – then indeed, it’s a best estimate, and there’s no reason for you to sneer at their being called that.
“Yes. but do the math – to get rid of 1 m of sea level from 70% of the globe is a lot of water. You would have to flood a lot more than Death Valley and the Dead Sea. Something more like Montana/Ontario and Quebec to recreate the paleo-Lake Agassiz for instance. – gavin]”
There is a surprisingly big area of the continents that are below sea level, for instance the Qattara Depression in Egypt, and vast areas in central Asia. I estimate very roughly that these areas could cope with about a metre of sea level rise. They also supply an opportunity. They could possibly be filled by pipelines operating as syphons, and the flow could be used to generate power. The flow would not cease as the depressions fill as there would be evaporation to replace. Furthermore the potential reservoir size will increase somewhat as the weight of water depresses the bed of the reservoirs, though I haven’t attempted to calculate that. Finally, the new inland seas could supply new food sources.
The Sea Level has been higher in Portugal many centuries ago. It is well documented. Unfortunately, countries like the USA, which have much less history, tend to lack knowledge in this domain. As my history teacher told me long ago, you have to know some history so you can understand the present and predict the future!
[Response: I'm going to guess that this was either due to isostatic rebound from the removal of the European ice sheets after the last ice age or due to tectonic uplift. It was not a global signal. - gavin]
Further to 87 on Ref. 63, 73, 120…design levels for infrastructure
120 raises the issue for high risk structures such as nuclear power stations. Normally these are designed for increased actions (eg, often a maximum credible earthquake is used for design). Hence, it would be unaceptable to place such a structure in a floodable area.
Haveing read the Nature article (I cannot access the paper) I would revise my suggestions (87) to
For major infrastructure design or planning purposes
2050: 1.5m x factor of 2 = 3m
2100: 4m x factor of 3 = 12m
Critical infrastructure such as power plants or major highways should just not be located near the ocean unless it is acceptable to abandon them to the sea (if that eventuates).
Again revision would be required depending on the emergence of new information (tipping points, etc) and the degree of international effort to reduce emissions.
Am I being to pesimistic in the numbers? Comments please?
There’s a very small piece about (what appears to be) the Pfeffer et al Science paper in the Dutch newspaper “Volkskrant” (in the science section; it’s a quality newspaper and (I believe) regarded as slightly left leaning). It also mentions that sealevel will “only” rise by 2 meters at most by 2100, ie it refers to the estimate as a lowering compared to previous estimates.
On another note, and not surprisingly, the Dutch deltacommission is being attacked in Dutch media for using upper limits as their estimates of sealevel rise, even though the KNMI has been heavily involved and points out that the difference is explicable. In my reading, it has most to do with the higher estimate of the mechanically enhanced ice loss, to reflect the most current measurements and insights.
Mr. Levenson (#125), I agree completely concerning the rebuilding of New Orleans. Author Michael Tidwell “Bayou Farewell” said it best after Katrina in 2005. At a news conference his summation (as best as I can remember it) was “If you’re not going to rebuild the marshlands surrounding the city, don’t spend a dollar on rebuilding New Orleans, and if you’re not going to solve the global warming problem, don’t spend a dollar trying to rebuild the marshlands.”
This must extend much further than New Orleans however. The amount of wealth (capital) that will be destroyed by the rising seas worldwide is a number that no one has even come close to figuring to my knowledge. We can guess that the wealth destroyed by a two meter rise will be greater than that destroyed in all the wars in human history by a significant multiple. How will that wealth be replaced in a world struggling with a warming climate, rapidly shrinking glacial water supply, less readily available energy resources, changing agricultural patterns, encroaching coastlines, oceanic acidification, desertification, and the loss of biodiversity that supports our necessary ecosystems? In my uninformed opinion it cannot and will not be replaced in the foreseeable future, centuries, perhaps millenia.
We should be planning way beyond the 50 years planning regime mentioned in an earlier post, as even a coastal highway takes material resources and, at present, fossil fuel energy and waste products to construct. We will not get close to controlling our future until our mindset accepts these things and we begin to act accordingly. And as Hansen is so right to point out, at a certain point (which may be closer than we’ll presently acknowledge), nature will take us out of the decision with positive environmental feedback.
New Orleans and those other coastal cities that cannot withstand a 2 meter sea level rise (probably already in the pipeline during the next 150-200 years) should be slowly but steadily abandoned, starting today. Do we build or reconstruct a city for 50 years? Hopefully, much of the material resources (wealth, capital) in a condemned city’s structures can be recycled but that has to be planned too, before it is literally too late. After a Katrina, much, if not most, of the material is unusable rubbish.
Finally, if we are not going to immediately and significantly address global warming, we should be starting to look at those cities and areas that cannot withstand a 4 meter sea level rise.
Nigel, (#’s 22 & 123), your gorilla is just about too big to get our minds around. The question about what will stop the melting before 80 meters of SLR still stands as far as I know. What is the present scientific thought on this? Has anyone determined a sea level rise per temperature degree increase ratio that makes any sense and explains why it stops at any point before 80 meters?
This question must at some point be answered if humanity and a fair amount of the rest of the biosphere is going to have any long-term future. So we’re thinking several millenia here, that’s still a blink in geologic time. An effort to figure this out is not a lot to ask from the guilty party, before we finish committing the crime of knowingly carbonizing the atmosphere to the point of runaway global warming.
Thanks, the reason for my calling Rahmstorf et al. “spin” was this following statement that they made in their paper:
“Previous projections, as summarized by IPCC, have not exaggerated but may in some respects even have underestimated the change, in particular for sea level.”
This is untrue. The 1990 IPCC certainly made “projections” that have “exaggerated” sea level rise to date (I would use a different phrase that that used by Rahmstorf et al., probably “overstated to date”). To ignore the 1990 IPCC sea level rise projections (even if to explain them away as now irrelevant) when discussing “previous projections” is misleading at best.
[Response: Our paper compares the data to the scenarios of the IPCC Third Assessment Report, and nothing else. This is abundantly clear when you read it, and this is what we are discussing in the sentence that you call "untrue" above. We did not repeat the words "IPCC Third Assessment Report" in every single sentence, but refer in short to "IPCC", because we were not expecting people to maliciously pick sentences out of their context and deliberately misinterpret them so that they can call them "untrue". Stefan]
Mark (#126)- Stefan is the one who is worried about incomplete models, so your question is best put to him. My work simply compared “best estimates” with observations. All models are of course incomplete.
dhogaza (#127)- You are reading in too much — there is no pejorative intent. The IPCC’s 1990 “best estimates” are the IPCC’s “best estimates” from that time, and thus the basis for comparing with experience. All we can do is see how things have turned out. I am sure that 20 years from now we’ll look back on the AR4 as similarly simplistic. That is how science works.
Comment by Roger Pielke, Jr. — 7 Sep 2008 @ 12:08 PM
Question off topic:
Is Prof/Dr Ruddiman right about his GHG theory or humans preventing an ice age 10,000 – 5,000 years ago ?
Mike Tabony (131) — New Orleans and other gulf coast communities are already being slowly and steadily abandoned.
pete best (133) — The Holocene climatic optimum in central Greenland was about 7800 ybp. From orbital forcing and the behavior of the previous interglacials, one wouldd expect, on average, cooling since about then. Indeed, that has occurred, up to the present, defined as 1950 CE. W.F. Ruddiman is suggesting that without agriculture, it would be quite a bit cooler in the northrn hemisphere, but far from an ‘ice age’.
As I understand it, the next attempt at a stade (massive ice sheets) is due to start before another 20,000 years of, baring AGW, gradual cooling. For more information on this see David Archer’s “The Long Thaw” or also his papers linakable from his publications web page.
Why do the researchers set 80cm – the low end of their confidence interval – as a ‘default’ value? Surely it would be meaningful for them to give as a point estimate something like a maximum likelihood estimate? And for policymakers, surely the more important value is not the minimum the sea level could rise but rather the maximum that it is reasonably possible for the sea to reach?
Re #140, I believe that the IPCC would not speculate on unknown issues such as ice sheet melt due to the unknown nature of the threat posed, ie there is not enough good physics of ice sheet disintegration. Instead they concentrated on thermal expansion of the oceans and run off from rivers and possibly glaciers.
You have to page down quite a while to get past people quoting you and find
Journal of Climate Volume 15, Issue 20 (October 2002) pp. 2945–2952
Reasons for Larger Warming Projections in the IPCC Third Assessment Report
T. M. L. Wigley
“… In terms of total radiative forcing over 1990–2100, if TAR gas cycle and forcing science is used in both cases to isolate the effect of emissions differences, the net effect of these differences is that B1-IMA forcing exceeds IS92c by around 0.5 W m−2 while A1C-MI exceeds IS92e by more than 2 W m−2 (Table 2 ). Changes in aerosol forcing are the main reason for these differences in total forcing….”
Hi Mike #135! Kinda like we’re having a private conversation here.. how are the kids?!
Funny that in a thread with the title How Much Will Sea Levels Rise the entire discussion stops at the year 2100. Is that simply because most of the participants in the dialogue believe (hope!) they will be dead of old age by then?
To my mind (and the mind of every movie gangster) nothing focuses the mind more than the impending death of your grand children – of your own creations. Maybe that’s why the gorilla is so hard to deal with.
It must be (hey it IS) dispiriting for anybody involved in infrastructure (like for me involved in planning transport systems) to know that when my grand children look at most of my work they will say: “Why did he do this? He KNEW the sea was going to inundate this work! Why didn’t he build it someplace safe – like at 100 metres above sea level where we wouldn’t have had to re-build it?”
There are a number of reasons to focus on 2050 and 2100. First, these are basically the 50 and 100 year life times for structures. These numbers are used in many building codes and standards for the expected life of ‘normal’ structures and ‘important’ structures. Policy makers will use these for convenience.
Also, most of the projections relate to 2100 and it is expected that the projections will change over time as we gather more information. Thus we need an agreed time point to use as a measure.
I must agree though that the projected changes after that time have to be set out in the light of taking action to stop them.
If we don’t recognize the danger we cannot respond to it.
I will add to my last by including:
2200: 8m? x 4 = 32m ???
(Factor of 4 very difficult to settle on as there is so much uncertainty — what is the actual rate, are there tipping points, what can our race do to stop it or modify it once started, etc… should it be 5… or 6?)
This looks surprisingly like an approach towards the magical 80m doesn’t it! But remember, this is a risk based strategy for planning and would be used to locate difficult to replace infrastructure from a planning point of view.
In various articles, for instance, Hansen, James et al. 2007. “Climate Change and Trace Gases”, Philosophical Transactions of the Royal Society 365: 1925-54, and Hansen, James. 2007. “Climate Catastrophe”, New Scientist, 28 July: 30-34, James Hansen has been writing about the rise this century as being much larger. He even mentions it could be the better part of 5 metres by 2100.
I’m intrigued to know what you think of his rather grim forecast.
Hassling yourself over engineering a city for 1 meter versus 2 meters of sea level rise indicates that you are making a fundamental mistake. You shouldn’t have built a city that close to the water in the first place. In the present place, you should be moving the city, except for the harbor itself, to a new location at least 100 meters above sea level. You should be reversing the past culture of building in the valleys and leaving the hilltops natural. It is OK to cultivate the valleys, but the cities should be on the hilltops. Ancient history, when there were so few people and they had so little technology that we built a cabin next to the farm, no longer applies. My house is 600 feet above sea level in the heartland. I suggest you follow my example, or build new cities in the badlands at higher altitude.
There is no reason to put a nuclear power plant anywhere near sea level. De commissioning is not as difficult as somebody above suggests.
Reference: “The Long Summer” by Brian Fagan and “Collapse, How Societies Choose to Fail or Succeed” by Jared Diamond and Al Gore’s speech at the Democratic National Convention last month. Sea level rise is all moot anyway if civilization collapses in 30 years. Sea level rise will be only one aggravating factor in the collapse. Famine is the usual cause of the collapse of civilization. Only 1 person in 10,000 will survive, making planning for cities in 2050 pointless.
#116 Roger – I’m still struggling to see what your problem is. You say in your own article why comparing the 1990 figures is not like-for-like with the other years. So why include them in the Rahmstorf et al paper? To include them would have been misleading, surely, not the other way around? (and a layman’s shot, the reason why the paper made it happily through peer review.)
It seems that you agree with all the underlying points here, but still characterise the Rahmstorf paper as “spin”. I can well see that there is a case to be made that there should have been a reference to why 1990 was omitted, but – and this is the critical point – since those reasons are robust (and you agree with them it seems), it is surely unfair to call the paper “spin”. The authors do not attempt a feeble / inaccurate explanation, which would indeed have been spin, they simply omitted essentially irrelevant data, which is basic science.
I must confesss, I can well understand why Stefan does not read your blog when you throw allegations like “spin” around where it seems quite unfounded. You agree that anthropogenic climate change is real and its effects potentially extremely serious – surely it is beholden on you to not engage in this kind of misinformation in communication? By all means call for clarification and more research, but don’t stoop to unreasonable allegations – we can all ill-afford it.
Guy #150- None of the IPCC reports are “like with like” with each other in terms of methods, which evolve and change over time, so that concern is irrelevant. What is “like for like” is the fact that each IPCC provides “best estimates” for the future. I find that selecting among “best estimates” and presenting only half the story to be misleading, especially when the other half of the story suggests some very different conclusions.
Comment by Roger Pielke, Jr. — 8 Sep 2008 @ 8:20 AM
Is it possible that the higher surface temperatures north of Siberia and Alaska are due to methane being released from hydrates in the sea shelf, creating a more intense local greenhouse effect?
[Response: very unlikely. Remember that most of the impact from greenhouse gases globally occurs because of feedbacks - and those are often non-local. For instance, water vapour changes in these regions are less affected by local changes in temperature than they are by conditions over the upstream oceans. -gavin]
“Shakhova and her colleagues gathered evidence for the loss of rigor in the frozen sea floor in a measuring campaign during the Siberian summer. The seawater proved to be ‘highly oversaturated with solute methane,’ reports Shakhova. In the air over the sea, greenhouse-gas content was measured in some places at five times normal values. ‘In helicopter flights over the delta of the Lena River, higher methane concentrations have been measured at altitudes as high as 1,800 meters,’ she says.”
“You shouldn’t have built a city that close to the water in the first place. In the present place, you should be moving the city, except for the harbor itself, to a new location at least 100 meters above sea level.”
Well said. This cannot be over emphasized. Rising seas is not the only peril along a coast. We all love to look at the blue water, I get that but there are unstoppable forces in nature like the long shore current, to name one, even if sea level weren’t rising, which it is.
#152 – but hold on, you concede that 2007 is quantitively different, and yet you also concede the reasons why 1990 is quantatively different. Sure the science is always advancing, but 1990 left out aerosols completely, and 2007 left out dynamic ice-sheet processes – both of which are quite different and should not be compared like-for-like with 1996 or 2001, which attempt to be all-encompasing (please someone put me right if I have this wrong!!!)
But I seem to have made this point several times, and Stefan has answered too (btw, I don’t think you’ve responded to his inline of #136, which is new). You’ll forgive me, but I have to conclude that you have some sort of agenda here by not simply supporting the good (and uncontentious) work of other scientists and accusing them of some form of deception. Perhaps in the interests of greater understanding it would help us all if you would elaborate as to what this agenda is?!
Overselling or misrepresenting science is not good no matter who does it. My original response to this thread makes this same point in the context of the claim that “no-one (and we mean no-one) has published an informed estimate of more than 2 meters of sea level rise by 2100″. This is just wrong.
Here is what Jim Hansen said:
“As an example, let us say that ice sheet melting adds 1 centimetre to sea level for the decade 2005 to 2015, and that this doubles each decade until the West Antarctic ice sheet is largely depleted. This would yield a rise in sea level of more than 5 metres by 2095.
When science is oversold you will indeed get news stories that say that a prediction of 2 meters is a reduction. Sorry, but it just can’t have be both ways.
Similarly, Stefan (#136, thanks for the pointer) says that his take-away line from his article on evaluating IPCC projections was imprecise, saving the effort of adding “TAR” to that last sentence, sorry, nothing personal or malicious, but I find that very misleading.
You are of course free to disagree ;-) And if you are interested in my “agenda” on climate policy or science policy, feel free to visit our site, where you’ll find more on that than you would want.
[Response: Roger, are you criticising Jim Hansen or are you criticising us? Your quote of Jim's speculation seems to imply that him saying this is the definition of the 'science being oversold' - I do not accept that characterization of his thought experiment but neither do I think that this counts as an 'informed estimate' - no ice sheet data or modeling was used, and his statement later on in the same paper as well as this one makes it clear that this is only very loosely constrained speculation. If the mere fact of Jim publishing his thoughts on the matter is 'overselling the science', presumably you think he should have been prevented from doing so? But if prior restraint on Jim is not what you propose (and that has a bad track record of effectiveness), then it must be that someone else is guilty of this overselling - who might that be? and what do you think they should have done instead? - gavin]
Comment by Roger Pielke, Jr. — 8 Sep 2008 @ 10:33 AM
The terms of the law authorizing construction actually require a 99.9999% probability of surviving a 200-year return event. The project is near sea level, so floods and levee breaches are included as events the facilities must survive. In this vein, I would strongly endorse requiring all of the California legislators and members of the US Congress to take an extended course in statistics. Because of the language in the law, the PE is under some stress with respect to bonding and liability.
How many standard deviations is the current Arctic Sea Ice condition from say the 1979-2000 baseline? (Six, you say? We have a one- in a million event.) We are already in a long tail event. I can hear E. Deming saying, ”The system is in not in control. You have not looked at all of your data, and you have not thought through the implications of the data and observations that you have looked at. You have not done the math. You have not told the truth.”
Read Deming and tell me the system (Earth) is in control. Tell me you have absolute confidence in the quality of the data going into the GCM. Tell me that the precision and confidence of that data is known, and carried through all calculations. Tell me that nothing has been left out of the GCM (such as dynamics of ice sheets.) Tell me that feedbacks such as CO2 release from permafrost and clathrates have been fully accounted. Tell me that ocean currents are well calculated and reorganizations of ocean currents will be calculated as they occur. Tell me we understand in detail how an open Arctic Ocean will affect rain on the GIS. Tell me that we understand how a warming southern ocean will affect the base of the WAIS. Tell me that climate guys with the most accurate predictions in get the most pay, and there is no premium for downplaying the dangers of global warming.
By the standards of data quality established by the US EPA for CERCLA, the data quality in climate science is poor. (I helped write some of the early drafts of ASQC-E4 and the ASTM data standards for human health risk assement.) And, yet the risks to humans from global warming is at least as great as the risks form releases of toxic materials Our risk assement data for impacts from global warming should be as good as our risk assement data for toxic releases.
Current GCM do not include behavior of ice sheets, and thereby cannot be used to estimate the impacts of global warming. Sea level rise impacts melting of permafrost (release of CO2), availability of resources (i.e., stock exchanges), availability of fuel, organic chemicals, fibers, and fertilizer, transportation. The issues that bother me most is the failure to consider loss of food production resources (fertilizer/fuel) as sea level rises. Lack of food due to lack of fertilizer/fuel would shut this place down real fast Any analysis that does not fully consider these issues is incomplete.
Until we have good quality data and all factors are included in the calculation of the impacts of global warming, then guesses about sea level rise from ice dynamics are not better planning tools than the IPCC estimate of sea level rise from thermal expansion. Such guesses are not a basis for prudent planning. Moreover, any such guesses that do not include all known factors inspire false confidence. Hence, my desire for a maximum plausible SLR value that includes all factors and data
Roger, I find it fascinating to see you lecturing scientists about how science works. Your misrepresentation of Stefan’s words is simply a case of pulling something out of context, then trying to whip it up into a controversy about the credibility of scientists. Your words are perjorative, and unfairly so. There is simply no justification for your use of the word “spin” in the way you have.
Ps — Aaron, I’m sure whatever law you’re talking about is by its terms referring to prior 200-year event experience. They weren’t requiring accuracy in 200-year forecasting of weather at that location.
Mr. Aaron Lewis has spoken of rainfall in Greenland weakening the ice sheets. I have seen measurements and estimates of annual precipitation in Greenland, but I do not recall any that separated out rain as opposed to snow. I would appreciate pointers. I would also expect rain to cause a drop in the surface height, and rain on the flanks should steepen the surface slope.
Now that we have many lasers and such, has anyone undertaken careful altimetric studies before and after a rainstorm in Greenland ?
Aaron Lewis (156) wrote “The terms of the law authorizing construction actually require a 99.9999% probability of surviving a 200-year return event.” COuld you kindly explain more fully. The law where? Are these (essentiaaly) the same terms throughout the developed world?
I read THE RISING-JOURNEYS IN THE WAKE OF GLOBAL WARMING, a novel (see http://www.risingglobalwarming.com/ ). One of the points they make is a few feet of sea rise is enough to cripple California’s water system — and CA can’t really afford that with diminishing potable and ag water from GW & other causes.
Their scenario is interesting. In addition to AGW increasing the sea level, some really dangerous types of volcanoes under the Antarctic erupt and melt a lot of ice pronto, which raises the sea a lot in a much shorter time. It’s farfetched, but how close the CA water system is to sea level is real, and pretty scary….I suppose someone it working on some dikes over there.
A fair percentage of the comments here are stating we can expect sea levels to rise by a minimum of 2 metres by 2100. This seems to be based on the idea of a vastly increased global ice melt. Nearly all of the examples of melt seem to involve the NH only, why?
90% of the global ice is contained in the SH so why is there hardly mention of it? A 5% increase in SH ice is equal to 50% of total NH ice after all.
I would hope that this lack of discussion in SH ice, which after all is the overwhelming factoe in any sea level rise based on ice melt, is not due to the fact there is no evidence of decreasing ice levels in the SH. Indeed Antarctica, which contains most of the worlds ice, has been geting colder for some time now with evidence of increasing ice levels.
For these, what could almost be called alarmist, sea rise levels mentioned here to come to pass, the average sea level rise needs to be 20mm per year for the whole of the 21st century. Where is the evidence that this is a probability? Sea level rises shows no sign of the huge acceleration that would be required to get anywhere near this. Indeed it is quite the opposite at the moment, unusually we seem to have had no rise at all in sea levels for the last 3 years or so!
The other current indicators do not seem to support any such speculations. Sea temperatures have shown a slight cooling over the last few years. Global temperatures have stalled since 2001 with a slight cooling in fact.
Basing everything on computer models which are slowly moving away from actual Earth conditions does not seem to be ‘proper’ science to me.
I actually don’t seem to see much effort being put into trying to explain and calculate the reasons and factors which seem to have stopped the, hypothesised, inexorable rise in global temperatures caused by Mankinds CO2 emissions. Emissions which have continued to increase post the models.
I would hope that this is not because any proven results would completely undermine the whole AGW theory, which is based on the theory that CO2 was the ‘last man standing’ when all other natural factors were eliminated because of their calculated maximum effect.
I suppose the idea out there is that, if a combination of natural factors could produce that amount of cooling then, it is just as likely that a similar combination of factors could cause a similar amount of warming. Something that the hypothesis of AGW can not allow.
The pumps which lift the water from the Sacramento/San Joaquin rivers are just about at current sea level in the Delta. And there are dikes around the islands in the Delta, since some of the farmland is now 25 feet (7.6 meters) below current sea level due to the erosion of peat soil.
The transport of fresh water to Southern California is part of the reason our governator is reviving the plan to build the “Peripheral Canal” to route water around the Delta. But as I keep pointing out to the engineers, the old Peripheral Canal was designed without sea level rise in mind. One of Schwarzenegger’s task forces is urging him to prepare for a sea level rise of 55 inches (1.4 meters) by the end of this century.
In its report to the governor, the task force surveyed 23 state and federal agencies to learn their sea-level predictions. Only two, both closely associated with the task force itself, have considered a potential rise of 55 inches. Those are the CalFed Bay-Delta Program and the Delta Risk Management Strategy, a research effort by the Department of Water Resources.
Other estimates for 2100 fall between 28 and 35 inches. But 11 agencies have no estimate to guide their work, Delta Vision found, including Caltrans, the U.S. Army Corps of Engineers and Bureau of Reclamation, the state Public Utilities Commission and Water Resources Control Board.
I am not criticizing Hansen, he is free to issue whatever prediction he wants. Back on point, the Colorado press release said nothing about “informed estimates”, that was your invention. It simply said:
“Despite projections by some scientists of global seas rising by 20 feet or more by the end of this century as a result of warming, a new University of Colorado at Boulder study concludes that global sea rise of much more than 6 feet is a near physical impossibility.”
I think that it has been pretty clearly established that “some scientists” have made such “projections,” whether they are “loosely constrained speculation” or whatever you wish to call them is irrelevant.
You claim that “The problem is not that people think that we will get 6 meters of sea level rise this century . . .”, well it is a problem if you want people to view 0.8 or 2 meters as a large number, because once there have been uncontested worldwide headlines about 5 meters (or even 25 meters!) this century, 2 meters just isn’t newsy, and indeed looks like a big step back.
In this context, complaining about completely accurate press releases approved by your colleagues as “spin” or labeling entirely appropriate media interpretations as misleading just isn’t productive. That happens to be my opinion, I respect that you see things differently.
We’ve aired our different points of view for all to see, and you can have the last words on this exchange if you’d like ;-)
[Response: I think you are failing to see the wood for the trees here. On any issue I can find someone, somewhere who has said something that my latest results are smaller or greater than. If my model says rainfall will increase 3%/deg C, then I can claim it's much less than some scientists have said, or much more than others. Either way my statement will be accurate, but the framing will impart spin to the result and lead to completely opposite headlines "Rainfall to raise faster than expected" or "Rainfall raise not as bad as expected" - since both things cannot be true, one must perforce be misleading. Which depends on the context of what is 'expected'. The implication is that it is a general expectation, not just what one person thinks. General expectations in the climate community have been usefully written down, reviewed, critiqued and summarised in assessment reports like the IPCC, the NRC or the CCSP reports.
We chose the words in the above post quite carefully, because there is a big difference between someone saying something speculatively and something being generally expected. Whatever the merits of Jim's statements, you cannot claim that they are the consensus - that was after all the point he was making in the ERL paper. As to "uncontested worldwide headlines" claiming 5 or 25 m sea level rises by 2100, you are flat wrong. Headlines, yes. Uncontested? No - and I provided examples of that contestation above (but even I am hard pressed to find a headline claiming 25m - citation?).
By framing their result as a contrast to Hansen's perceived views instead of the IPCC report, Pfeffer et al opted for a public airing of a argument that only a small number of scientists would 'get', instead of making a statement that would educate the much larger number of people who had heard about or read the IPCC report which clearly stands as the most recent community statement on this topic. That is a lost opportunity. Whether critiquing media reports is productive depends very much on whether the community learns to do better - personally I think they can - in particular by taking note of the wider context in which their news will appear. - gavin]
Comment by Roger Pielke, Jr. — 8 Sep 2008 @ 8:53 PM
The problem with the large sized rise in sea level is there is no time frame attached. Gore does it, Greenpease does it (and is being sued in Spain). Here is an example:
“James Hanson, a NASA Scientist, has demonstrated that warming above 1.5 -1.7 degrees is likely to cause the melting of both the West Antarctic and Greenland Ice Sheets. If these enormous blocks of ice melt, global sea level would rise by 25metres, flooding major cities and river deltas – the world would be a very different place. To prevent this warming will require reductions of at least 100% by 2030.”
People get the distinct impression this is soon, 100 years at most. What people do not understand is it would take at least a 1000 years for Hansen’s prediction to come true and produce that much increase. Thus without giving a time frame with the predictions is grossly misleading. At least now with this paper we have an upper limit proposed by 2100. So now the big radical predictions will have to be in perspective.
Besides, in 1000 years it won’t matter. There will be far fewer people on the planet, cities will be largely abandoned, because we will have consumed the last of the available fossile fuels 900 years before.
Comment by Richard Wakefield — 8 Sep 2008 @ 9:19 PM
Here is another series of misrepresentations from the Bali conference last year:
Jakarta airport to be under water by 2035. (the airport is 21 feet above sea level)
about 25% of Jakarta will vanish by 2050.
Surabaya and Semarang will be almost permanently flooded by 2080.
the capital will have to be moved to Bandung.
2,000 islands will be lost by 2030.
400,000 sq km of land mass lost by 2080, including about 10% of Papua, and 5% of both Java and Sumatra (on the north coast).
Says Nicholas Stern, author of the Stern Report on climate change (2006):
[Response: The only source of sea level figures in that post is the 18 to 59 cm in the IPCC report. But those statements appear to have come from an Indonesian meteorologist Armi Susandi, apparently based on a 50 cm rise. Neither of those figures are alarmist. But whether those headlines are wrong or not depends on where they come from and how they were calculated. I'm not in a position to tell. Find a real citation and we can talk. - gavin]
Comment by Richard Wakefield — 8 Sep 2008 @ 9:26 PM
GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L01602, doi:10.1029/2006GL028492, 2007
On the decadal rates of sea level change during the twentieth century
S. J. Holgate
Proudman Oceanographic Laboratory, Liverpool, UK
Nine long and nearly continuous sea level records were chosen from around the world to explore rates of change in sea level for 1904–2003. These records were found to capture the variability found in a larger number of stations over the last half century studied previously. Extending the sea level record back over the entire century suggests that the high variability in the rates of sea level change observed over the past 20 years were not particularly unusual. The rate of sea level change was found to be larger in the early part of last century (2.03 ± 0.35 mm/yr 1904–1953), in comparison with the latter part (1.45 ± 0.34 mm/yr 1954–2003). The highest decadal rate of rise occurred in the decade centred on 1980 (5.31 mm/yr) with the lowest rate of rise occurring in the decade centred on 1964 (−1.49 mm/yr). Over the entire century the mean rate of change was 1.74 ± 0.16 mm/yr.
BTW, half the CAPTCHA text is unreadable most of the time. And the sound is garbled.
[Response: Current rates are about 3.2 mm/yr, long term rates over the last century or so are more like 1 to 2 mm/yr. This implies an acceleration- whether or not it is sustained remains to be seen. - gavin]
Comment by Richard Wakefield — 8 Sep 2008 @ 9:45 PM
What people do not understand is it would take at least a 1000 years for Hansen’s prediction to come true and produce that much increase.
You can’t possibly expect anyone to take you seriously.
Gavin (156), your point on Hansen’s comments make a good logical point; but it’s not perfect. An ad hoc “official” climate statesman, and probably the poster boy for climatology testimony has zero business going around musing and speculating.
[Response: I completely disagree. People need to speculate and muse and have their ideas be tested no matter who they are. These kinds of discussion both provoke interest and focus attention on uncertainties that are not being addressed. Non-linear responses of ice sheets to models is a topic that clearly needs more attention and research. - gavin]
“A fair percentage of the comments here are stating we can expect sea levels to rise by a minimum of 2 metres by 2100.”
I don’t know which comments you refer to, but 2 meters by 2100 is generally seen as a high estimate, not a minimum.
“This seems to be based on the idea of a vastly increased global ice melt. Nearly all of the examples of melt seem to involve the NH only, why?”
Because the NH warms faster and the Greenland ice sheet is a lot closer to the equator than antartica.
“Indeed Antarctica, which contains most of the worlds ice, has been geting colder for some time now with evidence of increasing ice levels.”
Could you please provide us with a data source where the increase in ice levels is shown?
Hopefully it was not your intention, but you may have given given people here the impression that Stern was the author of those dire predictions in your post.
These words you took from the “Indonesia Matters” web site…
“Says Nicholas Stern, author of the Stern Report on climate change (2006):”
…do not refer to those predictions preceding them in your post.
It refers to another quite unremarkable comment attributed to Stern (“Island states are very vulnerable to sea level rise and very vulnerable to storms. Indonesia is particularly vulnerable.”) in the site to which you linked.
Roger’s inability to answer the spin problem (#156) is revealing. Clearly there is nothing more to be gained by going on and on about it, but choosing to deflect one failed debate onto another – James Hansen – is indicative that we have moved beyond the realms of science, and onto another agenda entirely (whatever that may be). And coming from a senior climatologist, that is science’s loss.
Speaking of James Hansen, clearly James’ views represent the upper band of what is likely among climate scientists. However, given current the universally unpredicted real-world pace of sea ice decline, his words seem less those of an alarmist for focusing at the upper end, but of a realist. It also seems to me that although this current paper has helped move the debate on, it cannot represent a complete understanding about what could be at stake, given the speed of previous geological events (but happily willing to be shown the error of my ways on that). Further, even this could be a moot point – if, as Hansen (and others) suggest that soon we will pass the point at which we have any ability to slow the rate of change, ethically it doesn’t matter if catastrophic change takes place in 20 years or 2,000 years – it is past generations and especially this one that have lit the inextinguishable fuse, and therefore bear full responsibility.
Which leads to one particularly awkward and inescapable conclusion. Why does James Hansen appear to be alone in his current sense of political urgency? Of course the IPCC has made a very powerful consensus statement, but if Hansen is correct that a target of 2 degrees warming represents climactic suicide, and we have mere months to persuade world governments of drastic action, why is he appearing to be receiving so little practical support from his colleagues? Waiting until the next IPCC report will be too late. Perhaps it is time for a new consensus statement from the world’s leading climate scientists, aimed specifically at urgent political action (a la Hansen) based entirely on science? Are you all really doing *everything* that you can? Would be grateful for the thoughts of Gavin or Stefan on this….
Thanks for your posts David, they are very informative. Are you working in climate change or just an interested observer like me?
Does this 3 C relate to local (Antarctic temperature or estimated global temp?
If the peak of the Eemian was 3 C above today, then in my mind it is probably the most useful guide to what we can expect in terms of sea level rise. The 20 foot rise constrains what we can expect of a 3 C rise to under 6 metres. Presumably during the Eemian peak there was time for “fast response” processes to reach equilibrium (ocean temperature, ice etc.), although not perhaps some slow responses. The Eemian was a similar world to todays. The same ice sheets. Similar geography and sea level. One key difference was the CO2 level.
More detaled kinetics of sea level and temperature at this time would be informative. How accurately are sea levels known and how well can they be aligned with temperatures?
Sea level rise is just one of the negative Forcings on human activity. We have three big ones currently running.
The longest-term is sea level rise – If everything else was not running against us then coping with sea rise would entail the highest level of survival-focussed human activity ever seen – the relocation and reconstruction of about half of all humanity and its essential infrastructure. Let’s say that forcing is 50% upon us in 500 years.
The mid-term threat is climate change on agriculture and infrastructure (Haiti after Gustav and Ike are extreme instance; Spain, Australia’s Murray Darling Basin and the USA South are other examples). Say these effects (drought, flood, storm, fire and the odd case of pestilence and brimstone) will be hitting us at 50%strength in maybe 50-60 years.
The immediate threat is peak energy. 50% into that within 20 years – probably 10, maybe less.
Now each of these forcings will roll us in different ways, and with different intensities and with regionally-specific impacts and senses. It’s a very hard sum to do.
But the trick for us is the sweet way these are sequenced. To cope with climate change we need the energy we won’t have. To let us cope with sea level rise we need the energy and the kindly climate we won’t have.
So if we want to arrive anywhere sensible in the long term, then we need to go for broke starting yesterday. (Lovelock identified the cusp as being around 1965). We need to grab what ever resources and hence what ever source of energy we need right now (coal – who cares) to build the sea-level-rise-life-boat within the time we have. That life boat will include critical food supplies in climate-proof shelters to let us at least survive climate change high and dry.
But if we don’t act now we will use our energy on trips to the movies, and we won’t have any way to produce essentials in the face of climate change, and without that we won’t usefully manage (indeed most won’t survive) the retreat from the coast.
So how do we get that message across? If we don’t our future generations will be in deep trouble. Humans don’t recognise distant threats too well, so maybe we need to focus on addressing the nearer-term threats first. That’s the way they are being presented to us, and that is the ‘correct’ sequence in which to address these threats. Let’s all go out and scream about energy supply-demand divergence and yell about climate change impacts on where we each live. Local action. If we get that right then we will stand a chance when the dykes are over-topped.
Gavin, you are missing the point. The point is this dire prediction from Bali was all over the news, I remember see it many times when they reported on the conference. The point is NO ONE from the AGW community went public to denounce those numbers are wild speculation. Hence the public at large gets the impression that you people agree with thse dire predictions. Thus you are all complacent with these unscientific dire alarmist predictions.
[Response: Not at all. I have never seen those claims before, and if someone had brought them up here I would have questioned them (but actually since you still haven't shown me the source, I have no idea whether they are valid or not - there are an awful lot of islands in Indonesia). There are scores of examples where we have countered exaggerations (sea level, climate sensitivity etc) and you only need to spend a small amount of time here to see that. Your claim that "NO ONE" does this is specious. I am neither complacent, nor complicit, with 'alarmist' predictions. - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 8:23 AM
Try this: put one ice cube in an empty glass, another in a glass full of water. You’ll see the second melt completely long before the first. As an amateur I don’t know about the fine points here, but essentially, other things being equal, the water is a much more efficient “heat donor.” Of course, you can change the ability of the air, too–by using a fan to blow a *stream* of air across the first ice cube, for instance.
Another point is that glaciers don’t stay “where they are” anyway–they are dynamic systems, so all those interacting factors–glacial flow, precipitation scenarios, radiative forcings, atmospheric conditions–would need to be considered to make predictions.
Gavin has let the cat out of the bag. His link to the long term trend in sea level shows no acceleration, but a constant rate of increase. Published papers show there is a decadal fluctuation in the rate of sea level rise, and the current rate has not broken through that variation. Thus the current rate cannot be attributed to AGW. Plus, there is a serious logical problem with linking this rate to anthropic global warming. CO2 emissions over the same period has not been linear, but in fact follows a classic growth curve.
From 1850 to 1945, when we experienced a large proportion of the warming, our emission level went to 1200 MMTC/Yr, a mere 14% of today’s level. From 1945 onward we saw an 8 TIMES increase in CO2 emissions which comprises 86% of the total increase since 1850. Yet half that time, 1945 to 1975, the planet cooled right when the rate of CO2 emissions increased 4 TIMES. Half of the increase in CO2 has been in the last 40 years, the last 10 of which the planet has not warmed in spite of a 20% increase in CO2 emissions.
Since sea level rise has not changed its’ rate over this entire period one has to question if any of the current rate has anything to do with AGW. If there were a correlation one would have expected to see some sort of “hockey stick” in the rate of sea level rise. But it’s not there.
This has serious consequences for AGW theory
[Response: Again, no. Sea level rise so far is associated with the very slow (but persistent) take up of heat by the oceans (which if you hadn't noticed is a big place). The amount of SLR in recent decades fits very nicely with the expectations of models, measurements of ocean temperature change and estimates of ice sheet melt. The increase in the future due to thermal expansion will see a relatively slow growth, but the changes from the ice sheets is increasing much faster. Your imagined 'expectation' coincides with no 'expectation' that I have ever seen. Read the IPCC report (section 10.6) to inform yourself about what people actually expect. - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 8:49 AM
Gavin, how come no one at Bali came out and corrected these wild predictions at that time then? That’s the problem. It got into the MSM and was disseminated around the world. I waited to hear any rebuttal to these from anyone, and nothing appeared in the MSM. Thus the public thinks this is the consensus! Major damage is being done to science because of these wild unscientific alarmist predictions. What you and Hansen need to do to correct this is hold a news conference with the MSM and make it clear to the PUBLIC, not your readers of RC, what the actual scientific position is. You have a problem with doing that?
I posted the links of the source.
[Response: I have no idea what people did at Bali. I wasn't there. Your source is a third hand blog post and its insinuation that these numbers came from Stern is simply wrong. Something so specific must have come from a regional, likely Indonesian, assessment and you insist that they are wrong but with no source or cite to show that to be the case. If those claims are based on the sea level rises quoted in your 'source' then they aren't wrong. I give public talks all the time and have a book coming out on the same topic. I hardly think you can accuse me of being shy. - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 8:56 AM
Thomas Lee Elifritz Says:
8 September 2008 at 10:00 PM
What people do not understand is it would take at least a 1000 years for Hansen’s prediction to come true and produce that much increase.
You can’t possibly expect anyone to take you seriously.
Then enlighten us as to your cacluations to show it would be sooner. According to Pfeffer et al such a rise would take at least 2500 years.
[Response: Not so. You cannot extrapolate linearly - many of their assumptions will break down long before then. - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 9:00 AM
Alan, I’ve put some of your words in quotes & responded point by point.
“I would hope that this lack of discussion in SH ice, which after all is the overwhelming factoe in any sea level rise based on ice melt, is not due to the fact there is no evidence of decreasing ice levels in the SH. Indeed Antarctica, which contains most of the worlds ice, has been geting colder for some time now with evidence of increasing ice levels.”
*National Snow and Ice Data Center shows a decreasing trend for ice *globally.* Moreover, the picture in Antarctica is quite mixed–the peninsula has been warming quite rapidly and has exhibited some very dramatic ice loss.
“The other current indicators do not seem to support any such speculations. Sea temperatures have shown a slight cooling over the last few years. Global temperatures have stalled since 2001 with a slight cooling in fact.”
*You hear this from denialist sources a lot. But trends are not calculated by point-to-point comparisons; you have to consider the shape of the plotted data curve as a whole, and for a sufficiently long period of time. (That said, I don’t understand why you pick 2001, given that 2005 was the warmest on record in some datasets–if you are going to cherry-pick, go for 2005 at least!) The computed global merged land-sea trend is, if I remember correctly, currently at .17 degrees warming per decade.
“Basing everything on computer models which are slowly moving away from actual Earth conditions does not seem to be ‘proper’ science to me.”
*Explore this site to learn about the other lines of physical evidence–it is far from just model-based. It is interesting, and, to me at least, quite eye-opening.
“I actually don’t seem to see much effort being put into trying to explain and calculate the reasons and factors which seem to have stopped the, hypothesised, inexorable rise in global temperatures caused by Mankinds CO2 emissions. Emissions which have continued to increase post the models.”
*That’s because your premise–the “seem to have stopped” part–is just wrong. See above, or check out the 2007 climate report at the National Climate Data Center site.
“. . .the whole AGW theory. . . is based on the theory that CO2 was the ‘last man standing’ when all other natural factors were eliminated because of their calculated maximum effect.”
*Again, explore this site to find out why this statement is not really correct. AGW theory is fundamentally based upon firmly-validated physics that show CO2 (and other GHGs as well) do in fact have characteristics enabling them to “force” the climate. The checking of other explanatory factors which you reference is the obvious (and scientifically responsible) next step–and it has been carried out to the general satisfaction of the climate science community–even skeptics like Professors Spencer and Lindzen agree with the theory to this point. (They are essentially postulating that water vapor feedbacks occurring through some as-yet undiscovered mechanism will somehow save our collective butt. Their position, paraphrased, is “AGW is real, & is happening, but won’t be so bad.”)
“I suppose the idea out there is that, if a combination of natural factors could produce that amount of cooling then, it is just as likely that a similar combination of factors could cause a similar amount of warming. Something that the hypothesis of AGW can not allow.”
*If you are saying that AGW theory presumes that natural variability is unimportant, then you are wrong. Natural variability–AKA “noise,” as contrasted with a climate “signal”–continues and nobody disputes this. Natural variability is in fact exactly what make trends hard to spot, and crucial to measure correctly. When you claim a “cooling trend” based on point-to-point comparison, I am afraid it is you who is failing to take adequate account of this natural variability.
Hope this helps. Please do read the explanations found elsewhere on this site. Spencer Weart’s “Discovery of Global Warming” is also an excellent account, and deals very clearly with many of these points; you can access it from this site, and Dr. Weart has in fact just done a very nice RealClimate guest commentary on the inherent complexity of numerical prediction in climate study.
Gavin, so you are agreeing then that from 1850-1945 the amount of CO2 could not affect the rate of sea level. Since that rate has not changed except decadal variation since 1850 then the current rate of sea level cannot be from AGW? It’s a logical consequence.
“At best, the determination and attribution of global mean sea level change lies at the very edge of knowledge and technology. The most urgent job would appear to be the accurate determination of the smallest temperature and salinity changes that can be determined with statistical significance, given the realities of both the observation base and modeling approximations. Both systematic and random errors are of concern, the former particularly, because of the changes in technology and sampling methods over the many decades, the latter from the very great spatial and temporal variability implied by Figs. 2, 6, 8. It remains possible that the data base is insufficient to compute mean sea level trends with the accuracy necessary to discuss the impact of global warming–as disappointing as this conclusion may be.”
This begs an important question for you. How many more years of no acceleration will it take to abandon AGW theory?
[Response: But I said nothing of the sort. CO2 (and other GHGs) increases up to 1945 are a significant forcing but not substantially larger than other forcings on a decadal time scale (solar, volcanic etc.). The GHG signal only starts to be dominant by around 1980, but that isn't the same as saying it had no effect before. However, your assessment of the solidity of the decadal SLR trends prior to the satellite trends is more confident than is warranted. Attribution of the latest 30 years or so is possible - before that we don't have enough data on ocean temperatures or ice sheets to do it. (PS. AGW is based on the radiative impact of CO2 and other atmospheric constituents - none of those things depend on sea level rise. PPS. Look up what 'beg the question' means.) - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 9:05 AM
Or are already breaking down. Again I ask, how many years will it take to melt all the ice and produce Hansen’s prediction? There must be some sort of physical limit. Show us why my 1000 year prediction is incorrect. It is imperative in science to be clear. Hansen el al making such large claims with out some sort of time reference is irresponsible and highly unscientific.
[Response: No. Collapsing ice sheets have lead to SLR of meters per century in the past (MWP 1A, or even the early Holocene final collapse of the Laurentide). We know that 4-6 meters of sea level are consistent with a further warming of the poles of 3 to 5 deg C (compare to the Eemian). Collapse of the WAIS is not a fiction. It has happened before. But though no-one can say how fast it happened, does not mean that it is highly irresponsible to discuss it. That discussion is motivating a great deal of work (including Pfeffer et al, but also Rignot, Payne, and many others) to be more quantitative. The science is not yet done, and yet you are convinced that it can't happen. Based on what? - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 9:10 AM
Gavin (176), you have a valid point (again). Whether musing and speculating is helpful or not entirely depends on the audience; and, I agree, with the correct audience, it’s not only O.K., it’s highly desirable.
Richard Wakefield enquires: “This begs an important question for you. How many more years of no acceleration will it take to abandon AGW theory?”
Sigh. Yet another denialist who thinks philosophy of science began and ended with Popper. Richard, how about if we just say that we will embrace a new theory just as soon as somebody comes up with it and it turns out to explain the data–all of it, produced by over 150 years of climate–better than the current one. That’s how science works. It is extremely unlikely that said theory will look a whole lot different than the current one, but you or anyone else is free to try and develop one. Go ahead. We’ll wait.
Bruce Tabor (181) — I’m an amateur student of climatology.
The 3 K was what was measured in the Vostok ice core. The northern Greenland NGIUSP ice core gives 5 K increase over present in the Eemian. The IPCC AR4 shows a modeling of the Greenland ice sheeet during the Eemian, much reduced.
Due to isostatic rebound it is currently not possible to state what the sea highstand was with precision; 4–6 meters depending upon just where one looks; I know nothing about the ‘alignment of temperature’, but opine that it would lag somewhat.
Due the peak of the Eemian in Antarctica, the CO2 concentration was 287.1 ppm according to Petit et al. Dr. James Hansen has suggested that at today’s elevated CO2 concentration that Antactic ice sheets are at serious risk; you can obtain copies of his papers on his web site.
The ice core data comes from the NOAA paleoclimatology web site; accessible to all.
“The GHG signal only starts to be dominant by around 1980, but that isn’t the same as saying it had no effect before.” Provide peer reviewed evidence it did prior to 1980 and by how much.
[Response: Tyndall (1863). - gavin]
“However, your assessment of the solidity of the decadal SLR trends prior to the satellite trends is more confident than is warranted. ” Then publish a paper refuting Holgate, until you do you are only speculating which hence can be rejected.
“Attribution of the latest 30 years or so is possible – before that we don’t have enough data on ocean temperatures or ice sheets to do it.” So your are claiming that in situ measurements from the last 110 years, such as
are wrong? Only satellite data can be trusted to be correct? LOL!! That’s funny. There is no acceleration in any in situ measuerments. Satelite measuruments are way too short and not reliable. That’s what’s in the peer reviewed papers!
” It is difficult to detect the geographic “fingerprint” of long-term climate change signals using altimeter data from a single satellite mission such as T/P, because the mission length will probably be insufficient to easily differentiate these signals from interannual and decadal variations.”
“Figure 2 shows variations in global mean sea level observed over the first 8 years of the T/P mission [Nerem et al., 1999]. The 15-20 mm rise, and subsequent fall, of mean sea level during the 1997-1998 ENSO event was interesting in itself, but also somewhat dissappointing since it will require us to have a much longer time series of altimeter measurements in order to average through the ENSO events and detect the true long term change.”
Fact is, if the rate of sea level does not change AGW is in deep trouble. Melting ice is everything to the theory.
[edit - keep it calm]
“We know that 4-6 meters of sea level are consistent with a further warming of the poles of 3 to 5 deg C” That’s an assumption and no evidence to support that this will actually happen. It’s a prediction from models only.
[Response: No. It's what you get from looking at the Eemian. No models necessary. - gavin]
“Collapse of the WAIS is not a fiction. It has happened before. But though no-one can say how fast it happened, does not mean that it is highly irresponsible to discuss it. ” It most definitely is if you do not give a time frame and leave in the public mind that it will be sooner than you know or suspect. That’s tantamount to deliberate misrepresentation. So give us a time frame! If you cannot even give some ball park realistic time frame then you should not be saying anything, period!
You do realize that by allowing continued misrepresentation you will be subject to two things.
1) once the real evidence comes forth, you will look like fools. That I really do not care about. But what I do care about is…
2) once the real evidence comes out and you are shown to be wrong you will have done irreparable harm to science for a long long time. Other scientists will be rejected for funding in the future because people like you who refuse to come clean will have damaged science so much in the eyes of the public. You know that is true.
Give your predictions  and give time frames. If you do not know say so, and encourage all your AGW supporters to do the same thing. You guys like to throw at us skeptics “what if you are wrong”. I throw it right back at you.
[Response: Conscientious science requires that address all possibilities, and yes, you need to give a sense of how likely these things are. There is clearly a possibility of significant ice sheet collapse (the Eemian shows that), but we don't understand how fast these things can happen. You would have us not mention it because we can't say everything about it? This is stupid. How is science supposed to procede if no-one discusses what the unknowns are or where the uncertainties lie? In five years time we'll have a better idea, but right now we can't give you a time scale. Deal with it. I'm not going to make something up to make you happy. - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 2:44 PM
“Show us why my 1000 year prediction is incorrect.
CO2 increasing at 2 ppm per year and accelerating usually suffices.”
Boy you people really do not know the difference between speculation and hard science. Show me the math of how fast the ice WILL melt.
Comment by Richard Wakefield — 9 Sep 2008 @ 2:46 PM
“The science is not yet done, and yet you are convinced that it can’t happen. Based on what? – gavin]”
It’s not the job of the skeptic to provide negative evidence. It’s up you your side to provide the evidence. You should already know that, that’s science 101. Hansen et al are throwing wild speculative numbers of how high sea level will go in the future. It’s their reponsibility to give a time frame. Not mine to show which time frame it cannot be.
[Response: Hansen et al have written many papers on just this issue, all of which are available on their website. They have given their reasoning at some length. Yet you are convinced they must be wrong based on a position of pure ignorance. If you were a real sceptic, you might open your mind to the possibility that your initial idea might in fact be wrong. I've been perfectly up front that there aren't good estimates for the time scale and that paleo information only tells us that it has happened in centuries before and it has changed by meters before. And if something happened in the past, you clearly can't say it is in principle impossible. - gavin]
Comment by Richard Wakefield — 9 Sep 2008 @ 2:50 PM
Curious, are you “Geologist James Richard Wakefield” and “jrwakefield”?
Richard Wakefield — The last vestigaes of the Lauentide ice sheet in northern Canada melted away in the 1930s and 1940s, leaving only some ice caps on Ellsmere and Baffin Islands, Nunavut. So some AGW happened before 1980 CE.
I know of no paleodata which provides good constraints on further ice loss rates. This thread starts with discussing a paper which uses current observations to make a prediction for 2100 CE; looks reasonable.
However, it is not clear that the paper takes the closure of the ozone hole over Antarctica into account. This might well make some difference. Rather than carrying on, why don’t you see if somebody has already published regarding this anticipated event?
If the sea level is rising by 0.1m to 1.3m by 2100, that is a HUGE error bar.
It is still going UP.
Richard, #200 in what scenario? Do you think there is going to be ANY maths (we in the UK can do more than one sum, you know) that show that a warmer pole causes ice to freeze? If you are given a mathematical equation that, when all errors are put in, comes to “reduces by between 300,000sq mi and 1.3m sq mi”, what will you do? Keep complaining that you need better information or the errors don’t include EVERYTHING (and, when asked what is missing, just wave your hand and say “well, you can’t prove you’ve included everything, can you?”) and ask for better numbers.
It is, however, the job of the skeptic to actually listen to the answers he has solicited. If you can’t do that, and if you persist in irrelevant insults, such as “Boy you people really do not know the difference between speculation and hard science,” you are apt to find yourself ignored.
For systems which are highly nonlinear and driven far-from-equilibrium, such as ice sheets displaying endemic instability and structural morphogenesis, any maths that the human race writes down would be silly. The ice sheets have got the human race snookered in every respect.
What maths can be written down for the massive oceanic vortices that are erupting as the antarctic circulation destabilises leading to shock wave transmission and vortex grinding through the undersides of the ice sheets?
What maths can be written down for the seismic bursts sweeping across Antarctica which have now been detected?
What maths can be written down for the ice quakes that are ripping through the Greenland ice sheet? (Humans still seem to have a problem writing down maths that state when a particular earthquake will happen … let alone maths describing the insidious phenomenon being faced with GIS ice quakes).
What maths can be written down for the intermittent oceanic circulations as they falter?
What maths should be written down for coupled ice sheets as oceanic-mediated shock waves exchange between the SH and NH ice caps?
Which of Thom’s catastrophes should be chosen for any of these instabilities?
What maths can be written down for the increasing cascades of marine animals, some from the deepest parts of the oceans and never before seen, as they are swept to shore by the oceanic circulatory intermittencies and disintegrations?
What maths can be written down as ice shelves disintegrate? What maths can be written down for the dispersal of the Larsen B and increasing numbers of other ice shelves as they plop into the seas?
Mother Earth has done the maths, but the human race sure does not have the mental capacity to handle the shock and awe functionals, and multiplicities of nonlinearities, thesholds and singularities.
What is worth asking for is an element of insight and the ability to appreciate the perilous nature of what is unfolding. What is also worth asking for is humility.
It is not worth asking for the maths. Mother Earth will show a representation of it when she is ready.
Er, the picture doesn’t fit the description, at all.
> seismic bursts sweeping across Antarctica
> ice quakes that are ripping through the
> Greenland ice sheet?
Say what? “measured on seismometer” is only the same as “ripping through” for _very_ metaphorical values of “ripping” — what are you reading for your sources?
Try the descriptions found in the pubished science — this stuff is entirely worth attention as published using the authors’ words, without exaggeration.
Science 24 March 2006:
Vol. 311. no. 5768, pp. 1756 – 1758
Seasonality and Increasing Frequency of Greenland Glacial Earthquakes
Göran Ekström,1* Meredith Nettles,2 Victor C. Tsai1
Some glaciers and ice streams periodically lurch forward with sufficient force to generate emissions of elastic waves that are recorded on seismometers worldwide. Such glacial earthquakes on Greenland show a strong seasonality as well as a doubling of their rate of occurrence over the past 5 years. These temporal patterns suggest a link to the hydrological cycle and are indicative of a dynamic glacial response to changing climate conditions.
“The last vestigaes of the Lauentide ice sheet in northern Canada melted away in the 1930s and 1940s, leaving only some ice caps on Ellsmere and Baffin Islands, Nunavut. So some AGW happened before 1980 CE.” Prove it. Peer reviewed paper that supports that claim please.
“Very simple science says that CO2 causes global warming. Very simple science shows that a huge amount of CO2 now in the atmosphere is anthropogenic in origin.” But the interactions within the climate, the number of variables involved is not simple. That’s why millions are spent on super computer to try and model it. It’s not simple at all. If you think it is then that is why you are not skeptical of these wild alarmist claims made by the AGW community.
“If the sea level is rising by 0.1m to 1.3m by 2100, that is a HUGE error bar.
It is still going UP.” and has been for 12,000 years.
“Richard, #200 in what scenario? Do you think there is going to be ANY maths (we in the UK can do more than one sum, you know) that show that a warmer pole causes ice to freeze? If you are given a mathematical equation that, when all errors are put in, comes to “reduces by between 300,000sq mi and 1.3m sq mi”, what will you do? Keep complaining that you need better information or the errors don’t include EVERYTHING (and, when asked what is missing, just wave your hand and say “well, you can’t prove you’ve included everything, can you?”) and ask for better numbers.
So what do we get out of our efforts?”
Look, it should be simple to put a minimum on how fast the ice in Greenland can melt. Example. Assume that the area does not freeze at all for X number of years. How long would it take to melt all the ice? That’s the fastest it can possibly melt. Then you have to extend that time for every day it is colder that OC according to the IPCC worse case increase temp, then extend it for every snow fall that is less than loss. Then you will have a ball park range of years in the future it would take to melt all that ice. Then do the same thing for Antarctica. Someone must be able to do such a calculation. I suspect that it would take at least 1000 years. And since much can change in 1000 years it makes any meaningful prediction purely academic. But what it does do is end these wild prediction where the public thinks these worse case scenarios are imminent, not hundreds or even thousands of years away.
Imagine the impact Gore would have if he qualified his picture of New York submerged if he added the qualifier: “but this will take at least a thousand years to happen.” His alarmism would die immediately., and he would lose his message.
I AWAYS listen to all sides. I have YET to see anyone here answer my question. 
Comment by Richard Wakefield — 9 Sep 2008 @ 8:16 PM
On decommisioning nuclear plants that are presently at sea level: they actually have to be completely disassembled and removed to higher ground. The London Dumping Convention does not permit the disposal of nuclear waste at sea. So, the Humboldt Bay power plant, which has been decommissioned with the core parts stored on site, will have to be redecommisioned in the face of sea level rise.
The reason power plants are built at sea level is because there is plenty of cooling water there. Sea level rise is going to force some of these to close early driving up the cost of electricity as a result.
208. Mr Roberts, I read the Ekstrom paper when it came out so very long ago. Don’t cite such old work to me when challenging the words used to describe nonlinearities.
Please go away and find some uptodate cites to throw at me to challenge the descriptive words used for discontinuous and abrupt behaviours. Please go away and get a cite on the Richter-equivalence level of the ice quakes happening now on GIS. Once you have got those Richter-equivalence numbers, I suggest you make a list of the adjectives that you suggest might be appropriate to describe the abrupt dynamics.
The nature of discontinuities are such that they breed dramatic change. If you don’t like the words naturally appropriate to describe such abrupt things that’s tough.
Comment by Discont In Uity — 9 Sep 2008 @ 11:10 PM
Mr. Richard Wakefield said at 8:22 pm on 9 September 2008:
“Look, it should be simple to put a minimum on how fast the ice in Greenland can melt. ”
Excellent. May we return to discussing the Pfeffer paper ? I have some difficulty with the assumption that the “gate area” of the outlets will remain the same. Would you or others care to comment ?
Okay, as you’re not the geologist Wakefield of the same name, or JRWakefield (the Canadian software guy) — both frequent commentsrs in climate threads various places online. Are you any of the JR Wakefields who have long histories in climate discussions online?
If you’re brand new to this, people will, I think, cut you more slack if you make clear you’re not them.
Taking two of your questions, trying to be helpful here:
You can look this up for yourself. For questions answerable by maps an image search is often useful:
> it should be simple to put a minimum on how fast the ice in Greenland can melt.
Frequently answered question. It depends.
!) the ice stays in place and melts slowly from the edges, top, and bottom (the old paradigm up to a few years ago) or
2) the ice breaks up and melts in pieces (see glacial earthquakes, outburst floods, water courses under ice caps, Lake Vostok, radar mapping and much else changing).
That’s not a simple A or B, “solid or crushed ice” question.
Look up, for example, deep radar maps of Antarctica (Google image search again).
Gavin, reading your thoughts about Antarctica i can’t help but wonder.
‘Sea Level, Ice, and Greenhouses — FAQ ‘ at http://www.radix.net/~bobg/faqs/sea.level.faq.html indicates that there seem to exist a real possibility
” That West Antarctica can collapse much faster than Greenland relies on another oddity of the West Antarctic geometry. Most of the ice sheet base rests well below sea level (500 – 1000 meters below). The important oddity is that as you move further inward, the land is further below sea level. So, consider a point near the grounding line (the point on land where the ice shelf meets the ice sheet). Ice flows from the grounded part into the floating part.
The rate of flow increases as the slope (elevation difference) between the two sections increases. Extra mass loss in the ice shelf means that the shelf becomes thinner (and lower) so more ice flows in from the ice sheet. This makes the ice sheet just a little thinner. _But_ at the grounding line, the ice sheet had just enough mass to displace sufficient water to reach the sea floor. Without that mass, what used to be ice sheet begins to float. Since the sea floor slopes down inland of the grounding line, the area of ice sheet that turns into ice shelf increases rapidly. More ice shelf means more chance for ice to be melted by the ocean.
The collapse mechanism has a mirror-image advance mechanism. Should there be net accumulation, the ice sheet/shelf can ground out to the continental shelf edge. Go back to near the grounding point. This time add some excess mass to the ice sheet/shelf. This thickens the system to ground ice shelf. The grounded ice shelf takes area away from the ocean ablation zone, which makes the mass balance even more in favor of accumulation. So the advance can also be a self- accelerating
As we, as I understand it, have found that there is an abundance of ‘ice-tunnels’ under the ice undermining the stability of the ice-sheet and accelerating its collapse why look at the surface. I know that this rapport from Robert Grumbine at email@example.com is from -97 but its conclusions seems even more dangerous now considering those ” subglacial water system beneath the West Antarctic ice sheet (WAIS) ..who.. is causing scientists to rethink the mechanisms that control the flow of ice streams into the Ross Ice Shelf and ultimately into the Southern Ocean. ”
I have a distinct feeling that we have already passed our point of no return here. And the idea of a moratorium on all CO2 emissions won’t make a difference for us the nearest decades at least, considering that most scientists consider the cycle from CO2 being released until returning now to be at least a hundred years (?) if I got it right. And the ‘CO2 heat-sinks’ are getting saturated so what will take it up and ‘isolate’ it after those are ‘filled’?. What about the rising water temperatures in our oceans, and also, how will the rising acidity influence the deposits of methane under water?
If the frozen methane hydrate under water starts to release its methane it will make no difference if its cycle only is twelve years, right. It all hangs together as someone said. To me IPCC seems more about lifting forward the lowest common nominator than about ‘keeping to the middle’. So what are your thoughts on that?
I am no expert on this topic, but:
“Example. Assume that the area does not freeze at all for X number of years. How long would it take to melt all the ice? That’s the fastest it can possibly melt.”
This is clearly underestimating the complexity of the issue. “The area does not freeze” is not nearly enough information for predicting the time it will take. It will depend on the weather: how much wind, how much rain, what temperature do we have? And how will the ice sheet dynamics respond (in particular: what happens to the flow speed of the glaciers?). Those aren’t easy questions at all.
Richard Wakefield says: “Look, it should be simple to put a minimum on how fast the ice in Greenland can melt. Example. Assume that the area does not freeze at all for X number of years. How long would it take to melt all the ice? That’s the fastest it can possibly melt.”
Good Lord, Man. Do you realize the astounding ignorance in that statement? You do realize that ice melts very differently if you break it up so it has more surface area, don’t you? And that if you’ve got water running through crevasses, that it will speed up melt? And that if it slides into the Ocean, and calves into glaciers, it will melt faster. Sounds to me like another case of thinking anything you don’t understand must be easy.
Now think about this Richard. If you can be so astoundingly wrong about this, are you willing to maybe entertain the possibility that you could also be clueless about the climate as well? Think it might be worth considering?
“Thomas Lee Elifritz Says:
9 September 2008 at 10:52 PM
I have YET to see anyone here answer my question.
Have you ever considered doing your own research?”
If I had access to data and super computers I would.
“The heat capacities of the ocean and ice sheets are fairly straight forward, what is somewhat less than straightforward are the integrated forcings over time.
What is not misunderstood is the result of 2500 ppm atmospheric carbon dioxide. Clearly ALL of the ice will be gone in ‘on the order’ of roughly a millennium.”
What evidence do you have that we will reach 2500 ppm CO2? 450 ppm is projected in the future as a maximum is it not? So you are agreeing with me that it will be 1000 years. At 2500 ppm? If so then it will take much longer than 100 at the 450 wont it. Thus, do yu agree then that RC should call Hansen and Gore on the carpet for not giving a time fram and leaving misinformation in the mind of the public? Again, how much punch would Gore have if he had to admit that it would be a millennium at the earliest for New York to be under 25 feet of water?
“Also not misunderstood is the nonlinear evolution of the result, whether the timescale be 100 years or 1000 years.” So that is an excuse to not give it a try?
Look, people. This is real simple. You try a thought experiment first. This is done all the time in science as a starting point. Take the ice mass of Greenland and float it in the middle of the Pacific. How long would it take to melt? Then start adding real world parameters to the equations and see what effect this has on the duration of melting. What’s the problem people? This is science, not religion. Seems people here are trying to come up with any excuse NOT to find out. Or are you afraid of what the result may show?
[Response: yes, that must be it. Greenland ice = 6 * 0.7 * 5.1 * 10^14 = 2x10^15 m3 equivalent fresh water, latent heat required to melt = 1000 * 334000 * 2 * 10^15 = 6.7 x 10^22 J. Big number right? Available sensible heat in the middle of the Pacific (say one tenth ocean area, mean temperature 20 deg C, mixed layer depth 50 m) = 1.5 x 10^23 J. Uh-oh... Amount of heat added to the oceans over the last 50 years? 2 x 10^23 J (and that was just to the mid-90s). Whoops... Estimated energy addition every year (assuming 0.8 W/m2 imbalance): 1.3 x 10^22 J. Implied time to melt just using new extra energy? 5 years. Now what have we learnt from this? - gavin]
Comment by Richard Wakefield — 10 Sep 2008 @ 8:12 AM
“Okay, as you’re not the geologist Wakefield of the same name, or JRWakefield (the Canadian software guy)” That I am, you were not clear.
What is your point about the Laurentide? Gaven’s claim was: #192 “Collapsing ice sheets have lead to SLR of meters per century in the past (MWP 1A, or even the early Holocene final collapse of the Laurentide). We know that 4-6 meters of sea level are consistent with a further warming of the poles of 3 to 5 deg C (compare to the Eemian). Collapse of the WAIS is not a fiction. It has happened before. But though no-one can say how fast it happened,”
Bingo. First there is no way of knowing how high the average global temp will go over any time frame, hence there is no way of knowing how long it will take to melt Greenland.
Comment by Richard Wakefield — 10 Sep 2008 @ 8:25 AM
Re 221 and re 222:
Both of you are not following. Of course it’s complex. That why the radical predictions by Gore et al cannot be trusted! If it’s so complex how can they come up with ANY prediction at all?
[Response: They don't. They do say that the uncertainties are very large - and uncertainties cut both ways. If you have no information, than you can't rule anything out. We have some information and so we can. But not very satisfyingly. - gavin]
You are also missing the whole point of a thought experiment. You start simple and then proceed to add more and more complexity until you think you have a model of reality. That’s what climate models do. If you are claiming it is too complex to calculate then you are admitting defeat. You are also admitting that all of climate science is too complex and hence no predictions of any kind can be done.
[edit - no Gore-bashing]
Comment by Richard Wakefield — 10 Sep 2008 @ 8:43 AM
“[Response: yes, that must be it. Greenland ice = 6 * 0.7 * 5.1 * 10^14 = 2×10^15 m3 equivalent fresh water, latent heat required to melt = 1000 * 334000 * 2 * 10^15 = 6.7 x 10^22 J. Big number right? Available sensible heat in the middle of the Pacific (say one tenth ocean area, mean temperature 20 deg C, mixed layer depth 50 m) = 1.5 x 10^23 J. Uh-oh… Amount of heat added to the oceans over the last 50 years? 2 x 10^23 J (and that was just to the mid-90s). Whoops… Estimated energy addition every year (assuming 0.8 W/m2 imbalance): 1.3 x 10^22 J. Implied time to melt just using new extra energy? 5 years. Now what have we learnt from this? - gavin]”
No, don’t add any more heat than there is today. That’s unfair. Just today’s temp. Some icebergs last years in the oceans before completely melting, much smaller than Greenland.
Then start to change the numbers by dropping the temp (higher lattatude). Then add in some freezing time. Then add in more acculated snow fall.
[Response: You asked for how long it would take for Greenland to melt in the central Pacific, the first number indicates that there is plenty of energy to melt all of it. So the only determinant of the time scale is the surface area - Greenland diced into ice cubes would melt immediately. But this is nothing to do with anything. - gavin]
“In the most extreme scenario, using a carbon dioxide level of 1,000 ppm, the study predicts temperatures to rise by 8° Celsius (18° Fahrenheit) by the year 2050. This, in turn, would raise sea levels by 7 meters (23 feet) in a thousand years.”
[Response: Part of piece you didn't quote: "We're not saying how long it will take to get to the three degrees or how long it will take to lose the ice sheet,". Note also the absence of a dynamic ice sheet response in the model they used, rendering all discussions of timescale rather problematic (as the authors themselves acknowledge). - gavin]
“Although current cumulative carbon dioxide emissions are on the order of 350 GtC, total emissions may reach 2,480 GtC by AD 2100 under worst-case scenarios — so unless emissions are curbed, runaway melting of Greenland may be triggered in the coming centuries.”
[Response: Yet another model with no ice sheet dynamical response: "this study probably underestimates the impact of the rapid dynamics of the Greenland ice sheet". ]
“The Greenland ice sheet is all but doomed to melt away to nothing, according to a new modelling study. If it does melt, global sea levels will rise by seven metres, flooding most of the world’s coastal regions.
Jonathan Gregory, a climatologist at the University of Reading, UK, says global warming could start runaway melting on Greenland within 50 years, and it will “probably be irreversible this side of a new ice age”. The only good news is that it a total meltdown is likely to take at least 1000 years.”
[Response: Your point? All of Greenland didn't disappear even at the Eemian. - gavin]
“The global warming doomsday writers claim the Greenland and Antarctic ice sheets are melting catastrophically, and will cause a sudden rise in sea level of 5 or more metres. This ignores the mechanism of glacier flow which is by creep. Glaciers are not melting from the surface down, nor are they sliding down an inclined plane lubricated by meltwater. The existence of ice over 3 km thick preserving details of past snowfall and atmospheres, used to decipher past temperature and CO2 levels, shows that the ice sheets have accumulated for hundreds of thousands of years without melting. Variations in melting around the edges of ice sheets are no indication that they are collapsing. Indeed ‘collapse’ is impossible.”
[Response: You are just erecting strawmen here. No one has claimed there will be a "sudden rise in sea level of 5 or more meters", and the claim that the ice sheets haven't melted in hundreds of thousands of years is only true for a complete melt. But they have lost meters of sea level over that time - including a collapse of the WAIS. So it isn't impossible at all. And to claim that because a "sudden 5 m rise" is unlikely, that means there is no problem is just idiocy. - gavin]
Comment by Richard Wakefield — 10 Sep 2008 @ 8:59 AM
Although the reply to #223 gave me a big laugh, on a general point surely there are more pressing implications from this subject than indulging (and rewarding) such breathtaking, relentless rude ignorance? I’d love a little bit of reflection on my #180, for example…
I’m still waiting for peer reviewed papers showing that 1850-1945 warming was due to human emitted co2.
Since there isn’t any, then the following logic is implied.
Rate of sea level has been within a narrow range averaging 1.7mm.yr for the past 110 years at least. This is observed from in situ measurements. The first 100 years was during a warming trend where humans were a very small contributor of CO2 emissions (14% of today’s).
Thus during the first 100 years of this warming trend we could not have been the contributors due to CO2 emissions. Thus the rate of sea level from that warming trend cannot be anthropic.
Since the rate of sea level rise in the last 70 years has not broken through the decadal variation, then the current sea level rise cannot be anthropic in spite of an 8 fold increase in CO2 emissions.
Breaking through the decadal variation is important. The current rate of 2.4-3.2mm/yr is within this variation, hence not an indicator of AGW. Not until it breaks through that variation can one make the claim that it is finally accelerating.
Comment by Richard Wakefield — 10 Sep 2008 @ 10:39 AM
Richard, Do you understand the utter irrelevance and futility of ranting against the science on a blog whose whole purpose is to try to teach you about that science? Want to learn the science? Great, ask some relevant questions to fill in the blanks in your understanding in a respectful way.
Don’t like the science? Well, tough. Unless you want to go out and publish a whole bunch of papers in peer-reviewed journals that overturn the foundations of 150 years worth of climate science, you’re kind of stuck. See, try as they might–and they have really tried–climate scientists have not been able to come up with theories/models that explain the climate with a CO2 sensitivity less than 2 K/doubling. You are welcome to try, but without your own publication record showing it can be done, people who really know the field probably aren’t gonna take you seriously.
“[Response: Part of piece you didn’t quote: “We’re not saying how long it will take to get to the three degrees or how long it will take to lose the ice sheet,”. Note also the absence of a dynamic ice sheet response in the model they used, rendering all discussions of timescale rather problematic (as the authors themselves acknowledge). - gavin]”
EXACTLY!!! You just agreed with my position. Thus, again, to not include this caveat when giving predictions is irresponsible. So it could very well take thousands of years to all melt, or as you note “All of Greenland didn’t disappear even at the Eemian. – gavin]” So you now disagree, and will correct, anyone here who claims it will all melt and in short time, right? You will publicly claim to the MSM these uncertainanities right?
[Response: What are you arguing with? If all you wanted was a statement that all of Greenland is not likely to melt, then why didn't you stop at the opening post paragraph 4? No-one has claimed all of Greenland will melt in a short time. - gavin]
Comment by Richard Wakefield — 10 Sep 2008 @ 1:16 PM
““A” is not caused by AGW. “B” started with “A” and continues through to “C”. “C” is caused by AGW, but since “B” started and is unchanged since “A” then “B” cannot be from AGW.
[Response: Yes. But wrong. You have no information on the cause of B, nor on its invariant continuation. You can do better than this. - gavin]”
Do you? Do you have peer reviewed papers that shows that the cause of B (sea level rise) is because of AGW?
[Response: Yes. Domingues et al (2008). - gavin]
Comment by Richard Wakefield — 10 Sep 2008 @ 1:18 PM
from “Climate change and trace gases” by Hansen et al
“Despite these early warnings about likely future nonlinear rapid response,
IPCC continues, at least implicitly, to assume a linear response to BAU forcings.
Yet BAU forcings exceed by far any forcings in recent palaeoclimate history.”
“Part of the explanation for the inconsistency between palaeoclimate data and
IPCC projections lies in the fact that existing ice sheet models are missing
realistic (if any) representation of the physics of ice streams and icequakes,
processes that are needed to obtain realistic nonlinear behaviour. In the absence
of realistic models, it is better to rely on information from the Earth’s history. …
That history reveals large changes of sea level on century and shorter timescales.
All, or at least most, of glacial-to-interglacial sea-level rise is completed
during the ca 6 kyr quarter cycle of increasing insolation forcing as additional
portions of the ice sheet experience albedo flip. There is no evidence in the
accurately dated terminations (I and II) of multi-millennia lag in ice sheet
Hansen’s case is like the corpse of poisoned Pope at a Borgia family picnic. Something of an embarrassment all around. There’s nothing (outside the geological record) for scientists — who want to stir the world to action entirely with decorum and sobriety — to point to in their print outs and models. And yet there’s the stubborn geological record with its sub-millennial transitions. And, of course, there’s the awkward agreed-upon magnitude of the forcing from GHGs (much greater than orbital insolation changes).
Were I a scientist with Hansen’s understanding of all the physics and processes involved in these issues, it would probably take elephant tranquilizers to get me unconscious at night. This isn’t Area 51 stuff. Nobody seriously disagrees with the speed with which glaciation terminates. Nobody seriously pegs the forcing due to changes in insolation as more than a fraction of the forcing due to GHGs. Which is where my dead-Pope-at-the-Borgia’s image comes from. It would be impolite and impolitic to suddenly grab people by the lapel and scream, but apparently we’re really going to need a trickle of water at our feet to get moving.
Well? Shall we go?
Pull on your trousers.
Pull on your trousers.
You want me to pull off my trousers?
Pull ON your trousers.
(realizing his trousers are down). True. He pulls up his trousers.
Well? Shall we go?
Yes, let’s go. They do not move.
“Do you? Do you have peer reviewed papers that shows that the cause of B (sea level rise) is because of AGW?
[Response: Yes. Domingues et al (2008). - gavin]
Improved estimates of upper-ocean warming and multi-decadal sea-level rise
Nature 453, 1090 (2008). doi:10.1038/nature07080
Authors: Catia M. Domingues, John A. Church, Neil J. White, Peter J. Gleckler, Susan E. Wijffels, Paul M. Barker
& Jeff R. Dunn
Changes in the climate system’s energy budget are predominantly revealed in ocean temperatures and the associated thermal expansion contribution to sea-level rise. Climate models, however, do not reproduce the large decadal variability in globally averaged ocean heat content inferred from the sparse observational database, even when volcanic and other variable climate forcings are included. The sum of the observed contributions has also not adequately explained the overall multi-decadal rise. Here we report improved estimates of near-global ocean heat content and thermal expansion for the upper 300 m and 700 m of the ocean for 1950–2003, using statistical techniques that allow for sparse data coverage and applying recent corrections to reduce systematic biases in the most common ocean temperature observations. Our ocean warming and thermal expansion trends for 1961–2003 are about 50 per cent larger than earlier estimates but about 40 per cent smaller for 1993–2003, which is consistent with the recognition that previously estimated rates for the 1990s had a positive bias as a result of instrumental errors. On average, the decadal variability of the climate models with volcanic forcing now agrees approximately with the observations, but the modelled multi-decadal trends are smaller than observed. We add our observational estimate of upper-ocean thermal expansion to other contributions to sea-level rise and find that the sum of contributions from 1961 to 2003 is about 1.5 ± 0.4 mm yr-1, in good agreement with our updated estimate of near-global mean sea-level rise (using techniques established in earlier studies) of 1.6 ± 0.2 mm yr-1.
Gavin, where does it say in this paper that the cause of sea level rise is due to AGW?
[Response: You're right, ocean warming must be due to some other mysterious energy force that is causing the planet to be out of energy equilibrium. - gavin]
Comment by Richard Wakefield — 10 Sep 2008 @ 1:38 PM
“[Response: What are you arguing with? If all you wanted was a statement that all of Greenland is not likely to melt, then why didn’t you stop at the opening post paragraph 4? No-one has claimed all of Greenland will melt in a short time. - gavin]”
Gore does it implicitly by showing a modern New York getting swallowed by 25 feet of sea and says it’s from Greenland melting. Greenpeace does it which is why they are being sued in Spain. You are missing my point.
You are agreeing with me that this cannot happen in less than 1000 years. Even agreeing it is unlikely to all melt at all.
So we come back to the main question. When are you going to publicly tell the MSM this and ask Gore to include this caveat in his presentations?
[Response: Gore stated correctly that if Greenland melts it will cause sea level to rise 6 meters. I would have been happier if he said that the timescale for such a thing is likely long but uncertain. But I have no confidence that the timescale is 1000 years, and I have no confidence that this implies that sea level rises of 1 meter or more can't happen in a century. Greenland is not the only ice sheet remember and all of the estimates you quoted did not include dynamic ice processes. Both Gore and the MSM read this blog, but everything here was stated in the opening post already. - gavin]
Comment by Richard Wakefield — 10 Sep 2008 @ 1:43 PM
Richard Wakefield (223) wrote “If I had access to data and super computers I would [do my own research].” There are plenty of accessible papers to read and ice core data, for example, is easily available; a super-computer is not required, although internet access is highly desirable.
From the NOAA Paleoclimatology web site one can obtain, for example, the Petit et al. Vostok temperatures for the Eemian. From this one sees that the temperatures there where above recent temperatures for over 4,800 years; during this interval, the Greenland ice sheet partially melted away, there being a graphic of the result reproduced in IPCC AR4.
you can compute the equilibrium warming due to additional CO2 for any period for which CO2 concentrations are available. For example, from 1750 CE to 1850 CE, anthropogenic CO2 contributed 0.08 K (equilibrium) warming to whatever the actual temperture cahnge was. Now correct this for the very fast (less than 7 years) warming, about 60% of the equilibrium to obtain 0.05 K, about half the effect of the change in TSI over a typical sunspot cycle.
Comment by David B. Benson — 10 Sep 2008 @ 3:41 PM
Dear Mr Wakefield, why should I trust your gut feelings about how fast the Greenland ice will melt. You give me no reason to believe you know the first thing about these matters.
For your information, the main method by which an ice sheet melts is not due to solar energy, which will not change in Greenland over the next century, but due to the transfer of latent heat from water vapour. Ben Nevis in Scotland, roughly the same height as the Greenland ice sheet receives 4 m (12 feet) of precipitation per year. The latent heat of ice is 333 J/g, the latent heat of water vapour is 2,500 J/g. That means that there is enough latent heat released above Ben Nevis by condensation to melt 30 m (100 feet) of ice each year. In one hundred years 3 km of ice would melt, which is about the average depth of the Greenland ice sheet.
When the Arctic sea ice disappears, there will be an additional source of water vapour to melt the Greenland ice. And as the ice melts its upper surface will sink to lower and warmer altitudes. It is just feasible that the Greenland Ice could be gone this century :-(
Re Hank @ 215: “Okay, as you’re not the geologist Wakefield of the same name, or JRWakefield (the Canadian software guy) — both frequent commentsrs in climate threads various places online…”
Hank, he is indeed the Canadian software guy (see his reply @ 224) from Kamoka, a suburb of London, Ontario, and he is anything but brand new at this, “this” meaning infesting and disrupting global warming/climate change threads with his pompous and ludicrous hand waving and windmill tilting.
Since it now seems clear that Richard Wakefield doesn’t actually want to do any research, I’m looking for a volunteer to go to the NOAA Paleioclimatology web site, acquire the NGISP (northern Greenland) temperatures and determine the length of the Eemian interglacial, here defined as from the year the temperature first rose to that of the local 1850 CE temperature until it once again falls below that temperature. That will provide a good estimate for the time interval required, under those prevaling conditions, for the Greenland ice sheet to raise the sea level its share of the 4–6 observed meters. (Surely WAIS contributed ssome as well.)
Comment by David B. Benson — 10 Sep 2008 @ 6:06 PM
“you can compute the equilibrium warming due to additional CO2 for any period for which CO2 concentrations are available. For example, from 1750 CE to 1850 CE, anthropogenic CO2 contributed 0.08 K (equilibrium) warming to whatever the actual temperture cahnge was. Now correct this for the very fast (less than 7 years) warming, about 60% of the equilibrium to obtain 0.05 K, about half the effect of the change in TSI over a typical sunspot cycle.”
So in other words no meaurable effect at all. Problem is, we cannot rewind the clock and take our CO2 out and see what happens can we. Thus I maintain, 1850-1945 CO2 emissions had virtually NO effect on the temperature. It would have risen anyway. Hence my logic example stands. The current rate of sea level, 1.7mm/yr over the last 110 years, cannot be from AGW. The current decadal measurement is due to varations, that even the paper Gavin suggested, shows is just normal variation.
Comment by Richard Wakefield — 10 Sep 2008 @ 8:10 PM
“Dear Mr Wakefield, why should I trust your gut feelings about how fast the Greenland ice will melt. You give me no reason to believe you know the first thing about these matters…. It is just feasible that the Greenland Ice could be gone this century.”
Not according to Pfeffer et al. They give an upper limit. That’s what this is all about. So your dire predictions are not agreed with by the peer reviewed papers.
And that 1000 year is not from me, don’t even try to shoot the messenger (common dogmatist tactic), go after the people who published the papers I quoted. That’s how science works. Publish in a peer reviewed paper showing why they are wrong and you are right. Until then, what you present is nothing but faith based suppositions.
Comment by Richard Wakefield — 10 Sep 2008 @ 8:14 PM
It has been amusing at times to watch Richard Wakefield tie himself in knots trying to undermine AGW. But frankly it is troubling to think of the amount of time that Gavin and other scientists have wasted on this guy. I suppose it is necessary to refute nonsense when it is presented as science, but there is nothing you can say that will change Wakefield one iota. He is a troll, and he has dominated the discussion long enough.
I couldn’t agree more with #247. Real Climate is a place for serious discussion, not for denialists trolling whose response to logic and science is simply to shout louder and with seeming ever-greater arrogance and ignorance. This is starting to look like any other random, unmoderated internet forum.
Again, the wider issues are being ignored, and the consequences could not be more serious. Again I ask – what is the most appropriate response by other climate scientists to Hansen’s contention that SLR is very soon (months) to pass a tipping point where it cannot be stopped – however long that eventual process takes? While Hansen engages the world’s leaders on the issue, is it right that he does this (seemingly) alone?
“Gore does it implicitly by showing a modern New York getting swallowed by 25 feet of sea and says it’s from Greenland melting. Greenpeace does it which is why they are being sued in Spain. You are missing my point.”
Nope, he didn’t put any timeline on it and given how slow change in NYC happens in construction, why would it change much over a century? And if greenland can melt in five years based on the extra heating at that lattitude, it could be true.
Your “point” is wrong too because you have considered it only a thousand years for greenland ice sheet to melt. But answers given to you show this is unlikely.
Will NYC change in 5-10 years so much that you could tell it wasn’t todays NYC? No. Your refutation is wrong.
The comments section do not do justice to some of the excellent research coming out of Greenland. I cannot believe I am reading about rain weakening a glacier. How many days have I spent in the rain on a glacier, including three inches in one day this summer. how many glaciers exist in a temperate climate where rain is the dominant weather pattern for 200-300 days a year from Patagonia to Alaska. Obviously rain does lead to surface melt and but it does not weaken a glacier. We had the opportunity this August, not the first time, to hideout in a glacier cave, stream carved channel at base of glacier, during a rainstorm. Even with all of that rain, and the air temp of 10 C, outside the cave, it is interesting to see the new ice on the floor of the cave and at the glacier-becrock interface. Most of the good research is focussed on the acceleration of marine terminating glaciers, a detailed analysis of these is needed here soon, but not today. In terms of melting a recent paper examines the heat balance terms leading to melting of the Greenland Ice Sheet. They identify that depending on your elevation the terms vary in importance. However, short wave radiation is the domninant term, with sensible heat flux becoming important at the lower elevations and latent heat flux being minor. Note Figure 7 in the paper. http://www.the-cryosphere-discuss.net/2/711/2008/tcd-2-711-2008.pdf
Does this not prove that recent mid-holocene temperatures may have been higher globally than present?
It is often cited that equatorial regions may have been cooler during the mid-holocene warm period and therefore overall global average temps were NOT above present – so what climate mechanism would allow this and could [said mechanism] repeat itself?
[Response: Global sea level was not 6m higher 8000 years ago. Perhaps you would like to point out where the Greenland sized ice sheet that must have grown since then could be found? The best global estimates instead indicate a gentle rise throughout this whole period. As for these two shells from India, it's most likely that either local uplift has been underestimated, or that assessments of the local interpretation might be incomplete. This is a difficult thing to do accurately, but the weight of evidence is clearly against a Holocene sea level stand higher than today. - gavin]
agreed that there is uncertainty on uplift but I would not be so quick to dimiss ALL studies on mid-holocene sea levels because they may ALL have uplift wrong – and there are quite a few which I will try and find again. I only saved the one I posted above! As I said they vary between 0.5m and 6m so big difference of opinion on all.
makes strong case that mid-holocene warming was northern hemisphere only, but I haven’t seen evidence there was so much orbital variation 3500 years ago (I pick this date as it is within the range as a date having possibly higher sea level than now). Fair enough to say milti-millennial variations, Milankovich, precession etc, but if you could point me to a study that cites orbital differences 3500 years ago I would rest easier on this matter!
[Response: Orbital variations peaked in the early Holocene, so I'm not sure what you are looking for. Look at Chapter 6 (fig 6.9) for an assessment of Holocene changes by latitude. - gavin]
It seems that we may be having some anomalies in post numbers. I was agreeing with Ron Taylor, #248, not #247. (If the confusion is mine, then I apologize for an unnecessary post.) But it does seem that several other posts are off by a number or two, and it does make the discussion noticeably harder to follow. For my part, I will try to be really scrupulous in getting the right number up there.
[Response: It's related to the moderation of comments - not your fault. But feel free to use the permalink for each comment as a link to a reference. That doesn't change. - gavin]
Volcanoes and industrial aerosols are negative forcings.
But the absence of volcanic eruptions can behave as a positive forcing when the system has a component with a long time constant. The early 20th-century lull in volcanic activity is at least partially responsible for early 20th century warming.
Just for laughs, I ran the volcanic forcing estimates from GISS through a zero-dimensional TWO-component model, with a short time constant for one component (a la atmosphere) and a long time constant (30 yr) for the other (a al oceans). I was surprised at the size of the warming caused by the lull in volcanic forcing for the early 20th century.
However, I very much doubt that the anthropogenic impact during the early 20th century was nothing at all. CO2 levels were notably higher than pre-industrial, and the radiative forcing of that CO2 is not zero.
Re #252 where Mauri wrote: “I cannot believe I am reading about rain weakening a glacier.”
I presume that you are referring to my post #242, where I wrote “Ben Nevis in Scotland, roughly the same height as the Greenland ice sheet receives 4 m (12 feet) of precipitation per year.”
Obviously, I did not explain what I was tying to say very well. I was not arguing that the rain will melt the ice. I was arguing that water vapour would melt the ice by losing its latent heat of condensation. The problem is to estimate how much water vapour there would be available to do that. Since the rain falling on Ben Nevis originated as water vapour that had been carried there by winds, then that gives a (very) rough estimate of the amount of water vapour that would be available to melt the ice, provided that it did not condense and fall as rain first.
Once the water vapour does condense, then the rain will only be able to transfer sensible heat to the ice. Even if the rain is 10 degs. C warmer than the ice it will still only melt 10/333 grams of ice for every gram of water. Water vapour melts 2500/333 grams of ice for every gram of water vapour.
FWIIW, I have just checked in Sharp, Robert P. (1960) “Glaciers” , Condon Lectures, Oregon State System of Higher Education, Eugene, Oregon and on page 22 he shows the same calculations as mine for the relative effects of rain and water vapour.
I’ve read Pfeffer et al. and they assume that surface melt will remain constant, hence it is not surprising we disagree. They certainly do not consider the effects of the Arctic sea ice disappearing, which now seems inevitable.
I admit I am surprised by figure 7 from Van dem Broke et al. where sensible heat far exceeds latent heat gain from the air. I can only assume that the air is extemely dry, since it is originating in the polar vortex and passing mainly over land and cold sea ice on its route to west Greenland. Without the Arctic sea ice, the air will pass over a wet Arctic ocean and so will be more humid than it is at present.
One problem with science these days is that it is extremely compartmentalised. Those who know about glaciers work separately from those who work on sea ice. The consequences to the general circulation from loss of sea ice is yet another discipline. As an amateur I feel it is my duty to wave a red flag when I see an obstruction on the railway track of which the engine driver and the signal box are unaware.
Thanks, Gavin. I hate to display the full extent of my naivete here, but–so I can click on the date/time line to pull up a index number for the comment, such as this one for my #256: index.php?p=598#comment-98264
Should I just paste it in as I did above, or is there a slicker/clearer way to do this?
[Response: Use html tags: <a href="#comment-98264" > </a> like so. - gavin]
Personal communication from an engineering manager at a large government agency. He writes and reviews Requests For Proposals for both state and federal projects in the south-western US. RFPs are confidential documents. I do not know which project he was working on at that time.
Normally, an engineer could base his design on historical climate data. However, if he had reasonable cause to believe that such a design basis would not protect the public safety, then it is not an acceptable basis of design. There is a reasonable expectation of SLR, thus historical data is not a defendable basis of design.
It was late at night, and he was stressed enough that he had switched from merlot to brandy.
The IPCC SLR estimates do not contain dynamic ice movements. Dynamic ice sheet movements are a reasonably foreseeable factor, and therefore must be considered in the development of the design basis of critical public safety infrastructure. I think everyone is in agreement on that. I think everyone is in agreement that not much ice can melt in place. The question is whether there are any mechanisms that would allow substantial volumes of ice to fall (WAIS) or be flushed into the sea (GIS).
We have never seen the breakup an ice sheet first hand. Thus, we cannot rely on what is familiar. We have to look at physics and material science. We need to do this in a hurry, because the engineering managers are drinking up all of our brandy
I can’t find it with the online search tools I know how to use. I’d guess that is a wish in an RFP — some drafter is trying to get some contractor to promise them an impossible result. If it’s specified as being assurance about the _future_ two centuries rather than the historical experience, it’s even more wishful.
Any legal requirement would be public information and ought to show up in the indexes. That’s all I can say.
As always, trust only after you can verify what people claim.
I was confused by the number you used since you seemed to be agreeing with Richard Wakefield response to me :-(
But I thought I would mention that if you use the name the person as well as the post number then that avoids most confusions. I think most regulars do that anyway, having been caught out by the renumbering ourselves.
And I do empathize with your engineer friend. If he’s seriously trying to design for the worst case possible in the next 200 years, I guess the question is whether his customers’ grandchildren are going to experience anything as extreme as a methane clathrate blowout and rapid change like the PETM may have had.
The first two here are cautionary. I can’t imagine designing infrastructure for this:
If you think this is at all likely, you’ll want to go shopping for something well away from most of the troubles — say a large family-owned ranch in Paraguay atop the Acuifero Guarani with a nice big landing strip on it. But who’d think that far ahead, eh?
According to the recent report by the Dutch Delta Commission SLR in a worst-case scenario could be 1.3 meters in year 2100 and 4 meters in 2200, based on the latest scientific insights. But what does this mean for the period after 2200? Could SLR stabilize at around 6 meters, for example, by year 2300 or 2500? Or could it continue, or even accelerate, to 8 meters by year 2300 and 12 meters by 2400? Now Pfeffer e.a. say it could be 2 meters by year 2100, so maybe it could be 6 meters by 2200 and 12 meters by 2300?
Looking at the GIS and WAIS figures, do they mean that in a worst-case SLR could be a maximum of 12 meters by year 2300? Or is this too pessimistic an interpretation? What would be a more appropriate one?
Aaron Lewis makes a valuable point, which brings up once again the difference between scientific conservatism and engineering conservatism. The scientist does not want to say more than he can credibly demonstrate to be true. The engineer has to consider the risk associated with any outcome that is “reasonably” probable. And I assume that the greater the risk, then the lower the probabilities that have to be taken into account. How would you determine the hundred year flood line in coastal areas today? My training is in aerospace engineering, so I probably have not expressed this correctly. But it would seem that the large uncertainties in SLR will pose some real challenges in the civil engineering world. And I imagine a lot of people, like insurance companies, bond investors, etc. will have in interest in how they handle them.
Re # 252
I have hid from the rain in ice caves that are now gone. (We did not climb on rainy days because the ice was too soft. It may not have been the rain, it may have been the water vapor in the air :)
Did you acutally measure and track the strength of the ice?
While ice axes and crampons do not go very deep into the ice, still they offer a sample of ice strength every foot or so up an ice face. Ice screws offer a sample of ice strength 2 ft below the ice surface. How long until the ice deforms under the climbers body weight is a good realtive measure of ice strength. For an ice climber, if the ice deforms too fast, it is unclimbable. We paid attention to ice strength.
My experience is that (surface) ice is stronger on bright, cold, sunny days than on rainy days. Granted, we mostly climbed on smaller bits of ice with much less thermal inertia, but the concept should be similar. I would also note that the differece between strong ice and weak ice may be only a couple of hundred vertical meters.
Mauri, as you may have seen there is an article in the 8/26 Eos about measured runoff from a jokulhaupt that occurred in Greenland about a year ago. What I found most interesting about it was that the amount of direct runoff from the lake was only about 40% of the total, the larger amount being nearly all from frictional melting of the ice by the draining water. Does this throw the Pfeffer et al results into question?
[Response: This isn't a soapbox for you to repeat the same old thing over and again, when you have been given plenty of correct advice (and links to the forcings, and links to the model responses). If you are interested in the real answers to your questions, they lie there. If not, go play somewhere else. - gavin]
Comment by Richard Wakefield — 11 Sep 2008 @ 3:13 PM
Alistair, no it was not your comment on heat transfer via melt that was totally offbase. It was A. Lewis conjecturing on the instant collapse due to rainwater weakening. Reminds me of the reporter I had on a glacier two years ago who thought it could just swallow him up even standing on the solid part. It was a long day for him. Steve, as I recall the hydrologic balance included the jokulhaup, but that did not include all the meltwater in the watershed, thus basal melt would only be a portion of the remainder. But, drat I Recycled that EOS.
Lennart (267) — I’m an amateur at this, but I’ll opine that 12 meters of sea level rise is most likely to take at least six centuries and probabnly more like twelve.
Comment by David B. Benson — 11 Sep 2008 @ 4:19 PM
Mauri, I have that Eos still. Is this what you needed? Else tell me what to look for and I’ll type it in.
“… discharge during the jokulhlaup is calculated to have been approximately 540 cubic meters per second, and the total runoff during the event is estimated to have been 28.8 million cubic meters. Outflow from the ice-dammed lake is estimated to have been 11.3 million cubic meters; the additional 17.5 million cubic meters is due to frictional melting of ice as the flood traveled in contact with the glacier, together with an input from base flow….”
Earlier: “… an accuraccy of 5-10% during low flows; peak flow estimates were less accurate …”
the stations S5,S6 and S9 are at (6Km from ice edge,490m elevation), (38Km, 1020m) and (88Km, 1520m) respectively from table 2. In Figure 3, i read decreases is surface elevation of 17m, 7m and 0m respectively, over 4 yr.
comparing stations S5 and S9, the average slope at the beginning is (1520-490)/((88-6)*1000)=0.0126 . similarly comparing S5 and S6 i obtain 0.0166
at the end of the 4 yr period, the slope between S5 and S9 increase to 0.0128 (1.5%) and the slope between S5 and S6 increases to 0.0172 (increase of 3.5%)
the numbers for the slopes between S6 and S9 are 0.01 increasing to 0.0986
(increase of 0.9%)
my question is: as this slope increases toward the edge of the ice sheet, will it not get oversteepened beyond the angle of repose and thus increase the velocity of the ice sheet toward the margin. i see no measurements of ice velocity at these stations in this paper, i assume because the velocity was too small to measure ?
#254 – I’d love to know which other climate scientists are alongside Hansen (genuine comment). I see plenty of support from afar, but I’m unaware of other prominent scientists following him to international governments – and into courtrooms.
So… is Hansen’s sense of dramatic urgency which can excuse £35,000 of criminal damage correct? Are we, with reasonable probability, near a tipping point on SLR and other effects of climate change? And who else is directly supporting him?
[Response: Hansen's testimony is downloadable here. - gavin]
Apparently DOI lawyers looked at the language in the CAL- FED Delta ROD, the CAL-FED authorizing legislation (Calfed Bay-Delta Authorization Act) and 50CFR17 in view of DOI engineering policy to come up with required confidence levels for various project’s engineering.
I read the plain language of those documents/ESA to require 100% performance for some of these projects. Am I missing something? Are there weasel words that I am just not seeing?
11 September 2008 at 1:21 PM
According to the recent report by the Dutch Delta Commission SLR in a worst-case scenario could be 1.3 meters in year 2100 and 4 meters in 2200, based on the latest scientific insights. But what does this mean for the period after 2200? Could SLR stabilize at around 6 meters, for example, by year 2300 or 2500? Or could it continue, or even accelerate, to 8 meters by year 2300 and 12 meters by 2400? Now Pfeffer e.a. say it could be 2 meters by year 2100, so maybe it could be 6 meters by 2200 and 12 meters by 2300?
Comment by Richard Wakefield — 11 Sep 2008 @ 5:49 PM
I want to weigh in with Guy in support of Hansen. It seems to me that he is about the only climate scientist to put his career on the line and he has continued to weigh in at the government policy level more or less on his own. I have been concerned that he may eventually be ground down, and, frankly, I see him as the only one standing between civilization and disaster, as he formally challenges unwise policy decisions. Gavin and others here are providing a wonderful service, but I am wondering how Hansen can get more support from his peers.
Richard, my God, do your realize what you are saying? Population to decline to 10% of todays in 200 years! Do you understand why that speculation is out there? It is primarily because of climate change impacts brought about by the positions of people like yourself. How does it feel to support a position that could lead to 5 billion or so deaths in the next 200 years?
Aaron, I’m not a lawyer, but I think — I’m fairly sure — that any contract spec to survive a “200 year” weather event — flood, tide, whatever — is referring to the past 200 years’ historical experience.
If there’s a law that’s foreseeing additional anticipated climate change in design specs, I’d like to see it. It would be a good idea.
Re #275: That’s the key phrase, Hank. I’m assumimg from the context that the basal melt component would be negligible. Mauri, to make clear what my question is, if this event can be taken as a guide there seems to be a basis for thinking that the rate of Greenland melt could become decidly non-linear as the volume of meltwater increases. Re Pfeffer et al, did their results take into account this possibility?
That is an interesting article. It recalls the defense of another activist attempting to shut down a different power plant in New Hampshire. It rested on the Right of Revolution in the State Constitution. In that case, the damage was sawing down a pole. A portion of the law goes like this: “The doctrine of nonresistance against arbitrary power, and oppression, is absurd, slavish, and destructive of the good and happiness of mankind.”
surely this is easy to calculate ? let us say that 1g of water falls 1Km. assume for convenience that g is 10m/s^2. the energy released is then 1*10E3*1E6=1E9erg=1E2joule. latent heat of fusion is 80cal/g*4.2J/cal=330J
so 1g of water falling for a kilometer can at best melt 1/3g ice if everything is at the melting point ?Dixo
Ron Taylor Says:
11 September 2008 at 7:23 PM
Richard, my God, do your realize what you are saying? Population to decline to 10% of todays in 200 years! Do you understand why that speculation is out there? It is primarily because of climate change impacts brought about by the positions of people like yourself. How does it feel to support a position that could lead to 5 billion or so deaths in the next 200 years?
Not at all. I was refering to those that are predicting this due to peak oil, not AGW. such as The Long Emergency, and Dieoff.org. I’m not agreeing or disagreeing with them. They are just another extreme view. I’m just saying 200 years is along time in the future. The planet could be in a full blown cooling spell by then, in spite of the models for warming. None of us here will be around to find out and say “told yea!”
Comment by Richard Wakefield — 11 Sep 2008 @ 10:26 PM
Steve, the river coming down from the glacial lake was being studied; a pressure transducer was in place (measuring depth) positioned above bridges at a location with a “well-defined, stable cross sections on bedrock” (that means the flow of water only increased the depth, measured by the pressure transducer). They had already done the work to determine “stage-discharge relationship (R-squared = 0.91) and to convert the stage measurements into a river discharge time series” — and so were instrumented and able to get a detailed record of the event.
The flood traveled about 35 kilometers down the river before it reached the measuring station.
As I read the Cal-Fed Delta authorization, it does not specify years. The law says, such and such agencies (including DOI) *shall* build structures that protect the habitat of various critters. It looks like a requirement for 100% performance, forever.
Talk about long tailed statistics!
It was agency lawyers that interprted that as a 1/10^6 failure rate within 200 years. Since DOI is the enforcing agency for the ESA, that intrepretation would be given deference in court.
I note that the Compehensive Everglades Restoration Plan
was developed by USACE and says,”design for a possible sea level rise of 8 inches in the period 2000->2050″. USACE makes a point of saying they are using numbers from the 1995 US EPA report. However, one sentence jumps out of that report,
“The reader should have no illusions about the
adequacy of the models used in this or any report
projecting future sea level rise.”
That USACE should reference such a report shows the sad state of estimates of sea level rise.
“…how does a layer of paint cost £35,000?” Easy – lawyers got involved &;>)
I did some simple (way too simple, but still…) calculations, based on an approximation of 1e7 km2 of ice melt 2m thick each year. When this energy gets hungry after the Arctic ocean loses its cover and starts devouring Greenland, it will take ~300 years for all of the ice to melt.
Richard, suppose 2 meters of SLR by year 2100 is possible in a worst case, and 6 meters by 2200, what would that mean for densely populated coastal areas? Are we going to move those cities inland? What would that mean for global economic and political stability? An American think-tank, the Center for Strategic and International Studies, took the possibility of 2 meters SLR by 2100 seriously, based on expert opinion, in this report of November 2007: http://www.csis.org/media/csis/pubs/071105_ageofconsequences.pdf
I think it’s important to think such scenario’s through, since the consequences could be enormous if we don’t.
David, if 4 meters of SLR would be possible by 2200, then how much could it keep accelerating during the following centuries? Jim Hansen says that 20 meters of SLR in 400 years was possible about 14.000 years ago: http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_2.pdf
That’s 5 meters per 100 years on average. In what kind of world was this possible? Of course there was much more ice to melt back then, but then the forcings were smaller than now, as Hansen stresses. So do and can we really know how fast the ice could melt in the coming centuries? Let’s say 10 meters by 2300 is possible in a worst-case scenario? How should we deal with that? How should we respond? I suppose we should try to prevent this from happening, if we still can. How fast should we reduce global carbon emissions to stay on the safe side? Hansen thinks we should go back to at least 350 ppm CO2-concentration asap, so we even need to sequester carbon from the atmosphere. IPCC thinks we should reduce carbon emissions by 50-85% below 2000-levels by 2050, just to have a fair chance of staying below 2-2.4 degrees higher temperature, which Hansen thinks is already way too dangerous. And he also mentions peakoil: since we have to find alternatives for oil anyway, why not sooner rather than later? The world is quite rich and can afford it. If we take the risk to postpone this transition, and if SLR and other consequences are more serious than we anticipated, this may seriously reduce our wealth later. How much risk are we willing to take with the lives of our children and their children? I’m 37 now. My sister is 27 and had her first child last week. My niece will hopefully be 70 in 2078. Her children could be 70 by 2105. What kind of world will we leave for them? We all have to adapt to changing circumstances, but we make adaptation much more difficult for our grandchildren if we make their circumstances change too fast, and with no possibility to stop them from continuing to change rapidly. Isn’t that what this whole debate is about in the end?
Brian Dodge Says:
12 September 2008 at 9:34 AM
“…how does a layer of paint cost £35,000?” Easy – lawyers got involved &;>)
I did some simple (way too simple, but still…) calculations, based on an approximation of 1e7 km2 of ice melt 2m thick each year. When this energy gets hungry after the Arctic ocean loses its cover and starts devouring Greenland, it will take ~300 years for all of the ice to melt.
The aircraft were found under 268 feet of ice. That’s over 50 years. Thus the accumulation of ice is about 5 ft per year. In 300 years, that’s 1500 ft of new accumulation. How does this affect the rates of melting?
Comment by Richard Wakefield — 12 Sep 2008 @ 12:19 PM
Re #292 [Richard C]
I disagree completely: a splendid verdict for non-violent direct action: voting and more conventional campaigning are essential, but NVDA can indicate a seriousness of commitment which elicits respect (it can also be self-indulgent, of course). No-one except possibly the participants were put at risk by the protest, while we are all being put at risk by the UK government and energy companies like E.on, which are pushing for a new programme of building coal-fired stations with only the paper-thin excuse they will be “CCS ready”.
How much risk are we willing to take with the lives of our children and their children? I’m 37 now. My sister is 27 and had her first child last week. My niece will hopefully be 70 in 2078. Her children could be 70 by 2105. What kind of world will we leave for them?
Then you had better have a serious look at peak oil. By the time your niece is 50 we will be a much less energy depleted world, according to the peak oilers. For example, at China’s current energy consumption rate of growth, within 15 years they will require all the world’s current production of oil — 86 million barrels per day, leaving nothing for everyone else. Watch the video series http://www.chrismartenson.com/peak_oil. Matt Simmons, who accepts AGW, says that peak oil is the far sooner and far worse risk than AGW.
Comment by Richard Wakefield — 12 Sep 2008 @ 1:56 PM
Richard C. wrote
Well, the field scientists share your concern. This is an interview, with reference to a 2005 paper.
…Many fiords, the channels carved by glaciers flowing into the sea, are deep with a shallow lip in front. Once the glacier floats off this shallow pinning point, it retreats into deeper water, making further disintegration likely. Reduced friction between ice and rock at the glacier bed can also increase glacier speed. Fiords often widen inland, causing the glacier to grate less heavily at the fiord walls and move faster as it retreats. And ice crystals in fast-moving glaciers can realign, further reducing friction, Howat said.
The Helheim glacier’s speedup has already propagated 12.5 miles up the glacier. The center of the Greenland ice sheet is only 150 miles inland, and the researchers worry that the effects of the glacier’s retreat will continue to move inland, ultimately decreasing the thickness of the whole ice sheet.
“If other glaciers in Greenland are responding like Helheim, it could easily cut in half the time it will take to destroy the Greenland ice sheet,” Howat said. “This is a process we thought was only happening in Antarctica, and now we’re seeing that it happens really fast in Greenland.”
As a reminder, this was the state of knowledge 75 years ago.
I’m wondering if any scientists have considered the following positive feedback factors in their climate prediction models.
Just as water absorbs more visible sunlight than land, and turns it into heat, water absorbs more than land, to various degrees. As sea levels rise, the ratio of water to land surface increases, thereby decreasing the albedo of the earth in general, I wonder by what percent. I’ve seen no mention of these factors.
Lennart (294 & 295) — The comments from J. Harper are about the paper which is the main topic of this thread. This paper appears to discount the possiblity of much contribution from WAIS; this seems sensible until the ozone hole closes. After that, possibly James Hansen is correct.
The is a bludgeonly simple way to remediate the problem; all it takes is about 1–2% of the world’s gross product, that’s $670–1340 billion per year. Just grow lots of biomass, use pyrolisys to produce biochar and sequester the biochar underground. If an average of 14 billion tonnes of carbon can be sequestered this way every year, in 100 years the CO2 concentration will be back to near an acceptable 280 ppm. (Obviously many variations on this idea are possible, and probably necessary due to peak oil and soon, peak coal.)
Comment by David B. Benson — 12 Sep 2008 @ 4:13 PM
> pyrolysis, biochar
I haven’t yet found a description of an actual built (or designed) processing station for doing this. Pointer welcome.
Each of these processing plants will be surrounded by… switchgrass. Millions of acres, altogether.
Close your eyes, and see it: hundreds of thousands of contiguous acres- of DRY grass. 8 feet tall.
It has to be big, mature, and dry- for any of the fantasy to work. It turns out that if you cut it when it’s green, you seriously weaken the roots- no crop next year. And if you cut it when it’s green- you’ll either have to use it right now, or spend energy drying it, so it won’t rot.
Are those huge fields of dry grass going to burn? Yes, they will…
Will such fields always burn? Of course not. Will they burn often enough to make the whole proposition uneconomic? YES.
but also note that torrification is a form of mild pyrolisys and searching on that term and also torrified wood will find many upon many references; there are at least three torrification reactors in The Netherlands producing torrified wood.
For slow (faster than mild) and fast pyrolysis, this review
I opine that Greenpa is a bit fixated on the fire problem; you and I have been through that before here on RealClimate. If an actual problem, grow something else other than switchgrass.
[Captcha chimbs in with "works consequences".]
Comment by David B. Benson — 12 Sep 2008 @ 5:33 PM
In December 1991 the top 10 metres fell of the summit of Mount Cook – the highest (3750m) peak of New Zealand. 10 million cubic metres of rock and ice slid into the valley. With the benefit of hind-sight it is likely that the peak was acting as a thermometer – detecting the mean temperature of the local environment.
As temperatures rose the tensile strength of the ice holding the peak together reduced to the point where it could no longer support its own weight – and off it came.
So even in 1991 the climate was changing the properties of alpine ice. Not necessarily melting it but definitely changing the way it behaves – its dynamics.
Its these sorts of changes which are in my view most likely to lead to an acceleration in ice sheet loss – shifting still frozen ice below the melt line unpredictably fast.
The persistent dislocate between global mean temperature and AGW forcings can only be the result of sinks like ice and water continuing to absorb energy. With every gram of ice that melts there is more energy to apply to the rest. So as the sinks go all the ‘in the pipeline’ temperature rise will come with a rush.
I would like to second Dan’s (#303) concern about whether potential feedbacks have been taken into account.
Besides the one he mentioned, what about changing albedo of the surface ice. Even small amounts of black soot and other dark particles on the surface and embedded in the ice will concentrate more and more over time on the surface as the ice around it melts. Higher concentrations of dark particles means faster melting which means yet higher concentrations of dark particles…
We see this process every spring in Minnesota until the last ice and snow is almost totally black on the surface. How much of a factor is this likely to be, and has it been factored into the calculations?
Also, with the loss of the overburden, the ground below will start to rise. Places that are now flat will become convex. Even a tiny change here could have large impacts. A marble on a flat table can remain stationary, but tilt the table even a tiny amount and the marble quickly rolls off. And of course this is a feed back too–the faster the overburden slides off, the faster the rise of the land below which further accelerates the slide….
And these rises don’t always happen gradually, but sometimes happen suddenly, essentially as earthquakes. Surely these would also hasten the collapse of the ice and the rates of flow to the sea.
I imagine that it would be difficult to model these, but if they are completely left out just because they are hard to model, wouldn’t that make the models quite consistently under-predict the rate of ice loss?
[Response: This is hard to model, but not impossible Hansen and Nazarenko (2004) made a first attempt and more sophisticated treatments are coming along as well. It remains to be seen whether current ice losses are related to that since black carbon in the northern mid-latitudes has decreased in recent decades (big increase in the tropics though). - gavin]
Wow, thanks for the fast reply. I’ll check out that ’04 article.
So are you admitting that most of the models are not accounting for such feedbacks and so we should not be so certain about a 2 meter limit by 2100?
As I was making my earlier post, it occurred to me that, though current black carbon deposits are important for getting the melt going now, what will really accelerate the feedback is the concentration levels of dark matter in the older ice as it melts.
So from what you said, I would expect a fair amount of acceleration from this source as melt reaches those sootier years, then dropping to not as much acceleration as it reaches ice from less-sooty pre-industrial times.
But I’m probably missing something obvious here.
While we’re on feedbacks, how worried should we be about recent reports of methane levels 1000 times background levels in parts of the Arctic Ocean. If the trigger has been pulled on the “clathrate gun,” are all bets off for rates of melt of the Greenland ice?
CALFED Delta contains all three kinds of projects at or below sea level. So what is the design life of a levee to protect threatened and endangered species? How much can we expect the sea level to rise within that design life?
I am afraid that we are going to spend $40 billion on engineering/construction using the IPCC SLR due to thermal expansion value, and in 20 years, the levees will wash out killing all the little critters and contaminating the drinking water sources for 20 million people with salt water. I hear from other sources that scoping studies for CALFED habitat protection work are being proposed based on the IPCC sea level rise from thermal expansion value.
Somebody (with the backing of a federal agency) needs to stand up and say, “Sea level rise will not exceed XXX meters under any conditions in the next 50 years. And, this is the value to use for critical engineering.” This one project gives having such a number a value of maybe $20 billion, right now. Add in the value of other costal infrastructure projects being currently planned; and, having a good number for SLR is currently probably worth a trillion dollars right now.
My guess is the IPCC understating SLR will cost the global economy trillions of dollars over the next 50 years. It is probably the single most expensive gloss ever made in any report, anywhere, anytime.
Wili (309) — The research in the paper which is the subject of this thread did not use GCMs. They used observed maximum rates to conclude that 2 meters in 2100 CE was the maximum they could foresee.
The paper does not appear to consider what will happen in Antarctica when the so-called ozone hole begins to close. I opine that greater ice losses will then occur.
Comment by David B. Benson — 14 Sep 2008 @ 7:42 PM
Aaron Lewis said: My guess is the IPCC understating SLR will cost the global economy trillions of dollars over the next 50 years. It is probably the single most expensive gloss ever made in any report, anywhere, anytime.
I have no idea what you are talking about. The IPCC specifically stated in the FAR that the sea level projections excluded dynamic ice-scheet processes. If you are saying that people have taken those figures to mean ALL potential rise, then that is their fault for not reading the report properly, and not that of the IPCC. No gloss.
Personally I think you will never find a scientist predicting 99.9999% certainty. Well, they could for an 80m rise! The new report (which is the theoretical subject of this thread) says 2m per century, but the discussion here reveals this is still a little tentative, as it is thought that geologically rises of up to 5m have been possible in a century (again, not certain though). The science is advancing as fast as possible… more time, money, resources will improve the accuracy of phenomenally complex problem analysis, but currently is looks like you are asking for absolute certainty (and 0.0001% counts as 0 in my book) where there is none.
re 295 Richard Wakefield “Does this take in account additions each winter?”
Yes; Howat et.al. are measuring ice mass balance, the difference between annual loss and accumulation. Also, if a volume of ice equal to that melted annually in the Arctic ocean melted from the Greenland ice sheet, very little of it would be replaced by snowfall (at current rates), and there isn’t underlying ocean water to re-freeze.
re 311 Hank Roberts – methane releases in the Arctic -
“At around 110 degrees easterly longitude, when we where wrestling with drift ice in western Laptev Sea, we discovered two new areas where methane concentrations in both the water and in the air above clearly exceeded the normal methane concentration in Arctic. A few days later a new area in the eastern Laptev Sea was discovered at 133 easterly longitudes.”
“Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated.”
The more I read about the intersection of climate science with public policy, the more I come to believe that:
1. instead of trusting the models we are instead going to perform the experiment.
2. ideological denialists won’t believe the results of the experiment either.
3. the fact that we don’t get a “do-over” if we don’t like the results isn’t fully appreciated.
The discussion on this thread is a perfect example. I am a layman, but I an incredibly confused as to how other climate scientists perceive his words on the subject. On the one hand, he is never directly contradicted, but on the other no-one really fully endorses his bold statements either. Given the stakes, I cannot work out if this is (frankly) cowardly timidity protecting scientific reputation, or if there is something genuinely wrong with either his method or logical deductions arising from the science.
1. As Lennary says in #294 (no inline response), Hansen asserts in the New Scientist article that as recently as “about 14,000 years ago, sea level rose approximately 20 metres in 400 years, or about 1 metre every 20 years.” This goes far beyond Gavin’s Hansen citation in the original article (although it doesn’t make a specific 2100 prediction, clearly it shows that it might be possible). Is this correct? Is it quite possibly correct?
2. Hansen specifically suggests in his Target Atmospheric CO2 paper that the maximum figure should be 350ppm. In Gavin’s Real Climate response (Target CO2) the figure of 350ppm was not even mentioned, despite this being the focus of the abstract – indeed Gavin concludes “So what does this mean for the future? In the short term, not much”. When I asked about this, (#18 in Target CO2), Gavin replied that “I don’t get hung up on a precise target”, but agreeing that CO2 levels need to be brought down as fast as possible. Surely policymakers need a target based on best-available science? Worse, many targets now are based on an apparently catastrophic 450ppm or even higher. Look at the supporters of the site http://www.350.org, meant to spread the word about 350ppm – hardly any major NGOs support it yet, let alone governments. If the figure is the best science we have, this must change urgently. Surely it is beholden on Real Climate contributors to unambiguously state – at the very least – the maximum level that can be thought of as having a reasonable probability of avoiding runaway climate change (based on best current knowledge, knowing it may be revised in future)?
3. Speaking of runaway climate change… no matter what the specific rate of SLR, Hansen et al write in the Target Atmospheric CO2 paper that “Continued growth of greenhouse gas emissions, for just another decade, practically eliminates the possibility of near-term return of atmospheric composition beneath the tipping level for catastrophic effects”. I can’t think of a more alarming sentence in all peer-reviewed science. Do Real Climate contributors agree with his words or not?
4. No-one has demonstrated that Hansen has received any practical support from his seemngly-lone campaign to get governments to agree to a 350ppm target. In New Sceintist, he writes “Reticence is fine for the IPCC. Individual scientists also can choose to stay within a comfort zone, and not worry that they may say something that proves to be slightly wrong. But perhaps we should consider our legacy from a broader perspective. Do we not know enough to say more? Using the fact that a glacier on Greenland slowed after speeding up as “proof” that reticence is appropriate is little different from the common misconception that a cold weather snap disproves global warming”. Is it not time that other climatologists join his attempts to convince governments, even if it is just to release specifically supportive statements?
I am a huge supporter of Real Climate, it is far and away the best resource we have for bringing scientists directly to the public. Frogive me if I have missed anything else that has already directly looked at this, but the James Hansen problem must be addressed urgently – in detail and at length.
Re # 313
I do not look for certainty, I look for rational risk management and economic analysis. And, Climate Science is being ever so reticent.
What SLR numbers made it into the IPCC FAR Summary for Policy Makers? What SLR number in any part of the IPCC FAR is of any use to an economist doing an analysis of the cost of global warming and the cost of curbing GHG emissions?
Engineers and economists ARE using the thermal expansion number. What are they supposed to use? The Thermal Expansion Number is the only number offered. I saw that number in a proposal going to BLM for CALFED Delta work. The organization that wrote that proposal is one of the smartest science and environmental consulting firms in the world. The Thermal Expansion Number is being used where it should not be used. Taxpayers are going to pay for this 3 times: once for doing the work with the wrong numbe; once for fixing the damage when it fails; and, once for doing it right.
IPCC should have given a probability distribution curve. That is, they should have said, “considering all factors our best guess is XXX meters by 2050 and YYY meters by 2100 with a 5% chance that it will be as low as QQQ meters and as high as ZZZ meter; and if you doing critical public safety engineering then use ###. All the IPCC AR4 said is that it will be more than AAA. The IPCC is a global organization and should consider the public safety of large human populations and endangered species around the world.
Pfeffer et al raises the bar, but still does not address all factors, and therefore should not be suggesting a total number, because that incomplete number is going to get used in engineering and economic analysis, and the resulting designs and analysis will be wrong. The error will propagate. The numbers in Pfeffer are not of a suitable quality for human safety engineering. If the Pfeffer values are going to be used, then a whopping big safety factor needs to be applied.
The IPCC passage (and sidebar) on sea level rise reminds me of Feynman’s comments about his Brazilian students. It is as if they have memorized every word of the science text, but have no concept of reality. IPCC was mostly written by scientists. When I look for literature on brittle compressive failure of ice, I find it was written by engineers. This is the failure mode that could move ice into the oceans rapidly, so why don’t I see any engineers in the IPCC author list?
The paper which is the main thrust of this thread indicates that such extreme changes in sea level are most, most unlikely thiis century. In particular, there are no large proglacial lakes to suddenly drain.
Next century? Well, that depends upon how fact Antarctica warms and the behavior of WAIS to the high sea level and great warmth. My understanding of Dr. Hansen’s warning is that, based on the paleorecord, with high levels of CO2 indeed Antarctic ice sheets will, over centuries, melt to a fraction of the current size.
Comment by David B. Benson — 15 Sep 2008 @ 4:26 PM
Aaron where do you come up with this stuff: brittle compressive failure of ice? Glacier ice failing due rain? This is not even close to the reality of glacier physics. You are not in a position of understanding glacier behavior well enough to comment on Pfeffer et al. work.
Here is a report of Professor John Schellnhuber, director of the Potsdam Institute for Climate Impact Research stating that “only a return to pre-industrial levels of CO2 would be enough to guarantee a safe future for the planet.”:
but I opine we had better start growing the trees now.
Comment by David B. Benson — 15 Sep 2008 @ 7:32 PM
Guy and Aaron, One can look at the science as a policy maker and ask 2 questions:
1) How bad will it get if CO2 gets to X ppmv (x=450, 500,…)?
2) How high can CO2 get before I have a high probability of serious consequences?
The models are not to the point where they can answer question 1 definitively–in part because we don’t know what tipping points we might encounter. To answer the latter question we can appeal to paleoclimate records and the remarkable stability of the last 10000 years and say 350 ppmv is probably safe. This is more an engineering answer, akin to how much weight a bridge can take.
These new results are very much consistent with Hansen’s concerns. The paper itself isn’t on-line as yet, although I assume it will be in a couple of days. The Mongabay article:
Earth already committed to 2.4-dgree C rise from climate change
Jeremy Hance, mongabay.com
September 15, 2008
Air pollution masking full impact of global warming
As of 2005 the Earth was already committed to rise of global mean temperatures by 2.4°C (4.3°F), concludes a new study published in the journal Proceedings of the National Academy of Sciences (PNAS). The conclusion is significant because the Intergovernmental Panel on Climate Change (IPCC) has warned that a rise in global temperature by 1 to 3°C will lead to catastrophic consequences, including “widespread loss of biodiversity, widespread deglaciation of the Greenland Ice Sheet, and a major reduction of area and volume of Hindu-Kush-Himalaya-Tibetan glaciers, which provide the head-waters for most major river systems of Asia.” These glaciers, predicted to shrink considerably in the next few decades, provide food and water to over two billion people.
V. Ramanathan and Y. Feng of the Scripps Institution of Oceanography at the University of California at San Diego argue that due to unique conditions in the Arctic, mean global temperature must be doubled to accurately reflect changes there. With a committed raise of nearly 5°C (9°F), the already diminishing sea-ice will continue to abate at alarming rates and the Greenland Ice Sheet may begin to crumble under climatic pressures. The researchers estimate the long-term exposure (thousands of years) of the Greenland Ice Sheet to a minimum warming between 1.9–4.6°C will lead to a complete melt of Greenland. Such a melt would raise sea levels by seven meters (23 feet).
Given the dire projections, Ramanathan and Feng warn that time is running out. Unless tough mitigation policies on greenhouse gases are put in place, the authors say the Earth will be locked into a rise of 3°C by 2030. They write that “CO2 mitigation polices are extremely critical if we want to limit further increases in the committed warming.”
Air pollution masking climate change
Ramanathan and Feng also explore a question often raised by skeptics: “Why hasn’t the planet yet felt the full force of climate change?” So far, the planet has experienced a mean warming of 0.76°C since the late 1800s.
The scientists conclude that a variety of factors are masking the full effect of climate change; one of the most significant of which is air pollution. Some types of air pollution send aerosols that reflect light like a mirror, brightening the planet and thereby cooling it. The pollutants ability to mask rising temperatures has been estimated at 47 percent. However, as nations clean up their skies, the masking effects of such pollutants disappear causing the Earth to undergo sudden warming. The researchers state that this relationship between dwindling air pollutants and higher temperatures can already be seen in Europe.
Considering the many negative aspects for health and environment of air pollution, the researchers do not recommend that nations should forgo policies that clean-up air pollution. But they say countries and international organizations should be aware of the potential rise in temperature due to such actions.
The authors suggest better models are needed to provide nations with more accurate predications of the relationship between air pollutants and greenhouse gases. “This is not easy and the costs may be substantial for developing such models and the associated observing systems, but,” the scientists conclude, “we do not have much choice.”
V. Ramanathan and Y. Feng (2008). On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead. PNAS Online Early Edition for the week of September 15-19, 2008.
Howat et al, Geophysical Research Letters, v35, L17505 (2008)
“Rates of southeast Greenland ice volume loss from combined ICESat and Aster observations”
estimate is 108 Km^3/yr ona average for the period 2002-2005, small glaciers melting much faster than the big ones
and this one was in the ‘in press’ section of the GRL
Wouters et al. “GRACE observes small-scale mass loss in Greenland”
this paper is very nice. i feel like singing
“Amazing GRACE, how sweet that data, for a wretch like me,
I was lost , but now am found, was blind, but now can see”
Table 2 gives the mass loss from 2003-2007 as 39,111,229,134,270 Gigaton
abstract sez 179+/-25Gt/yr corresponding to 0.5+/-0.1mm/yr sea level rise
1 1School of Environmental Science, University of Ulster, Coleraine BT52 1SA, UK (e-mail: firstname.lastname@example.org)
2 2Department of Earth Sciences, University of Maine, Orono, ME 04469-5790, USA
Deglacial sea-level records from NE Ireland between 21 and 11 cal. ka bp record marine transgressions and sensitive lithospheric responses to ice loading. The sawtooth sea-level curve contains four intervals characterized by: (1) strong net uplift, subaerial channelling and a global meltwater pulse (21–19 cal. ka bp); (2) ice loading, isostatic depression and high relative sea level (19–17.5 cal. ka bp); (3) ice loading, renewed isostatic depression and high relative sea level for >1000 years (17–14.5 cal. ka bp); (4) catastrophic ice wastage, rapid uplift and lowstand (14.5–13 cal. ka bp). Geophysical models do not capture these fluctuations.
Interesting batch of papers here, none of which I’d heard of. Google Scholar for a string for it to locate the link. It’s from a PDF titled:
SESSION NO. 42, 1:30 PM
Saturday, July 26, 2003
T13. Re-assessing the Role of Meltwater Processes
During Quaternary Glaciations (Posters)
(Commission on Glaciation)
Just one example, from p.3 — far more detail about how ice melts in bulk and causes floods, than I’d come across before, is common in these papers. And no doubt there’s more since this:
42-14 BTH 68 Kozlowski, Andrew L. 
THE ORIGIN OF THE CENTRAL KALAMAZOO RIVER VALLEY: RELATIONSHIPS BETWEEN OUTBURST FLOODS, TUNNEL CHANNELS, ICE DYNAMICS AND REGIONAL DRAINAGE HISTORY IN SOUTHWESTERN MICHIGAN
“… At the time of valley formation by the westward flowing outburst the Lake Michigan lobe had retreated at least 35 km to the west to the Lake Border moraine (14,000 ka B.P.) or possibly beyond. With the Lake Michigan lobe absent to impede flow path, drainage proceeded southwesterly until draining into Lake Chicago near St. Joseph, Michigan. The source of the outburst appears to have been a system of tunnel channels beneath the Saginaw lobe. Along the KRV, the meltwater flowed beyond the extent of the subglacial channels and became subaerial. Segments believed to be tunnel channels display convex-up flow paths and contain eskers ….
Thanks to so many of you for helpful links on these questions. From an abstract scan, it looks like MWP 1A is largely driven by Antarctica, with some additional rise attributed to the Laurentide and Fennoscandian ice sheets. According to Gavin’s summary above (again, I can only read the abstract), the recent paper limits Greenland alone to 2m, despite considering both Greenland and Antarctica… does this not mean that we still have a potential to hit this kind of level? I appreciate the lack of proglacial lakes, but can we be sure the Antarctica melt will be slow? Several people have commented on the effects of the closing ozone hole (imagine the ironic cry of the deniers…) and other processes (discussed in #316).
My basic layman’s logic is… if it has happened before, it can happen again. We have been surprised so many times by observation with regard to ice collapse…
The Guardian report in #321 doesn’t help the feeling of impending doom, especially the current projections from the Tyndall Centre of our eventual CO2 concentration levels… 650ppm! Even drastic action only gets us to 450ppm. Presumably (hopefully) this drastic action does not include Hanson’s ultra-drastic “leave fossil fuels in the ground” scenario, and the more I read the more that looks like sense.
However, there is still near-silence on this issue from Real Climate. I have asked from a response from the Real Climate contributors for a response to Hansen’s contentions five times now (in posts #180 #227 #249 #277 #315) over a period of 7 days, with a few supporting posts by others too. By nature I don’t buy conspiracy theories, but I am beginning to get a little suspicious here that at least there is an issue in academia that we mortals are not privvy too. I think (hope!) I’m asking genuine, reasonable questions… why do some respondants get rewarded by loads of answers to rude, ignorant questions while the elephant in the room keeps getting ignored?!
To be fair to Aaron, it’s perhaps a bit confusing that rain often gets mentioned in reports of melting glaciers. Aaron, the point is that if rain is falling on a glacier it’s a strong indication that the immediate environment is above freezing.
Re the idea of “brittle compressive failure” leading to a bulk loss of ice, I suspect you didn’t grow up in a cold climate. That’s not how melting ice behaves. Melting feeding back on itself and leading to a loss of structural integrity (calving, collapse due to undermining, etc.) is probably a better way to think of it. Consider what happened with the jokulhlaup decribed above.
Mauri, please don’t forget my question above about the possible implications of that jokulhlaup frictional melting for the Pfeffer et al results.
I also notice that there is a new GRL paper from Howat et al finding considerable inland thinning in southeast Greenland amd that the smaller glaciers are responsible for most of it. Both of those observations sound as if they may conflict with Pfeffer et al.
Small glaciers — not large — account for most of Greenland’s recent loss of ice, study shows
COLUMBUS, Ohio – The recent dramatic melting and breakup of a few huge Greenland glaciers have fueled public concerns over the impact of global climate change, but that isn’t the island’s biggest problem.
A new study shows that the dozens of much smaller outflow glaciers dotting Greenland’s coast together account for three times more loss from the island’s ice sheet than the amount coming from their huge relatives.
In a study just published in the journal Geophysical Research Letters, scientists at Ohio State University reported that nearly 75 percent of the loss of Greenland ice can be traced back to small coastal glaciers.
Ian Howat, an assistant professor of earth sciences and researcher with Ohio State’s Byrd Polar Research Center, said their discovery came through combining the best from two remote sensing techniques. It provides perhaps the best estimate so far of the loss to Greenland’s ice cap, he says.
Aside from Antarctica, Greenland has more ice than anywhere else on earth. The ice cap covers four-fifths of the island’s surface, is 1,491 miles (2,400 kilometers) long and 683 miles (1,100 kilometers) wide, and can reach 1.8 miles (3 kilometers) deep at its thickest point.
As global temperatures rise, coastal glaciers flow more quickly to the sea, with massive chunks breaking off at the margins and forming icebergs. And while some of the largest Greenland glaciers – such as the Jakobshavn and Petermann glaciers on the northern coast – are being closely monitored, most others are not.
Howat and his colleagues concentrated on the southeastern region of Greenland, an area covering about one-fifth of the island’s 656,373 square miles (1.7 million square kilometers). They found that while two of the largest glaciers in that area – Kangerdlugssuaq and Helheim – contribute more to the total ice loss than any other single glaciers, the 30 or so smaller glaciers there contributed 72 percent of the total ice lost.
“We were able to see for the first time that there is widespread thinning at the margin of the Greenland ice sheet throughout this region.
“We’re talking about the region that is within 62 miles (100 kilometers) from the ice edge. That whole area is thinning rapidly,” he said.
Howat says that all of the glaciers are changing within just a few years and that the accelerated loss just spreads up deeper into the ice sheet.
To reach their conclusions, the researchers turned to two ground-observing satellites. One of them, ICESAT (Ice, Cloud, and land Elevation Satellite), does a good job of gauging the ice over vast expanses which were mostly flat.
On the other hand, ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) does a better job at seeing changes at the steeper, less-flat margins of the ice sheet, Howat said.
“We simply merged those data sets to give us for the first time a picture of ice elevation change – the rate at which the ice is either going up or down – at a very high (656-foot or 200-meter) resolution.
“They are a perfect match for each other,” Howat said.
“What we found is the entire strip of ice over the southeast margin, all of these glaciers, accelerated and they are just pulling the entire ice sheet with it,” he said.
Howat said that their results show that such new findings don’t necessarily require new types of satellites. “These aren’t very advanced techniques or satellites. Our work shows that by combining satellite data in the right way, we can get a much better picture of what’s going on,” Howat said.
Mauri, visiting Howat’s web page I noticed this related in-press paper. Title/abstract:
Synchronous retreat and acceleration of southeast Greenland outlet glaciers 2000–06: ice dynamics and coupling to climate
A large portion of the recent increase in the rate of mass loss from the Greenland ice sheet is from increased outlet glacier discharge along its southeastern margin. While previous investigations of the region’s two largest glaciers suggest that acceleration is a dynamic response to thinning and retreat of the calving front, it is unknown whether this mechanism can explain regional acceleration and what forcing is responsible for initiating rapid thinning and retreat. We examine seasonal and interannual changes in ice-front position, surface elevation and low-speed for 32 glaciers along the southeastern coast between 2000 and 2006. While substantial seasonality in front position and speed are apparent, nearly all the observed glaciers show net retreat, thinning and acceleration, with speedup corresponding to retreat. The ratio of retreat to the along-flow stress-coupling length is proportional to the relative increase in speed, consistent with typical ice flow and sliding laws. This affirms that speedup results from loss of resistive stress at the front during retreat, which leads to along-flow stress transfer. Large retreats were often preceded by the formation of a flat or reverse-sloped surface near the front, indicating that subsequent retreats were influenced by the reversed bed slope. Many retreats began with an increase in thinning rates near the front in the summer of 2003, a year of record high coastal-air and sea-surface temperatures. This anomaly was driven in part by recent warming, suggesting that episodes of speedup and retreat may become more common in a warmer climate.
Steve: I have tried to avoid the Howat paper which I have reviewed. A post has been submitted to Gavin on this topic exploring this paper. It notes that the thinning and acceleration is mainly associated with marine terminating outlet glaciers, and the cause of the acceleration is you guessed it, not more meltwater delivery to the base. I do not find the Pfeffer paper very important overall, it does not advance our understanding of the ice sheets behavior. It merely applies some of our understanding to setting realistic bounds on sea level rise. The Howat paper and several other recent papers are far more important, if less interesting to the media.
Guy, read a bit more and put the pieces together; nobody’s ignoring what you keep asking, it’s all being discussed right here, right now, as fast as people can do it. People have day jobs; people have to read actual references, not newspaper articles, and think before commenting in their own areas of expertise, and may well be writing papers instead of blogging on the most important questions. That’s how it works.
So if I understand correctly Pfeffer e.a. do not take alle possible (feedback) mechanisms into account which could possibly cause the ice of GIS and WAIS to melt faster than currently projected? Peter Cox e.a., for example, think carbon cycle feedbacks may cause substantial additional warming: http://www.naturalnews.com/022481.html
He called for 80% cuts in 2050 relative to 1990, which would be about 85% cuts relative to 2000, which is also the upper limit in IPCC’s AR4, Synthesis Report, Table SPM.6; still not enough though to have a good chance of limiting warming to less than 2 centigrade, it seems: http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf
The strongest cases I’ve seen so far for 100% cuts by 2050 have been made by Spratt and Sutton in Climate Code Red (based on Hansen, but also on someone like Ken Caldeira): http://www.climatecodered.net/
So are we prepared for a global mobilization compared to the World War II mobilizations? How many RC-contributors would support such a mobilization? Nicholas Stern (almost) seems to realize this is what’s necessary, but he also seems to think it’s politically not feasible, so he’s a little more diplomatic about it. Even environmental organizations seem to be reticent to not scare politicians and general public too much (see also Climate Code Red). So me too is very curious how the people of RC think about all this. Are Hansen, Schellnhuber and others too worried or not?
may be behind a paywall for interested readers. Here are relevant quotations from the conclusions:
“2. Initial retreat of the WAIS appears to have occurred between 15,000 and 12,000 yr and continues into the Holocene. There was significant retreat of the ice sheet in the Ross Sea, and possibly Weddell Sea, after 7000 yr BP.
3. During at least the final stages of the glacial maximum, the expanded WAIS was flowing across an extensive deforming bed. This implies gentle profiles, high rates of flow and discharge, and possibly rapid retreat. Thus, the LGM configuration may have changed during the LGM.”
“5. The Antarctic Peninsula housed much greater volumes of ice during the LGM than was previously thought, and therefore made a greater contribution to the post-glacial sea-level rise.”
Figure 13 indicates that Antarctic Peninsula ice retreat began 14–12 kybp, depending upon location.
Comment by David B. Benson — 16 Sep 2008 @ 6:36 PM
Re #330: Guy, perhaps it’s because I’ve been following this stuff longer than you, but I have to say that I don’t think Hansen feels (or has a reason to feel) unsupported by other scientists. It seems clear that he’s on a campaign to get more scientists to speak out, and I would say there’s evidence of considerable progress along those lines. Certainly there are many scientists who don’t feel comfortable with taking on such a role or even with seeing others do so, but I don’t take that as any particular reflection on Hansen.
Re this site’s coverage of Hansen’s work, bearing in mind that his views and results already get more of a public airing than those of any other climate scientist and that the limited time of the RC authors means that plenty of deserving topics never get written about at all, I see no particular need to change things. Also, in case you don’t know this, Hansen is also Gavin’s boss, which relationship would tend to reduce the effectiveness of any posts lauding the former’s work. Finally, if you search around the climate scientist blogosphere you’ll notice no lack of nice things being said about Hansen.
Re #334: Thanks, Mauri, I’ll look forward to seeing that.
Just one specific two-part question about the jokulhlaup frictional melting if you don’t mind: Was the potential scale of this effect known about before this observation, and is there any major implication for modeling ice sheet behavior? Of course I’m happy to wait for the answer if this will be addressed in the forthcoming post.
Glaciology: Lubricating lakes
More than 150 subglacial lakes have been discovered beneath the Antarctic ice sheet. The four most recent additions, found right at the start of fast flow in a large ice stream, suggest that the lakes influence ice dynamics.
Antarctica is well known as the coldest place on Earth, but it is also surprisingly wet. Whereas the upper part of the ice is cold, geothermal heat and the insulating effect of the overlying ice combine towards its base to bring extensive areas of ice at the bed to its melting point.
Thanx for the pointer to an excellent paper. I have heard about Niagra Falls eroding many feet in a single day, long ago. Is it possible that glaciers can enlarge their exits to the ocean through erosion ?
Thanks again for eveyone’s input, I really do appreciate it!
#336 – I was referring to the discussed paper here – http://www.sciencemag.org/cgi/content/abstract/299/5613/1709?siteid=sci&ijkey=1Y7ijVfKZOpRU&kytype=ref. “With the use of a climate model of intermediate complexity, we demonstrate that with mwp-1A originating from the Antarctic Ice Sheet, consistent with recent sea-level fingerprinting inferences, the strength of North Atlantic Deep Water (NADW) formation increases, thereby warming the North Atlantic region and providing an explanation for the onset of the Bølling-Allerød warm interval.” (ps – thanks for the #337 ref, David)
#335 – I know, I feel quite bad about repeatedly asking for clarification of busy, working scientists. However, since I first asked over a week ago there have been a great many replies since then on other subjects, some of which seem like pure distractions. And as shown most fully in #315, these are really fundamental questions that I cannot see Real Climate’s stance meshing well with that of Hansen’s – in this very thread they seem quite at variance. Maybe I have missed something, but I’d love to be shown what!
The target 350ppm figure seems utterly crucial to me. This is what Hansen is proposing to world leaders, and being widely reported in the media. It is the basis of Hansen’s April paper, which Real Climate has discussed… but with no mention of that target. I need to know if this figure is supported by others – not just as a “safety first” figure, but as a reasonable maximum figure. Policymakers are still gunning for 450ppm… is this a recipe for disaster or not? From Real Climate at the moment, I still have no idea. If anyone else has any specific pointers to RC utterances on the subject, please let me know!
I think the point being made by Guy and Aaron (315, 316) is that we need some form of risk based best guess on which we can make planning decisions.
As they point out, the current engineering and regulator community are using the IPCC numbers (in some cases modified a bit by recent research). For example, currently, Australian regulators are using 0.91m as the 2100 year number! This is less than half of the 2m being discussed here.
268 gets the point. Engineers need a reliable estimate for safety. Planning has to be approached in a similar manner. Eg, different design events are used for different risk structures — ‘normal’ buildings are designed for 0.002 annual probability of exceedance, while ‘post-disaster recovery’ buildings (such as hospitals, major bridges) are designed for 0.0004 (1 in 2500).
If scientists (like RC) cannot give us an up to date re-assessment of SLR (say on a 6 monthly basis with an added factor to account for uncertainty) for use in planning, then as has been pointed out above, billions of $ will be spent on projects that will be drowned.
Will no-one state their best guess SLR by 2050/2100 and add a factor for uncertainty?
David Benson (#336): I think one could reasonably argue for levels as high as maybe 330 ppmv, but no higher as an “engineering” level. It is a moot point, as I see little hope of holding things below 450-500 ppmv.
#336 (Lennart)”So are we prepared for a global mobilization compared to the World War II mobilizations?”
That’s certainly what’s needed – only for decades rather than years, and without an enemy to focus on. Not easy to imagine. Which is why I’m hoping for nature to put on a series of showy (but minimally destructive) demonstrations that the problem can’t be ignored, or postponed for the next government to deal with.
> If scientists (like RC) cannot give us an up to date re-assessment
> of SLR (say on a 6 monthly basis … then … billions of $ will
> be spent on projects that will be drowned.
But only dollars, not euros or other currencies, to the extent the precautionary principle is applied. It is applied except in the US for most purposes these days, and increasingly so.
ReCaptcha: Great MARKETS
I swear that AI seems to be waving hands and saying “pick me” …
Guy (345) & Ricki (347) — Amateurs rush in where experts fear to tread.
So I’ll rush in. First of all, the Pfeffer et al. paper makes clear that they find 80 cm in 2100 CE most likely; 2 meters is simply an almost risk-free upper bound. So simply double these for 2200 CE except that this does not take into account the possibilty of WAIS melting more in that next century.
As for MWP 1A rapid surge and the prior, similar rise around 19,000 ybp, it does seem that Antarctica was a major participent. However, with the sea lowstand of about 135 m below present, the Antarctic Pennisula ice sheet extended all the way to the outer edge of the continental shelf; that’s a considerable mass of ice on a fairly gentle slope (which becomes even more gentle at the inner edge of the continental shelf). I opine this meant tidewatr conditions over areas much more extensive than at present. Put another way, the ice in Antarctica is now essentially up into the mountains (except for part of WAIS). Given the steep slopes, each meter rise in sea level exposes little ice to tidewater conditions. My amateur conclusion is that a repeat of MWP 1A is not possible under current condtions.
However, you might care to look for papers which consider the stability of WAIS.
Ray Ladbury (347) — At 330 ppm Greenland will slowly waste away. Holding the increase to 450 ppm is going to be tough to do; even tougher may be convincing everybody to begin sequestering carbon to bring the level back down in about a century.
Comment by David B. Benson — 17 Sep 2008 @ 4:09 PM
But it seems that the continental shelf to the east of Tierra del Fuego was ice-free during LGM:
Comment by David B. Benson — 17 Sep 2008 @ 5:33 PM
David Benson: “At 330 ppm Greenland will slowly waste away.” I’ll take slowly, especially since it might give us time to adapt. What really concerns me is the probability that we could trigger a massive “natural” ghg release and render any mitigation moot. I think that at 330 ppmv, that probability is small. Of course 280-300 is more desirable, but I don’t see people rushing to sign up for that goal.
David, where on earth do you get the assumption that you can just double the SLR of 2100 to get the SLR for 2200? This is the kind of nonsense that leads to real disaster. And you are totally ignoring the effect of sea level rise on the WAISDce shelves.
Comment by David B. Benson — 17 Sep 2008 @ 7:15 PM
Thanks David (349). I appreciate your effort to make a stand.
Would all of the RC scientists also feel confident taking 2m for 2100 to be a prudent upper limit without adding further ‘uncertainty’ factors? Imagine the siting of major highways or rail or a new suburb.
What I am trying to get a handle on is how to approach planning for development as opposed to building of single buildings.
For example, if an existing suburb was sited in an area say 2 to 4m above sea level where the setback was some distance from the shore (to avoid coastal erosion) should new houses be allowed? (Scenario A)
The other side of the coin is to say, for the same location, if there was no suburb already there, should a new suburb be allowed? (Scenario B)
So if 2m was to be taken as the 2100 target, new houses might be OK for an existing suburb as they may be expected to last well into the next century. Whereas, a new suburb should not be allowed as it would be in the wrong place for the longer term.
I despair. What is the science-based target now?!!! Lennart’s excellent post on #336 cites other papers saying 450ppm is far too dangerous a target. And, once again, Real Climate contributors are totally silent.
I am trying to get a UK-baesd initiative off the ground, but at the moment do not have a target of any kind I am comfortable with a) working and b) getting widespread scientific support. What hope of any action – anywhere – without one? At this point, it really is no use citing the IPCC reports when so many climate scientits (including a very public, very vocal and very qualified Hansen) suggest that these targets will do no good whatsoever. I’m not concerned about what is politically acheivable yet – I need to know where we can aim first, and then figure out if we have any chance of getting there afterwards (though I am aware that Hansen says 350ppm is definitely do-able). Any other method of proceeding seems irrational to me.
What does it take to get an RC response to this? So many other responsants have been helpful, but we really need something meaty directly from the experts in the field. This is now my 7th attempting at getting a response over 9 days – not even a “we’re working on it”, a link to a previous response or a reason why there hasn’t been a response. Help! Don’t you understand why this target is so important?! Or if it is unimportant, or totally un-knowable, please explain why!
Ron Taylor (353) — Pfeffer et al. consider WAIS to be stable (at least up until 2100 CE). So until somebody finds a paper suggesting otherwise, 2 meters, possible up to 4 meters by 2200 CE seems to account for potential WAIS melt.
Ricki (355) — Planning for how far in the future? If we don’t reverse the growth of CO2, the sea level will continue to rise for many, many centuries.
Guy (358) — Joe Romm (ClimateProgress; physics PhD) is pushing for 420 ppm, tops. As you know Jim Hansen has proposed ‘less than 350 ppm’. I agree with both, but go further in stating than the sooner we get back to about 290 ppm, the better.
sidd (357) — Thank you for the link to the map and I stand corrected. However, EAIS is certainly going to remain stable, at least for a long time. The part of WAIS grounded below sea level is potentially worrisome.
Comment by David B. Benson — 18 Sep 2008 @ 4:50 PM
Thanks for all of the comments and Real Climate’s patience, justice, and fortitude in allowing me to post my points.
The problem is that most people thinking about the behavior of the GIS have assumed substantial sea ice, and therefore a cold, dry Arctic. Based on water temperature changes detected by buoys, in Feb., 2002 I predicted a sudden and rapid decline in Arctic Sea Ice. These predictions were ridiculed. I understand and accept ridicule. Nevertheless, for the last 5 years, I have been thinking of the implications of a warmer, moister Arctic that has less sea ice, and therefore absorbs more solar radiation.
Bindschadler et seq. (http://yosemite.epa.gov/oar/globalwarming.nsf/content/ResourceCenterPublicationsProbability.html ) do not address how the strength of ice varies with temperature, nor do they address any possibility of an ice free Arctic ocean as a source of latent heat. The combination of (latent) heat from the Arctic/North Atlantic and the non-linear function of ice strength with respect to temperature means that GIS collapse is possibly enormously more rapid that anything considered by Bindschadler et seq.
We can project loss of sea ice, and resulting available latent heat. Any good engineering library has resources with equations of ice strength under various conditions that can be solved by any student with a computer. So, it is not reasonable to say that this is beyond science. It may not be a calculation that has been published. It may not be a calculation that some science agency manager wants to see published, but it is not beyond science. This is the Lake Missoula Model, (a watershed dammed by ice) and that is science. The result is the flow of a mix of solid ice and water into the ocean at high rates of speed. Such flows can scour any gap they need through any type of rock – in a few hours. The real question is, “Do you accept the possibility of an ice free Arctic Ocean in the near future?” An ice free Arctic Ocean has implications.
The assumption that summit ice will be protected from the warmth at lower altitudes is also not correct. We have that assumption because the summit ice that we normally see sits on rock (i.e., the glaciers in the Alps, Cascades, & etc.). However, in Greenland, the ice massifs are supported by ice, not rock. Latent heat can/will eat the GIS from the bottom up.
How likely is this concept of high speed water/ ice flows? Get out your geologist alter ego and go look at places where we know ice sheets retreated. Many of these locations have evidence of high speed, high volume ice/water flows. That makes me think that my physics is correct. I do not appeal to authority or citations, because I cannot find any peer reviewed literature that is contemporaneous with previous ice sheet retreats.
Of course the storm surge, tide, wave action, etc would have to be taken into account. This adds a bit of complexity, but is in any case regularly assessed by coastal engineers.
The increase in storm intensity is less predictable than general sea level rise as there may be local and regional climate effects. In any case I believe this to be a lesser effect than the rise itself as the coastal erosion will be driven by the SLR even though the erosion will largly take place during storm events.
On the issue of how far ahead we look — I do not think we can look further than 100 to 150 years as far as infrastructure planning is concerned except that caution should be exercised for extremem hazard situations such as nuclear plants. These are generally dealt with by regulators on a case by case basis anyway.
For normal infrastructure planning, structures will be expected to last for 70 to 120 years before we replace them. Also, in the next 20 years it will become clear both how big the climate change impact will indeed be and how much effort the human race is willing (or able) to expend to counter it.
Therefore, we can limit ourselves to planning for the next 100 to 150 years for the time being.
over yours to obtain some confidence about what parts of the Antarctic ice sheets have tidewater terminations.
Comment by David B. Benson — 19 Sep 2008 @ 6:56 PM
For those interested in considerable detail:
Climate and Sea Level Change: Observations, Projections and Implications
By R. A. Warrick, E. M. Barrow, T. M. L. Wigley
Published by Cambridge University Press, 1993
ISBN 052139516X, 9780521395168
Comment by David B. Benson — 19 Sep 2008 @ 7:30 PM
some information about antarctic and greenland glaciers, with maps of elevation changes and marine glaciers may be found here:
Shepherd and Wingham, “Recent Sea-Level Contributions of the Antarctic and Greenland Ice Sheets” (2007), Science, v315, pp1529-1532
takes you to several excellant graphics for understanding Antarctic bedrock elevations and ice thicknesses.
Comment by David B. Benson — 19 Sep 2008 @ 10:06 PM
OK… I gave up reading them all in the 200s…
1. Richard C ain’t me (and our names are backwards, I’m more spacey!) And Richard Wakefield… please try to live up to your Richardness. Your deliberate suppression of any logical talent you might have embarrasses your fellow Richards. I’ll dedicate this post to you, in the hope that you’ll take off those blinders:
The two ice sheets in question, Greenland and WAIS, share common features – they are way below sea level and bowl shaped. They got that way to a certain extent by their very mass. The “pry” verb Peter is questioning is about tides and only applies at the grounding line. In fact, we can (mostly) ignore everything except the grounding line. Beyond it, it’s just floating ice. Twice a day the grounding line moves. Tide comes in, the ice lifts, and the grounding line retreats. Tide goes out, the grounding line advances. Beyond the grounding line, ice randomly breaks off, floats towards the equator, and melts. Everything beyond the grounding line is secondary – it affects flow, but flow might actually slow the retreat! Yep, it looks bad on the surface, but for t+50y, it’s a different story, since the ONLY important result is grounding line advance or retreat and increased flow tends to advance the grounding line. Kind of like La Nina – which warms the planet by cooling the surface – the cooler the surface, the more radiation imbalance there is and the faster the planet warms! That we live at the surface/atmosphere boundary is just anthro-bias. Ask a deep water fish whether La Nina is a warming or cooling event.
Since the ice sheet is bowl-shaped, the grounding line by definition is the lowest part of the system. Thus, the heaviest water will travel there. Meltwater is salt-free, and so light, while warmer seawater will displace it. The meltwater will travel outward, until it freezes. Thus, the edges of the ice shelf are thicker than the grounded edge. So we have a thermohaline pump, with heat from the ocean eating the grounding line competing with the ice flow from the centre of the ice sheet. In WAIS, the ocean is “winning” at a rate of 120 metres per year. Since the distance between Ross and Ronne is about 1000 km, 1000/.24 = 4000 years to complete instability. Add in any sort of acceleration factor, and a few centuries becomes the best estimate. Greenland is NO different from WAIS except it is in a warmer environment and has significantly better mountain protection – almost 360 degrees. But once the grounding line get past the mountains, Greenland’s situation deteriorates phenomenally. The Gulf Stream’s NW offshoots will infiltrate southeastern Greenland (note the GRACE ice loss maps), break off icebergs, and flush them to the tropics. There, they will cool the surface, which, as per La Nina, will warm the planetary system by increasing radiative imbalance. GIS has less than 100 years of life left. Folks laughed when I said ice-free Arctic Ocean in 2020. Seems I was a tad optimistic 15 years ago. I’m probably optimistic when I say ice-free Greenland Sea in 2100. The key thought-process is that ice is *there* or *not* at a single temperature, and ocean currents are big. Look at Sidd’s map of Greenland: http://membrane.com/sidd/greenland.html
Once currents can travel between the two big mountain passes in southern Greenland, it’s game over.
Your statement of a 30C°/3km lapse rate in Greenland seems confused. The dry rate is 10C°/km but the average environmental lapse rate is closer to 6.5C°/km. Your point, however, is well taken
You’re right that the mean tropospheric lapse rate is about 6.5 K/km, but that’s a global average, and depends on the water vapor cycle and the release of latent heat. Greenland may be cold enough that there’s very little water vapor above it (cf the Clausius-Clapeyron law), and thus the lapse rate may be closer to the adiabatic 9.77 K/km.
Aaron, just for chuckles, the Telegraph article commits the classical blooper of converting 4 degrees C temperature rise to 39.2 degrees F… “according to scientists”. Yeah, sure ;-)
Comment by Martin Vermeer — 23 Sep 2008 @ 12:09 PM
#371 Aaron. Yes it’s real science – see #314. My layperson opinion is that it probably only relevant to Greenland melting in the context of additional total global warming, since greenhouse gases are relatively well mixed over short time constants in the atmosphere and between N & S hemispheres; although, a continuous and large release over a summer could boost CH4 concentrations and greenhouse effect in the northern hemisphere.
371 Aaron, it’s just an expected carbon feedback which means that unless we can get to 350ppm (or 300) by a few years ago, staying below 1000 (CO2 equivalent) will be durn difficult. This means that slowing human CO2 emissions is now silly, as 2ppm isn’t squat in the new world. Take a match and light the straw in a barn, then try using a squirt gun to put it out. Woulda worked for the match… None of this is news. Permafrost temperatures have been tracked for a long time. They’re about to go above 0C in large swaths of Alaska and Siberia. Arctic ocean temps have been studiously recorded. “Gee, it’s getting rather warm.” Clathrates form to the extent current temperature allows, and melt from the bottom up as things warm. The melted clathrate expands ~160 times in volume, so pressure builds up, the thinning clathrates above break, and a huge natural gas leak forms. (Though pressure release drops temperatures, so the leaks can re-seal if not too bad.) Again, not even close to news. We KNEW all this many years ago.
The Deniers are now right, even though they are totally wrong. It is silly to reduce CO2 emissions since building levees and dikes and moving ports and cities takes concrete and lots of fossil fuel. We might as well emit the CO2 and save a couple billion lives instead of the 500 million predicted by Lovelock. Letting folks divert it to Monster SUV or military use isn’t wise, though.
Notice that the melt zones on Greenland now stretch from coast to coast, and center on the two big gaps in the mountains. Soon, the oceans will invade, burrow through the sheet and start flushing. I bet Pfeiffer et al didn’t count on Siberia joining the game, so they got crap results. (If I’m wrong, let me know) When one considers the ENTIRE system, instead of just one’s own tiny specialty, then completely different results appear. Since it takes a couple years to come up with results, folks doing the science use outdated assumptions with regard to systemic conditions. So the game of catch-up for related disciplines never gets better. (Though they do their best. This isn’t an insult, just a condition resulting from the tremendous pace in change of climate and knowledge thereof)
The alternative is to start brimstoning the atmosphere, but Russia disagrees, and has nukes and an attitude.
This map shows a very extensive undersea permafrost in the Arctic ocean covering almost all the shallow continental shelves. I believe it is there since the last ice age – but how come it has been maintained for so long? Can that be just because of an extraordinarily slow response, or is there some process maintaining it? How would that process be changing now?
Richard C., Actually, there is every reason still to try and hold CO2 as low as possible. Even if (and it is still if) we can’t keep things from getting bad, it is quite another thing to contend that we can’t make them worse. We will do much better at both mitigation and remediation if we keep the changes from occurring rapidly on a human scale.
376 Pekka, grand map. The sea north of Siberia used to be covered with ice. Now it’s ice-free, and the ocean is only 10 to 25 metres deep http://mappery.com/map-name/Arctic-Ocean-Bathymetric-Map The rivers have increased their flow, too. Clathrates are only stable as long as the regime doesn’t change. If one assumes that Mann’s hockey stick is anywhere accurate, then any clathrates that would have released would probably have done so long ago. (They probably did!) Those that survived up until now were stable at Hockey shaft conditions. But since Siberia and the Arctic Ocean have warmed tremendously, the zone of stability has shifted. Everything outside the new zone will thaw and release. That will further warm the planet, and so the arctic, which will further destabilize clathrates. We’re just along for the ride…
http://nsidc.org/images/arcticseaicenews/20080924_Figure3.jpg Another good map, which compares the health of the arctic ice cap between 2007 and 2008. As you can see, much of the ice in 2008 is first year ice (age is a good proxy for thickness and strength). First year ice is full of salt and so especially weak. Instead of the small recovery extent suggests, 2008 is significantly worse than 2007, and it sets up a catastrophic 2009.
3rd series of attempts to post this … Captchad! (Sounds like a Florida election official) This one has to work, Captcha: Estimate kindled
73 Aaron asked, “The question stands. What is the value for SLR that you are 99.9999% sure will not be exceeded in the next 100 years?” 6 metres for GIS, 6 metres for WAIS, 10 metres for EAIS, and 2 metres for thermal expansion and glaciers and fudge. Then the converse, 0.4 metre for GIS, 0.4 metre for WAIS, -0.3 for EAIS and fudge. So, 0.5 metre
[Response: Are you using a < symbol? use the html instead < - gavin]
Thanks, Gavin… So, 0.5 metre < rise by 2108 < 24 metres. (Unless mankind does something to change the game, of course.)
88 Iblis, I did a quick guesstimate of the major depression volume, and it was a piddly 5cm of sea level mitigation or so. (Don’t quote me!)
181 Bruce – Yep, the difference in CO2 levels between the Eemian and today is key, since increased CO2 increases polar temps, so it takes a lower global temperature to affect polar ice (though the estimates of Eemian temperatures could be in error for exactly the same reason). Add in the much higher CH4 levels today, and the Eemian isn’t so grand a model.
377 Ray, we’ll know pretty soon. If human emissions get dwarfed, then it’s a new ball game. Yep, keeping CO2 as low as practical would still be right, but the CO2 still needs to be spewed. Moving people out of harm’s way takes a lot of energy, and the only developed energy source we have is carbon. It will take every bit we’ve got and more, so burning dinosaurs even harder will be needed, unless we’re willing to do extensive triage and write off quite a few billion people. If this does come to pass, it will test the US’s adherence to their core concept, that “All humans are created equal.” Is it Animal Farm? “But some humans are more equal than others.”
Yep, I used the word “now” in a deliberately vague and somewhat wrong context for emphasis and was tongue-in-cheek too (even said Deniers were RIGHT!). So knowing the methane data that has just come in, what is a good guesstimate on the odds that we’ve already initiated a methane release which will ramp up enough to take us over the edge regardless of any reasonable CO2 emissions scenario? I’d say 80%.
This was released yesterday about the Wouters et al., GRL paper (‘GRACE observes small-scale mass loss in Greenland’). Basically their findings are that Greenland currently accounts for 0.5 mm/yr sea level rise. Their seems to be a speed up in the last few years too (record loss in 2007), although the authors mention that more observations are necessary to come to reliable predictions for the future:
An accurate picture of ice loss in Greenland
Resarchers from TU Delft joined forces with the Center for Space Research (CSR) in Austin, Texas, USA, to develop a method for creating an accurate picture of Greenland’s shrinking ice cap. On the strength of this method, it is now estimated that Greenland is accountable for a half millimetre-rise in the global sea level per year. These findings will be published in the scientific journal Geophysical Research Letters in early October.
The research was based on data from the German-American GRACE (Gravity Recovery and Climate Experiment) satellites, two satellites that have been orbiting the earth behind each other since mid-2002. Deviations in the earth’s gravitational field cause fluctuations in the distance between the satellites, which is measured to a precision of a millionth of a metre. As gravity is directly related to mass, these data can be used to plot changes in the earth’s water balance, such as the disappearance of the ice caps. Satellite data of this kind are ideal for measuring areas such as Greenland, where the extreme conditions make local measurements very difficult. With this in mind, researchers from TU Delft and the CSR devised a method that would create a more accurate picture of the changes taking place in Greenland than had previously been possible.
Sea level rise
Greenland lost an average of 195 cubic kilometres of ice per year between 2003 and 2008, which is enough to cause an annual increase in the global sea level of half a millimetre, or 5 cm over the course of the next century. A report recently published by the Dutch Delta commission estimated that the melting ice cap in Greenland would cause the sea level to rise by 13 to 22 cm by 2100. But these two figures do not necessarily contradict each other: whereas the first two years of the study showed a loss of 131 cubic kilometres of ice per year, during the last two years this figure had risen to 222 cubic kilometres per year, an increase of 70 percent. This sharp increase was mainly caused by the extremely warm summer of 2007, when more than 350 cubic metres of ice melted in just two months. However, it is not yet clear whether the ice will continue to melt at this rate during the next few years, as ice loss varies greatly from summer to summer. Long-term observations are needed to compile a reliable estimate of Greenland’s contribution to the rising sea level during the next century.
The method used also enables scientists to plot the loss of mass per region, thereby providing new insight into the patterns of ice loss. For example, for the first time since measurements were started, the extremely warm summer of 2007 saw a decrease in the ice mass at high altitudes (above 2,000 metres). It also became clear that the ice loss is advancing towards the North of Greenland, particularly on the west coast. The areas around Greenland, particularly Iceland, Spitsbergen and the northern islands of Canada, seem to be particularly badly affected. A follow-up study will focus on the influence of these smaller glaciers on the sea level.
361 Aaron, grand post. Note that Greenland’s hip, from the bay near Tasiilaq to the Jakobshavn at Ilulissat, is under 600km wide. The “eating from the bottom up” of ice you mentioned will focus there. Lower ice gets eaten by the ocean and warm moist air, and higher ice either fractures and dumps, or flows into the terminus. This temporarily helps replace or protect the low ice from further erosion. Since the base of the sheet is far underwater, it’s a wet-melt system. Exponential melt is likely once the triple-whammy of an ice-free arctic ocean (can you imagine what the summer rainfall will be in Greenland?), increased ocean temperature, and melting past the mountain passes occurs. Tides will work to clean-up ice debris at the passes between the mountains, such as at Jakobshavn and Tasiilaq, so ice flow will be fastest there, and the ice will slump. This will attract melt and rainwater on the surface, and moulins below. Combine the three forces and a groove will begin to show, getting deeper and more fragile until the smallest of paths is cut through Greenland’s hip and melt-rate becomes essentially unlimited as currents replace tides and outflow as the clean-up crew. That’s 2×300 km to 6 metres of sea level rise.
Hi Andrew , i dont know if you are aware of the palma volcano that is just off of the west african coast ?
A snipet …..
NARRATOR: The big question is where and when the next large volcanic island collapse will occur. Because these landslides all happened in the ancient past no-one has ever witnessed one. They are so rare scientists cannot be sure what the precursors will be, but of all the large volcanic islands around the world one in particular shows disturbing signs of instability. If this island collapses it would create a mega-tsunami that would race across the Atlantic and hit the east coast of the United States. Every city on the shoreline would be destroyed. From New York in the north to Miami in the south. The wave would wreak havoc for as much as 20 kilometres inland. The origin of this wave would be thousands of miles away. This mega-tsunami would come from a volcanic island off the coast of North Africa, from one of the Canary Islands. It would come from the island of La Palma. La Palma is one of the western-most islands in the Canaries. 80,000 people live here making their living from farming and tourism. There are also two volcanoes on the island, one extinct, one active. In the early 1990s a British geologist travelled to the island to study the active volcano called the Cumbre Vieja.
I have a question, which came to me this week as I was in the public viewing gallery when Dr James Hanson testified on carbon emissions to the UK select committee on climate change, to which I still haven’t received a satisfactory answer.
My question is, whether building a dam across the Strait of Gilbraltar, which is only 14.2km across prevent rising sea levels in the Mediterranean and would it also help global warming by stopping the hotter Mediterranean sea from warming global sea levels?
I know that thousands of years ago the Mediterranean was naturally dammed by an ice wall (and the sea evaporated). Building a man-made dam would be technically feasible and excessive evaporation could be avoided by simply opening the dam now and then. It would certainly help the countries that have a Mediterranean coastline avoid rising sea levels. I was wondering whether cutting the hotter Medterranean off from the rest of the world’s oceans would also have a cooling effect on the world’s oceans through oceanic currents? No doubt there are other massive environmental implications of such a project that could render it unworkable. Just a thought.
>My question is, whether building a dam across the Strait of Gilbraltar, which is only 14.2km across
pretty long and on a small quake zone, but maybe.
>prevent rising sea levels in the Mediterranean and would it also help global warming by stopping the hotter Mediterranean sea from warming global sea levels?
plus the additional effect of hotter Mediterranean evaporating more rapidly, giving rise to water vapor -> eventually clouds… increasing turbidity in the area… I can’t work this out.
>I know that thousands of years ago the Mediterranean was naturally dammed by an ice wall (and the sea evaporated).
You’re probably talking of ‘Messinian salinity crisis’ (but my source is Wikipedia :-) ), I’ve understood that was caused by a series of earthquakes blocking the Gibraltar.
>Building a man-made dam would be technically feasible and excessive evaporation could be avoided by simply opening the dam now and then.
No need for this as there is Suez Canal, I don’t know if it is wide enough for the flow.
>It would certainly help the countries that have a Mediterranean coastline avoid rising sea levels.
Agreed. No reason to believe someone would terrorize it.
>I was wondering whether cutting the hotter Medterranean off from the rest of the world’s oceans would also have a cooling effect on the world’s oceans through oceanic currents? No doubt there are other massive environmental implications of such a project that could render it unworkable.
See at least “Lessepsian migration”, “eutrophication” can happen on a large scale as in the Baltic Sea.