Why do both lines (red: data, and blue: predictions) both change between figures 1 and 2? If the same corrections is being applied to both series for the land storage effect then why would the agreement between the curves improve?
[Response: Our approach is called semi-empirical because the basic formula is physically motived (e.g. melt rate proportional to warming) but the parameters (proportionality constant) are determined empirically by fitting to observational data. As two different sea level data curves were used, the model fit is also different. Note that the basic shape of the model curve is pretty well determined by the shape of the temperature curve. -stefan]
I find it sadly ironic that the big picture is often ignored to focus on a distraction.
Example: If global warming causes a land based glacier to melt faster, which thereby adds more water to a lake, the lake level rise would then be used as a claim that global warming is not happening because there are supposed to be more droughts and in a warmer world the water would evaporate faster and the lake level would go down. Obtuse reasoning seems to remain the game.
I may be misinterpreting what was done in the rebuttal, but:
Is it fair to say that the semi-empirical model “predicts” the acceleration minimum, if it is calibrated to the full SLR record, which has an acceleration minimum in it? It’s not really an independent prediction.
It’s reasonable to expect an acceleration minimum in SLR based on the time series behavior of the temperature record alone, but that expectation presumes a certain relationship between temperature and SLR. It’s dangerous to “peek” at the historic SLR data to hone that relationship, if you’re interested in historic SLR hindcasts.
A possible alternative: for each start year Y, fit the semi-empirical model to temperatures and SLR before Y. Use that fit to predict the SLR acceleration (to present day) based on temperatures – but not SLR – since Y.
[Response: As I responded to #1, the basic shape of the predicted curve is set by the shape of the temperature curve; by fitting the parameters we can do things like tweak the amplitude and add a constant linear trend to the sea level (which would not affect the acceleration). But still it is a good idea to do out-of-sample validation, e.g. fit the parameters for one half of the sea level data and then predict the other half. That is what I did here (albeit for the original Rahmstorf 2007 model, not the Vermeer&Rahmstorf 2009 version). -stefan]
Just a general comment: Measuring sea levels, sea level rises, and rise accelerations has always struck me as tantamount to measuring the breadth of say the Atlantic Ocean with a micrometer. No matter how much care and sophistication is taken in the measuring process it seems grossly flaky. But its somewhat similarity with climate models makes it a tad interesting and not deserving to be discarded out of hand. Still I don’t think it tells us much. The global average sea level was accelerating at 0.016 mm/year^2 in 1900? Really??
My criticism applies equally to Houston & Dean and Church & White 2006, though I too would add their 1930 cherry picking as an added criticism.
Sea level rise seems to be most concentrated in the southern hemisphere. Why? I am assuming thyat, though the volume of seawater is increasing due to post glacial era melting, so causing a rise in sea level around the globe, in the northern hemisphere,where ice sheets were extensive over Eurasia and N America, isostatic uplift is currently ofsetting yhe eustatic rise in sea level. Northern Britain, for example, is still rising in compensation for the loss of the ice sheets, as is Scandinavia. Southern Britain and Europe are apparently sinking, presumably due to lower rates of isostatic uplift and a contemporaneous rise in sea volume. Presumably, the Southern Hemisphere, being composed of mucch larger extents of ocean than land mass, were not affected in the same way by ice sheets, so isostatic uplift has been low or non existent. The rise in water volume in the oceans will therefore register as a rise in sea level. Am I correct in this? Can someone explain any other mechanism that results in sea levels rising more in the Southern Hemisphere?
[Response: This is not the reason. The most likely reason to me is simply natural variability. The ocean water can move between different ocean basins or between northern and southern hemisphere on long time scales due to poorly understood variability modes. These motions do not (at least not directly) affect the global mean sea level - it's just water moving about, no volume added. But superimposed on the global sea level rise, they can make the time history (and hence the acceleration) look different in different places. Of course it is also possible that there is some reason related to anthropogenic warming that makes sea level rise evolve a bit differently in the northern and southern hemispheres - could be any of those reasons that cause regional variations in sea level, such as changes in winds or ocean currents, the ice gravity effect etc., discussed more in our recent Kemp et al. PNAS paper. This difference between NH and SH is not a question I have looked into yet. -stefan]
Just a general comment: Measuring sea levels, sea level rises, and rise accelerations has always struck me as tantamount to measuring the breadth of say the Atlantic Ocean with a micrometer. No matter how much care and sophistication is taken in the measuring process it seems grossly flaky.
To Comment 9: There is an immediate gravitational feedback when ice mass is lost. The Greenland ice sheet attracts water, so when it loses mass, it attracts less water. There should also be an elastic rebound associated with present-day ice loss. You were describing the viscous rebound response, which is important but related to past deglaciation, not so much present-day melting.
see Nature Vol 462| 17 December 2009| doi:10.1038/nature08686
Probabilistic assessment of sea levelduring the last interglacial stage
Robert E. Kopp, Frederik J. Simons, Jerry X. Mitrovica, Adam C. Maloof & Michael Oppenheimer
In the first half of the 20th century:
1 Air pollution was increasing
2 artificial lakes were filling up, as behind Hoover Dam.
I don’t understand why you call it a Mid-century plateau. 1930 is before mid century.
[Response: The mid-century plateau is in the global temperature. This affects the acceleration found for the period 1930-2006, which is the point plotted at year 1930 in the acceleration graph shown. -stefan]
Measuring sea levels, sea level rises, and rise accelerations has always struck me as tantamount to measuring the breadth of say the Atlantic Ocean with a micrometer.
Yeah, and you know what else is happening to these goofy scientists and their goofy sea level measurements? The moon is moving farther away from the Earth every day! Talk about throwing a wrench into the gears. And how do they think that they know that? They ‘measured’ it. Crazy.
I know Drs. Houston and Dean personally, Dr. Houstion was my first boss at the USACE ERDC CERC (now CHL). I have had some further interactions with Dr. Houston up through 2008 (working for Drs. Resio and Fowler on a military project called LMCS (Lightweight Modular Causeway System), think D-Day landing type infrastructures).
I worked with Dr. Dean on an experimental study for the Port of Long Beach back in the mid 90′s.
The seeds of their paper in JCR can be seem in the 87th CERB meeting;
One of the CERB board members, Mr. Headland, who I also know personally (when he worked for the Navy and where he now works at Moffett & Nichol), using a FEA/FD numerical model of 1st/2nd order moored ship motion (think harbor resonance and floating bodies (e. g. large ships)) for the Ports of Los angeles and Long Beach, also in the mid-90′s timeframe.
With regards to the CERB meeting read the Dean and Houston presentations as well as the discussion sessions including the comments from Mr. Headland.
Most of the CERB discussions border on the mostly uninformed with respect to current state-of-the-art climate science. I actually got quite a few chuckles reading those discussions. Note that AFAIK, no modern day climate scientists (Dr. Seymour excepted) attended this CERB meeting (I’ll gladly stand corrected if others here spot other climate science subject matter experts (or SME’s)) who attended this CERB meeting.
But wait, there is even more background on Drs. Houstion and Dean relating to the American Shore and Beach Preservation Association (Dr. Houston vs Dr. Orrin Pilkey) and the Florida Shore and Beach Preservation Association (Dr. Dean). Those materials date back to the 80′s/90′s timeframe (Dr. Dean has two recent articles published in the FSBPA). I will expand on this somewhat in a future post.
The main question has always been, should we here in the USA build on the beach and should we protect or renourish said same beaches in the face of said building of the beachfront. Policy and politics rule the day here, at the local, state, and national levels (think Federal Flood Insurance Program in the coastal zone).
I started working for the USACE in 1983 at the FRF in North Carolina, even then, I wondered if it were prudent to build on and/or restore the beach through renourishment and/or protective structures.
If anyone here is from NC, I suggest you travel from Duck, NC to Currituck, NC, in my personal WABAC, circa 1983 (FRF) and circa 2006 (military symposium of Dr. Resio’s). What was once undeveloped beachfront, is now wall-to-wall million doller beachfront properties.
My position then, as it remains to this day, is that we should NOT be building on the beach (mainly the Barrier Islands of the USA) and/or renourishing those said same beaches.
My bias lies in that I’m not a Sand Engineer and that I abhor sand engineering, in general, but particularly on our very low profile (think elevations/coutour maps) Barrier Islands. Let’s just say that I like to engage in civil/structural engineering of a much less ephemeral nature.
The counter argument, presented mostly by Dr. Houston, was for tourist trade and economical reasons, and it is that we should try to maintain those said same beaches, either at the local, state, and national levels.
Fast forward to 2011 and we now know a whole lot more about climate change and potential future sea level change.
All indications, from the Arctic and worldwide surface temperatures, melting and movements of the Greenland/Antarctica ice sheets perimeters, Arctic and worldwide sea surface temperatures, Arctic sea ice extents/areas/volumes, atmospheric CO2 concentrations and the oceans (limited and apparently reduced) capacity to uptake these increased CO2 concentrations in a warming climate, particulates (soot depositions in the Arctic and perhaps even spring releases of particulates from the Arctic flora)) (think about all those black/dark materials at the bottom of Greenland melt ponds (actually all over the place but mostly seen and accumulated where annual melting occurs), where the fact that fresh water has a maximum density at 39.4 degrees F (e. g. the densest waters of melt ponds will lie at the bottom of said same melt ponds (~4C above it’s freezing point), which have always existed, and which maintain pathways to the bedrock over the millenia, throughout the waxing and waning of our current ice age).
I have a whole lot more to say on this paper, the JCR position on sea level change (as reflected in other published papers in JCR), a brief history on getting published in JCR (emails from Dr. Houstion (dating from the 80′s/90′s which I no longer have BTW)), and even some criticisms of the works Stefan and Martin and others on extrapolation of future sea level changes (but basically, one needs to be very careful of these extrapolations when the steepest part of the curve occurs at the end (present day) of said calibration/verification efforts, when the present day empirical data appear to suggest that we are not NOW at the steepest point of said sea level change).
I will keep this current post relatively short by ending here. But expect future posts on said subject matter in the very near future.
PS – Thanks Stefan for the Reply to JCR, I was thinking basically the same thing (a reply to JCR), but I’m not an expert on sea level change as you and many others are (the works of Church immediately come to mind, but there are many others). I will now read your JCR reply, but your abstract pretty much sums up the technical opinions that I had/have at the time of publication of the Houston and Dean paper).
PSS – Well actually kind of a long opening post on my part.
PSSS – I will gladly accept any counter arguments (here or elsewhere) directly from Drs. Houston and Dean, or any of their minions, or anyone else for that matter.
Your numbers do not look right. I’m no ocean scientist, however my general understanding has been that ocean levels have been steadily rising by between 0-4 mm/year. Currently have been slowing down a bit to 2 mm/yr.
> American Shore and Beach Preservation Association …
> and the Florida Shore and Beach Preservation Association ….
> build on and/or restore the beach through
> renourishment and/or protective structures.
That’s a good reminder — this is a crucial assumption for a large scale industry dedicated to propping up the value of real estate along the ocean by using state and federal dredging and construction.
Don’t expect it to be a science question; investment has long since taken place and the time for ecologically rational decisions passed long ago.
Yes, I spent most of my childhood summers on the Outer Banks and recall what they used to be like. They were beautiful.
I’d think it reasonable to expect socks and mock-grassroots activity.
Interesting chart in response to comment 20. Regardless of any acceleration in sea level rise over the 20th century, it sure HASN’T accelerated since 1994 according to the data – an overall fairly linear appearance.
And since around 2006 (and even starting on the linear trend point), the appearance from the plot is that the rate of increase has slowed down.
It’s apparent then that since 2006, the answer to the question is ‘No’.
The next few years I think will be interesting given what I have seen about the lull in solar activity, from a sunspot and solar flux standpoint . . .
This is agreed something between 0-4mm/yr and that’s not the question. Recently the rate has been going down and is currently around 2 mm/yr. And your data only starts in 1993. Look at the trend going back further. There’s little change from 0-4 mm/yr.
I dont really understand why the CI’s are so large post-1960. Are these limits reflecting uncertainty in the measurement or uncertainty in the fit of the equation? (sorry if this is a dumb question)
[Response: It is simple: the shorter the data series, the more uncertain the estimate of a trend or (in this case) a quadratic term becomes. Remember the curve shows acceleration from year X up to 2006. So for 1960, that is acceleration over the interval 1960-2006 which is starting to become a rather short period. Hence the results start to become quite sensitive to small changes in the start year, i.e. rather noisy and less robust. -stefan]
Ian and JimA
As you can see from the chart, in the response to comment #20, that a similar decrease in rate of sea level rise happened in the early to mid 90s and again after 1998. And you can see how meaningless they look relative to the overall trend.
And if you really look, you’ll see that cherry picking like this is ubiquitous at skeptic websites and with their claims.
What do you mean by acceleration being “twice the quadratic coefficient” (in your caption to figure 1)? According to my understanding of calculus, acceleration is the second differential of position with respect to time, i.e. d^2x/dt^2. Fitting a curve to a quadratic equation, i.e. to an equation of the form y=Ax^2+Bx+C does *not* equate to a determination of acceleration, but is merely curve-fitting.
An explanation would be appreciated. Thanks.
[Response: The independent variable is time and the dependent one sea level (not position), so we are fitting (just following Houston and Dean btw. for the purpose of the rebuttal - we favor relating sea level to temperature, not time): x=At^2+Bt+C. Now take your second derivative and the result is 2A. That is why we say the sea level acceleration is twice the quadratic coefficient (again just following Houston and Dean here). -stefan]
I agree with the comment that it seems madness to continue to build along beaches and low lying land. As a structural engineer in Australia, there seems to be a huge blind spot with this one. I think it is partly driven by those who own the land thinking that they will be able to sell it when they want and convincing themselves that the impacts are a long way into the future.
Some are simply taking the attitude that they will enjoy it while the sun shines!
Unfortunately, people are going to get caught and won’t be insured whent he storm comes in and they lose everything.
By the way, our brave Prime Minister is trying to establish a price on carbon – it looks lke it will pass the parliament. What happens if we get a change of government is still in question as the opposition leader is saying he will wind back the legislation.
Thanks for the response Stefan. I agree that the second derivative of the equation x=At^2+Bt+C simply gives 2A. Using this in the context of sea level, however, assumes that the shape of the plot of sea level as a function of time follows a quadratic relationship. I see no physical basis for this.
[Response: We say this in our comment.]
The actual data, as you have reported it, does not in any case follow such a relationship. Doesn’t it make more sense to derive a derivative from the data itself?
[Response: You'd get a wildly fluctuating curve (you do even for the first derivative). If you want one number for the acceleration over the entire period 1930-2006, or 1950-2000 or whatever, then you'd fit a quadratic to that period to reduce to one number what would otherwise be a curve. -stefan]
Regarding your response to Comment 20, the graph you show does not show sea level rise accelerating, rather gently decelerating.
And don’t forget that this data isn’t even the real sea level as it has had an isostatic adjustment (GIA)applied to it. If you want the actual sea level you have to subtract 0.3mm/yr … which leaves an even flatter curve. Average rise over the period (1994-2011) is only 2.8mm/yr and over the last 10 years or so is definitively less than 2.
Why are you so insistent on the idea that sealevel rise is accelerating, when it obviously isn’t.
[Response: Umm... because it is? Quick question for you, what was the SLR over 1900-1950? What is it over 1960-2010? Which number is bigger? You seem to be thinking that these statements are about short -term (decadal) trends when everyone else is discussing much longer trends where there is less noise. - gavin]
[Response: Read our comment in JCR - decadal trends are dominated by sampling noise. They don't agree between different data sets. -stefan]
They begin by using OLS on a quite arguably non-stationary process, very bad move on their part. See discussions on random walk, unit root, and more advanced statistical methods that should be applied in non-stationary time series analyses.
However, note that statistics alone does not include the underlying physical processes themselves, there is no physical basis (e. g. physics based) for their quadratic curve fitting methodology. The statistics alone cannot explain causality, as in correlation does not equal causation, basic first principles type stuff.
Their “model” is a simple double integration of time, and they even carry the 1/2 term as follows, y =A*t^2/2 + B*t + C, which is very old school, as this is just a 2nd order polynomial (please drop the 1/2 factor).
There solution space is thus totally bounded by the constant curvature of their quadratic term, all explanatory power of their model is left in the constant “acceleration” term (A/2 in their nomenclature). Thus, this is but one, of many possible curve fitting approaches, that will have virtually no skill if extrapolated into the future, something that all real phyical based models should strive to achieve.
Next up? Their capricious and arbitrary definition of record length, why 80 years? Why not 100 or 60 or even 40 years. Did they perform any kind of statistical metrics to arrive at this arbitrary number? In a word, no.
Thus, the very valid claim of cherry picking arises as Stefan has noted above.
Finally, looking at the global temperature curve, with it’s rather large bump in the 30′s/40′s, and with the full expectation that sea level rise would lag this temperature curve significantly, strongly suggests that the resulting sea level curve would be an offset upward bulge right in the middle of said sea level curve (in other words, a monotonic temperature curve would have producd a concave up sea level curve), and largely mask the actual underlying “acceleration” when curve fitting against time as the only independent variable.
Note: I really hate using the term “acceleration”, as this has only one meaning in a strict physics based sense, a power law, or an exponential fit, does not exhibit a constant accelleration, any exponent greater than one is by definition non-linear and concave up.
I’ll leave you with with a direct and strangely ironic quote from the H&D reply;
“However, they are curve fitting, not modeling physics, so the approach cannot be used to predict future sea level.”
So yes, H&D are surely curve fitting, and not a single physics based equation is to be seen in the entirety of their paper. Go figure.
Martin C, you don’t seem to have grasped the significance of the article at the top of the page. Firstly, the acceleration is small. It is very hard to see with the naked eye. Secondly, the data is noisy enough that it is absolutely impossible to come up with a meaningful eyeball estimate of the acceleration from a mere 15 year snippet of data.
Look at the very first graph: you need over 40 years of data to get reasonable error bars. The satellite data is higher quality, and does allow calculations of acceleration with far less data, but still you can’t do it without actually running the numbers.
Nearly all curves “look linear” if you focus on a small enough segment. This is how computer graphics work: curves are approximated with short lines.
The comments about beachfront property are really interesting to me, as I used to be a reporter in Florida.
I remember speaking to the guy whose job it was to do disaster planning for Charlotte County. (This is located south of Tampa and north of Fort Myers, on the Gulf Coast). I looked at a flood map in case of hurricane storm swells, and was, frankly, appalled. Half the county was underwater with a relatively weak (category 3-ish) storm.
I asked him then, why in the name of all that lives do people build anywhere near the beach? Or at least, why build with the design (basically a house on a slab of concrete) that virtually guarantees the house will be utterly destroyed? It isn’t like hurricanes in Floria are a surprise, one shows up at least every other year or so.
Now, I come at this as a native of New England. We get storms there too. And when people build near a beach, we don’t mess around. If you go to Scituate or Hull you will see houses on pilings. Big pilings. Pilings (and houses) that have stood for a century and are deep into the sand and soil. Where I am from you can see, under the WWII – era seawall, examples of the original works that were built. Many coastal homes are also built on the rock, anchored there. (Granted, the rocky-ness of the coast on the North Shore lends itself to this).
But nobody in their right mind would ever, ever build a Florida-style house on Nahant or the Cape. And I think it says something that so many homes in my home area have stood for 100 or more years, facing some of the biggest storms that the North Atlantic and Hurricane Belt could throw at them.
I got a very interesting answer from the disaster recovery official. He mentioned two factors: one is that people who move to Florida are often from areas that are not near the sea. “You respect it, you grew up with it” he said. “They don’t.” (This was, as an aside, also the reason he said the state led the US in accidental boating deaths).
The other issue is property values. Everyone wanted a beachfront house. But to build them up to snuff would take a lot more money than the developers were willing to spend. New England is proof that you can build one heck of a sturdy house near a beach. But that is going to cost you. Your profit margin, as a developer, from flipping the house is going to be much reduced. And in Florida, if there is one lobby that is powerful, it is real estate. Now, the developers who flip the houses have no incentive to build anything that will stand longer than a few months, as they are out of the game once the home is sold.
I might add that Charlotte County recently experienced a hurricane (2004) and 5 people were killed in the county.
The science is pretty clear: sea levels are rising. Coastal Florida counties have a choice. They can do what the Dutch did and do, but the costs will be high and it will mean vast changes in the way Americans live in Florida. Or you can stop building in sight of the sea. (And don’t allow people to re-build there). The cost there is much less and fewer people die, though the real estate lobby loses out.
In one of your recent threads you discussed a paper on salt marsh sediments that showed a global 2.1mm per year rise in sea level for the last century. Your acceleration figures appear to be about 50x smaller than this. Can we conclude that variations in sea level in the technological age are dominated by non CO2 related phenomena? Or would it be equally reasonable to suggest that quoting sea level rise acceleration accurate to 1/100th of a millimeter, given that the Church White data is based on tide gauges.
Is short term sea level rise prediction factoring in relative fluctuation in actual Atmospheric Pressure, I was talking to Proffesor Le Querre some time ago, and their’s a few more questions to be raised ?
[Response: This is called the "Inverse Barometer" affect and can be corrected for (http://sealevel.colorado.edu has graphs with and without this correction). Basically, if you have a atmospheric low pressure system compared to a high pressure system, sea level is just a little higher (for a 10mb difference in atmos. pressure, you get a 10cm rise in local sea level). It doesn't make much difference to the long term global trends but it does reduce the variance a little. - gavin]
I took the satellite data from the University of Colorado sea level site and spit it into two equal halves. I charted the data and ran trend lines through it. The rate in sea level rise for the first half was 3.4 mm/year. The rate of rise of the second half was 2.1 mm/year. For the satellite era at least, the rate of sea level rise is falling. The rate that is shown by the second half of the satellite record would give us 8.3 inches of sea level rise in 100 years.
[Response: Is it conceivable that linear extrapolation is not the optimum way to assess risk? - gavin]
I’ll have to keep this brief so as not to go to far off topic.
Here in the USA we have FEMA which with the help of the USGS, USACE, NWS, and private concerns defines the 100-year flood plains everywhere (inland and coastal).
We also have the Federal Flood Insurence Program, which is the only way to get flood insurence if you live ABOVE the 100-year floodplain.
Above is a very important word when one builds in the coastal zone (but above still applies in all situations).
So what’s a person to do? Well most states have building coded that require you to build your beachfront property above the 100-year FEMA floodplain.
To do so, requires you to build your home on stilts and most (if not all) state codes also require that the void space between the ground elevation and the actual 1st story be kept clear of any obstructions.
So what happens if your multi-million doller beachfront home is destroyed during a hurricane and you also have flood insurance? You and I get to pay for it’s replacement (seriously, through our tax dollers).
From the FEMA website;
“When property owners receive financial assistance from the Federal Government following a Presidentially declared disaster, they may be required to purchase flood insurance coverage.”
When has the POTUS not declaired a disaster when a whole bunch of people get flooded out? AFAIK never.
Finally, older existing ground level homes are grandfathered, in that they can’t get flood insurance, but these structures are still habitable and, of course, sellable.
I hove some more to say on this subject matter, with respect to sea level rise, and changing state policies that would require building your beachfront property on higher stilts (e. g. NC is recommending an additional one meter increase);
[Response: Is it conceivable that linear extrapolation is not the optimum way to assess risk? - gavin]
Yes, it is very conceivable. However, basing risk on assumed acceleration of sea level rise when there is actually deceleration would seem to be even less predictive than linear extrapolation. And while there may have been acceleration going from the pre-satellite era into the satellite era, that acceleration has now ceased and changed to deceleration.
[Response: Is it conceivable that any kind of statistical extrapolation is not the optimal way to assess risk? - gavin]
# 47 Tilo Reber? No plz, my head is about to explode… a proven cherry picker. Got a link to a ‘Reber’ person with the title ”Why Reber is Wrong”, think it was penned by BPL similar to a “Why Tim Ball Is Wrong” which works, but the link Reber went dead. Help nearby, there is the inimitable Google and low… http://bartonpaullevenson.com/Reber.html
As a geologist, I take a longer-term perspective. The current rise in sea level began some time between the mid-19th to late 19th century–after the end of the “Little Ice Age”, when the Earth started to warm up again and mountain glaciers worldwide began to recede, but the average global SL trend over most of the 20th century has been ~1.7-1.8 mm/yr based on various compilations. Since the advent of satellite altimeters in 1993, the trend has been ~3 mm/yr (combined satellite and tide gauge data). Does this represent an acceleration? Possibly. The longer this trend persists, the more likely so.
By the way, the latest paper by Church and White (2011; Surv. Geophys. publ. online Mar. 30, 2011) reports a linear SLR of 1.7 mm/yr 1900-2009; 1.9 mm/yr 1961-2009; satellites 3.2 mm/yr 1993-2009; tide gauges 2.8 mm/yr 1993-2009. They conclude that there has been a statistically significant acceleration since 1880-1900 of 0.009 +/- 0.0035 mm/yr2.
What makes recent sea level rise noteworthy is not so much the interdecadal fluctuations–like the apparent deceleration of the 1930s, noted by several authors, likely associated with a Northern Hemisphere temperature decrease around that period (cause??), but rather the overall increase in the 20th century trend (by 1-2 mm/yr in many cases) relative to that of the preceding millennia (can cite reference upon request).
While this seeming “bombshell” seems newsworthy, mainly because the climate skeptics are jumping on it, should it merit more attention, than say some of the other recent climate controversies, like the flap about the leaked e-mails and questions over Michael Mann’s “hockey stick” curve, because of a few dubious tree ring records, or a poorly documented claim about how soon Himalayan glaciers will disappear?
Comment by Vivien Gornitz — 13 Jul 2011 @ 11:05 AM
The way things are going now, it would seem that sea level rise will have to accelerate quite a bit, if it is going to catch up with drought as a serious problem.
Comment by SecularAnimist — 13 Jul 2011 @ 12:01 PM
Sekerob: “Help nearby, there is the inimitable Google and low…”
Yes, unfortunately Barton was wrong. I used monthly data that came up to date, Barton used yearly data that didn’t. For some inexplicable reason Barton seemed to think that trending yearly data was more accurate than trending monthly data.
Barton claimed that my flat trend was based on ENSO cherry picked end points; I showed Barton that you could use ENSO corrected data and still get the same flat trend. Of course there was no chance that Barton was going to let me give my side on his web page.
I’m assuming that since Gavin let you attack me on a subject that had nothing to do with the thread, that he will let me defend against that attack.
Response: This is called the “Inverse Barometer” affect and can be corrected for (http://sealevel.columbia.edu has graphs with and without this correction). Basically, if you have a atmospheric low pressure system compared to a high pressure system, sea level is just a little higher (for a 10mb difference in atmos. pressure, you get a 10cm rise in local sea level). It doesn’t make much difference to the long term global trends but it does reduce the variance a little. – gavin
You do need to know that when you’re trying get the Nimitz into a port with a Sand Bar ?!
From what I can tell and from my personal conversation Professor Corrine the biggest problem with accurate readings is the actual effects of the escalators : I saw a schematic about 10 years ago and they’re swinging widely, but they’re not shutting down, the tips seem to feed of ice, oscillating, feeding the convection current, preferring cold to warm rather vice versa ? : i strongly suspect theirs a few other issues involved.
the key driving mechanisms of the chaos of the planet’s weather systems, and that’s the question of whose budget ?
and it’s not being factored into the equation : and that’s an ask nicely we might be able to get a military satellite re-directed.
If more than 40 years of data is required to get a better ‘trend’ , then see the following link – it contains a chart showing global cumulative sea level change for 1900 to 2002
[http://www.wamis.org/agm/meetings/rsama08/S304-Shum_Global_Sea_Level_Rise.pdf]. The slide I am referring to is the 14th slide in the presentation. And this presentation is concerned about sea level rise from C02 warming . . .
Not much of an acceleration on the plot, and you mention with this article, the acceleration is small and hard to see.
Yet even IF sea level rise were accelerating by 0.2 mm/yr), starting with a 3.2 mm/yr increase (per the University of Co. website), the increase in sea level over 20 years would only be about 4 1/4 inches. Easy to adapt to. But let’s watch the data over the next 5-10 years to see how the trend is changing first.
[Response: Am afraid you're still not getting the time scale involved. In our Vermeer and Rahmstorf 2009 paper we use ~15-year averaging for the data. The entire satellite record is one data point (which very nicely fits our model, although this point is not used in calibration). To get the next data point which might give some reasonably independent info we now have to wait another 15 years. Anything shorter is noise - judging from the past data - and not in any way correlated with the temperature evolution. -stefan]
So, not only is the rate of sea-level rise accelerating (a horizontal blue or red line would show that), but the rate of acceleration is itself increasing, and until recently not just linearly (a line of constant slope would show that), so the rate of acceleration has itself been accelerating. Phenomenal.
The latest Church & White update includes a plot of a simple average of tide gauges, plotted in hard-to-see yellow on top of darker plots that obscure it’s linear nature, one that shows no trend change going back 150 years: http://i.min.us/idFxzI.jpg
What is labeled “mean sea level” in their final up-swinging graph is not really actual sea level but one “corrected” for the estimated effect land based water reservoirs, this correction is not referenced except as a “private communication.”
#63 Paul S referenced Chao’s claim that reservoirs have subtracted 3 cm from the sea level. I point out that this means that minus AGW-caused enhanced sea level rise, a seemingly unexplained natural dive in sea level of 3 cm has been nearly exactly avoided, due to the trend in tide gauges being so linear (larger image of the Church & White 2011 plot here: http://oi51.tinypic.com/28tkoix.jpg). That seems a bit odd, given that T has been rising in that same 150 years. Minus a mechanism for this avoided dip, the argument that actual sea level should be replaced by a virtual one is much less convincing.
Are HD the zen masters of the cherry pick? Absolutely!
From there 2nd paragraph in their reply to RV, HR state;
“In Figure 1, RV show only the data that agree with their
model. On the x axis of Figure 1, record lengths are shorter
than 60 years for starting years after around 1940. It happens
that at around 1940 the acceleration shown is approximately
zero. Thus, as seen in Figure 2, the record from 1940 to 2001
has a strong linear trend with decadal fluctuations but
approximately no acceleration. If the record from 1940 to
2001 has zero acceleration, how is it then possible that all
shorter records (starting years after 1940) shown in Figure 1
have positive accelerations that increase as record lengths
shorten? It is not possible. Again, RV only plot the data as long
as they agree with their model. If the plot is extended, e.g., to
the starting year of 1985, the acceleration is 20.044 mm/y2,
more than twice the range shown for negative accelerations in
Figure 1. If the plot is extended further, the folly of analyzing
records shorter than approximately 60 years becomes increasingly
obvious. The acceleration for a starting year of 1995 is
20.51 mm/y2, about 25 times the range shown for negative
accelerations in Figure 1. RV compare their model to data as
long as there are positive accelerations and do not continue the
plot when accelerations become negative, which must happen
for the overall record from1940 to 2001 to have an acceleration
of approximately zero.”
So who exactly, a priori, are assuming acceleration as the only possible answer, in the strict physics based sense anyways? HR are.
“It is not possible.”
Exactly, but only if you a priori choose a constant curvature (in time as the independent variable as opposed to temperature as the independent variable) quadratic term, which does not have a shread of physical basis whatsoever.
HR then go on to suggest that RV only present data results (Figures 1 & 2) that support their modelling assumptions.
But that is not the case, as HR so blatantly prove themselves, by choosing start years of 1985 (17 years of observational data) and even 1995 (now down to just 7 years of observational data).
As RV rightly point out, these start dates are just too short, statistically speaking, to inform anyone about anything.
“the folly of analyzing records shorter than approximately 60 years”
“Houston and Dean (2011) considered only tide-gauge records with lengths greater than 60 years, noting that shorter record lengths are ‘‘corrupted’’ by decadal fluctuations.”
So apparently, “tide-gage records” longer than 60 years are not ‘‘corrupted’’ by decadal fluctuations.
Didn’t know that.
So, according th HR, I cannot go O(120) or O(100) or O(60) or O(40), I can only go O(71) or O(80), or somesuch.
I must use “tide-gage records” only and I must concentrate them CONUS, apparently.
Are HR engaged in begging the question? You betcha!
See my first post on the 87th CERB meeting, whence it was required that this be published in some form somewhere within the entire body of the peer reviewed literature, the outcome being this JCR publication.
You see, the USACE needs better guidance on SLR than they have had to date.
They’ll cherry pick which IPCC guidance the like and throw out IPCC guidance they don’t like.
They’ll crerry pick an a priori quadratic curvature they like and throw out all other models they do not like.
They’ll cherry pick the start year, the tide gages and their locations that they like and throw out all other data sources and timeframes they do not like.
Whom better to “advise” the USACE on new and improved SLR guidance than the former (Director Emeritus) of the USACE ERDC and a former (Professor Emeritus) long standing CERB member themselves?
Conflict of interest you say? You betcha!
The USACE does not define, in and of itself, it’s own Mission Statements, those are accomplished only through Acts of Congress and the Executive branches.
This has become a rather long post (but I’m not entirely done yet, there will be future posts if the moderators here would be so kind as to let them through), so I’ll end it right aboot here.
#60 Simon Abingdon, yes it is rather subtle, but if I can understand it anyone can. The years along the bottom are start dates – think carefully what that means about the points on the line. (I think I have this right – please someone correct me if not!)
Comment by One Anonymous Bloke — 13 Jul 2011 @ 9:43 PM
Simon:”tph The x-axis does look rather like time and the blue line being shown as a smooth curve, your point must be one of some subtlety.”
Yes, it LOOKS like time, it is NOT time (my original comment). Instead it is how many years worth of data (present – minus that date) to compute a single acceleration that spans the whole time period. That is why the error bars are larger for more recent “years” even though the measurements in recent years is more precise and more accurate (also two different things subtly different).
“the warmest year in the extended Greenland temperature
record is 1941, while the 1930s and 1940s are the
Extending Greenland temperature records into the late eighteenth century
B. M. Vinther,1 K. K. Andersen,1 P. D. Jones,2 K. R. Briffa,2 and J. Cappelen3
Received 24 October 2005; revised 11 January 2006; accepted 28 February 2006; published 6 June 2006. http://www.cru.uea.ac.uk/cru/data/greenland/vintheretal2006.pdf
The Antarctic (excluding the peninsula) didn’t realy warm since 1955 according to Giss and hadcrut.
#64, NikFromNYC – The build-up of reservoirs has been gradual, as you can see on Church & White (2011) Figure 7, so both the ‘uncorrected’ and ‘corrected’ versions look pretty linear at a glance. Their detection of acceleration used the ‘uncorrected’ reconstruction, in case that is your concern.
‘That seems a bit odd, given that T has been rising in that same 150 years. Minus a mechanism for this avoided dip, the argument that actual sea level should be replaced by a virtual one is much less convincing.’
According to the HadCRUT record the trend from 1850 up to about 1930 is flat. Real temperature increase occurred after this point. Could that be a reasonable mechanism for avoiding a dip?
In order to build coherant long-term global records of sea level change some adjustments are necessary. The most well known is the correction for glacial isostatic adjustment – this is performed to ensure we are actually measuring the height/volume of the sea and not changes in height of the land.
The Chao 2008 adjustment is different because it quantifies something that actually has affected the height/volume of the oceans. Whether a study uses the adjustment should depend on the focus. Church & White 2011 didn’t use it to draw their main conclusions because they were concerned simply with how sea level has changed. Conversely Vermeer & Rahmstorf (2009) is concerned specifically with how climate changes affect sea level, so it is imperative that non-climatic influences be taken into account.
tph Thanks for the explanation. I have a question which may help me to understand, or not. If the x-axis were labelled in the reverse direction with more recent years (1970, fewer years’ accumulated data) on the left and earlier years (1870, more years’ accumulated data) on the right, the blue line would seem to be trending to about 0.02 mm/yr2, the presumably best result that 140 years of accumulated data can give us. (Sorry for wasting your time if this is hopelessly wrong.)
> CERB …
> it was required that this be published in …
> the peer reviewed literature, the outcome
> being this JCR publication.
For convenience, with applause, let me refer readers back to your earlier post. The academic publication was needed so regulations based on these assumptions could be arguably justifiable, to go on with stupid policies.
They don’t need good science, just any basis to argue for continuing to do what they’ve been doing. That’s how it works.
“… The seeds of their paper in JCR can be seem in the 87th CERB meeting; http://chl.erdc.usace.army.mil/cerb87
… read the Dean and Houston presentations as well as the discussion sessions including the comments from Mr. Headland.”
The huge new industry now dedicated to “sand engineering” and “coastal nourishment” is in the service of real estate developers — fools building on sand islands that we have known for decades are moving.
#72, alexandriu doru – Church & White (2011) incorporates an adjustment for aquifer depletion into one figure and notes that it ‘offsets perhaps a third of [reservoir storage] over the last five decades’.
Reservoir storage changes over that period have been estimated to have lowered sea level by about 3cm so that would mean 1cm of observed sea level rise over the past 50 years is attributable to aquifer depletion.
I think it’s early days though. There will probably be a few papers on it over the next year.
Simon, if the graph order of dates was reversed, then the graph would be the left-right mirror image. That said, the fit for the 100 year period 1870-1970 has the best value, about 0.016 mm/yr^2. This means that sea level rise, whatever it was around 1870, is now 1.6 mm/yr more (not a stretch given we are around 3 mm/yr now, and in order to get 1000 mm by 2100, that is an average of 10 mm/yr for the century – that means a significant acceleration is to come.
Just waiting on BPL to come around and write “Why Tilo Reber [Is Still, And Again] Wrong” if he even can be bothered to waste his time. It was a tactical apology [to shut him up in a OT, surely nowhere going polemic that could have ensued]… You know it, I know it, most know it, it makes diddely squad difference taking monthly or annual, provided there’s enough data points [years however sliced and diced] to draw meaningful conclusions from.
(Posted in parts to find the partion that causes it to be flagged as spam.)
Entertaining is the new memê of Cryosat-2 being pre-heroed by the denial-ists, who’re hoping of course that it will rubbish all prior science. Maybe PIOMAS had it wrong, but would their trend change by any significance? No hope [for them] in heck. The team will have a new reference to refine their model, for it would be foolish to drop the effort… in case Cryosat-2 fails… it’s a limited mission after all and only numb-brains will put all eggs in one basket.
Those of [willfully chosen mostly] limited capacitance will cling to 1998 as departure point [when cooling started], soon 2010, and the usual places that persist on drawing graphs from 2001 [with their cover-up act of ''randomly'' switching to 20 or 30 years data... but then only when it suites them]
No wonder what an Attack is on denialosphere scale. The super-sensitivity act when telling when their hair looks ruffled at the left ear, peddling the ”picture” of then it all being wrong :D
PS, it is still baffling to take any series that started and ended just as BPL described at the beginning of his write-up, point 2 at top, and then 3 years later the subject ”bluffing” BPL was wrong.
Sorry, too much spill of spiel in the head… wasting everyone’s time :P
re CAPTCHA: flippancy. scomens
(seems the filter did not like the alternate for horse manure)
[Response: See above. You can cling to La Niña-related dips if it makes you feel better, but the long term trend is up. - gavin]
So how long would I have to wait with the points at their current level before the CAGW hypothesis is falsified?
[Response: Well, you'd first have to tell me what the 'CAGW' hypothesis was and what predictions are supposed to follow for sea level rise. Since I do not see this hypothesis defined anywhere in the IPCC report, I am not really clear what source you are referencing. Thanks. - gavin]
“Of all the various anticipated impacts of global climate change, sea level rise will likely be the first to produce a human catastrophe on a global scale….
… the Intergovernmental Panel on Climate Change (IPCC) threw up their hands on this issue and in 2007 issued only a partial prediction. The panel said that sea level could be expected to rise 11 to 23 inches by the year 2100 but this number, they pointed out, included mainly thermal expansion and did not include the meltwater contribution from the great ice sheets. Unfortunately, many groups have mistakenly assumed the 11-to-23-inch prediction to be the total anticipated sea level rise. The IPCC is a committee of 2000 plus scientists, which perhaps explains the fuzzy wording of the sea level rise prediction that has led to widespread misinterpretation.
Panels from various states and nations have since filled in the predictive gap and come up with their own predictions….”
Here, I think, is Pilkey’s answer to Dixon’s question, the conclusion of that article:
“… For the sake of the beaches we can only hope that a real retreat policy will be instituted and as communities are abandoned, their buildings will be demolished and removed. Otherwise we can expect that within 40 to 60 years, the world’s beaches will begin to be lined with debris from abandoned and deteriorating buildings providing much hazardous material to pollute the oceans.
If our beaches are to survive for our grandchildren’s enjoyment, the time has come to plan the big withdrawal.”
So, Dixon, you’re standing on the tracks and a train is coming: do you wait to see if it’s an illusion? Insist on your right of way? Do something to avoid being hit? What if it’s your grandchildren in harm’s way?
gavin wrote: “… you’d first have to tell me what the ‘CAGW’ hypothesis was …”
I believe it is the hypothesis that at some point in the future, anthropogenic global warming (‘AGW’) will cause catastrophic (‘C’) effects.
Like, for example, catastrophically destructive effects like record-breaking droughts, heat waves, flooding, violent storms, degradation of coral reefs, etc. occurring all over the world simultaneously, incurring billions of dollars in damages and negatively affecting agricultural output.
I suppose one could say that the hypothesis that such events will occur in the future has been “falsified” since such events are already happening now.
I think Pilkey makes the point that it’s our preparation — or failure to prepare — that determines whether a catastrophe happens. That’s true more and more as the science informs our choices.
Making bad choices is the catastrophe — it’s a human choice.
“According to the book ‘Denial of Disaster: The Untold Story and Photographs of the San Francisco Earthquake and Fire of 1906,’ not only were the defects in earthquake and fire resistance repeated in the rebuilding, but “building code standards were actually reduced from those in effect before the Great Fire….
… days after the earthquake, The Chronicle reported that the Real Estate Board resolved that the phrase “the great earthquake” would hitherto be known as “the great fire.”
… seismic safety did not play as large a role in the rebuilding as one might expect. The primary focus was less ‘pre-quake’ mitigation (improving building and fire codes) than ‘post-quake’ preparedness (establishing a more robust system of water supply for firefighting).”
Hank — I know. I meant to write “Hank Roberts quoted” but wrote “Hank Roberts wrote” out of mechanical habit and didn’t catch it until I had clicked the Submit button. Sorry ’bout that.
Seriously though — it really does seem “likely” to me that agricultural failures resulting from AGW-driven megadroughts will be “the first to produce a human catastrophe on a global scale”, long before rising sea levels have a comparable impact.
And indeed, this is already happening on a continental scale in Africa, and the impact of unprecedented, intense, prolonged droughts on agriculture in Russia, China, Australia, and elsewhere is already impacting the world’s food supply.
And it seems entirely possible that acceleration and intensification of such droughts could lead to world-wide crop failures in a matter of years, rather than decades. We could be literally just a few years away from an unprecedented global famine, which makes it hard for me to get worked up about the possible impacts of sea level rise a century from now.
And ends (to date anyways, except for the aforementioned thread topic) right aboot here (The ASBPA’s Shore & Beach Vol. 76, No. 4, pp. 22-26), “The economic value of beaches – A 2008 update” by James R Houston);
THE ECONOMIC VALUE OF BEACHES A 2002 UPDATE (S&B, V70, N1, pp. 9-12) by James R Houston
COASTAL FORUM – MYTH OF THE SUBSIDIZED BEACH RESIDENT (S&B, V67 N1/2, pp. 2-3) by James R Houston
BOOK REVIEW: REVIEW OF THE BOOK THE CORPS AND THE SHORE BY O. PILKEY AND K. DIXON (S&B, V67, N1, p 27) by James R Houston and Robert Dean
REVIEW OR REBUTTAL? A RESPONSE TO “REVIEW OF THE BOOK THE CORPS AND THE SHORE BY O. PILKEY AND K. DIXON” BY JAMES R. HOUSTON AND ROBERT DEAN (S&B, V67, N1, p 32) by Orrin Pilkey and Katherine Dixon
INTERNATIONAL TOURISM AND U.S. BEACHES (S&B, V64, N2, pp. 3-4) by James R. Houston
COASTAL FORUM I. BEACH NOURISHMENT (S&B, V63, N1, pp. 21-24) by James R. Houston
Conflict of interest, you say? You decide. :(
And what does Robert Dean have to say aboot all this through the auspices of the FSBPA, you say?
Wait for it, you guessed it, a BAU policy (move along, nothing to see here, it’s all just a scare tactic), why heck, the Dutch, and even Dubai, are building into the oceans, so heck maybe we should also (by implication);
“ASBPA peer reviews every article that is published in Shore & Beach journal. We need peer reviewers with a wide range of expertise. In addition to qualifications, it is important to understand that timeliness is critical. We will let you know ahead of time when articles should be expected, but they need to be turned around in a week’s time period if at all possible. Slow peer review means the journal is delayed. If you are interested in being a peer reviewer, please fill out the form below:”
So yes, you too, can be a peer reviewer of S&B.
But dag nab it, hurry up aboot it, time’s a wastin’, we have beaches to fill (with buildings and people and things and very much mulla thank you very much, oh, and lest we forget, sand, lots and lots of sand, enough sand to last the eons, and if sand won’t work, we’ll build sand berms (think CCC), and sand fences, and geotextiles, and levees, and dykes (no, not those types of dykes, get your filthy mind out of here right aboot now), and retaining structures, and walls made of straw, no make that walls made of sticks, no make that walls made of bricks, no make that walls of concrete and steel, and even dams, dam it) and what not.
So what does S&B’s peer review consist of you say?
(Choices are numbered, answers are lettered, what’s up with that?)
Why yes, you too can strive to flip burgers at a beach near you, after all, we’re just a service economy nation now anyways, or so I’ve been told, many a time, by the MSM. Life’s a beach after all, right? :(
Well I have my own one question quiz, called The Paintonomics Quiz;
You are aboot to paint a room that has only one entrance/exit (no windows or axes or explosive devices or etcetera’s), four corners, one of those four corners has a hole in the floor, which below it contains shark infested waters (but you don’t know this for sure, as you’ve never ventured into this corner, even at the pleading of many others, for you to do so for your own safety), do you;
1) Paint your way to safety (via the entrance/exit, call this one mitigation).
2) Paint yourself into one of the three corners sans the hole (call this one BAU) and wait for the paint to dry (timescale O(100) years).
3) Paint yourself into the corner with the hole, look down, see only dark waters, and say, aw, what the heck, I can swim, and time’s a wastin’ anyways, gotta go (call this one adaptation, of the worst sort, mind you).
Hmm, which to choose, well I wasn’t born three days before The Day After Tomorrow (BTW, Al Gore’s favorite film, or so I’ve been told at WUWT (I kid, I kid)) you know, so I would choose A (in keeping with the ASPCA nomenclature, mind you).
Wow, another rather long post (but I’ll have more to say (further critiques on the HD paper, as well as current (actually expired as of July 1, 2011) USACE SLR guidance (EC 1165-2-211 for those of you who want to jump ahead).
DISCLAIMER: I do not now currently work for the USACE in any capacity, the views expressed here are my own (except for the cited documents which are the works of others), and my real name is Francis E. Sargent (most people call me Frank, but my birth name is Everett F. Sargent, Jr., thus the EFS_Junior screen name (moderators, fell free to edit out my true identity as you so see fit, but I have nothing to hide)).
EFS – just a layperson here. I think it’s ironic that many of the skeptics who tout Houston and Dean’s SLR study in blog comments also complain incessantly about people choosing to live on floodplains or areas commonly battered by hurricanes.
Also, in the 1970s I lived in my Uncle’s beach house on Emerald Isle. At that time there still was a lot of open land. It was a short walk to a live-oak forest. His house was a former USMC barracks building. When I went back in the 1980s, there were expensive homes as far as the eye could see. Took all the fun out of it, and I’ve never gone back.
Hank, on the lovely charts and graphs, compare Hansen-Sato page 15. The H-S graph is showing the vast majority of a 5 meter rise as occurring in the latter half of the 21st century. I have no way of knowing the correct presentation, but to me that seems a more reasonable presentation of the how SLR will play out. Whether the final number is less than 1 meter or greater, graphs that show a pronounced take off in next few years look wrong to me. Hansen’s curve shape makes more sense. If there isn’t a certain number by 2017, I can just hear the blog hooting to call whole thing off.
Stefan, I am not a scientist, although I do have a background in the identification and measurement of risk. I just wanted to let you know after reading some of the comments on here and your responses that Job is being asked to return the award for patience since there is obviously a better candidate for the prize; you.
#91 Hank, I know some are shy to say this, but I don’t believe that mass transfers in the Gigatons have no effects on plate tectonics. At least I think so. As we “Humanform” the planet further it will be quite a different world. I read 36 gigatons a year from glaciers to oceans.
Mr. Davidson wrote expressing his concern that ice melt might affect plate tectonics. I doubt this is the case because movements of plates on the order of centimeters a year such as cause the Boxing Day earthquake a decade ago or the Sendai more recently represent far larger momenta and energies than are involved in either ongoing isostatic rebound from the last glacial maximum or the effects of current ice melt. I fully expect India to keep invading Asia for example, as she has through several stades.
@ 79 Hank quoting Orrin Pilkey ““Of all the various anticipated impacts of global climate change, sea level rise will likely be the first to produce a human catastrophe on a global scale….”
Not at the snail’s pace predicted here. Climate disruption is coming on much faster. Floods, droughts, heat waves, that sort of thing. Then ocean acidification. Then no food for a billion people. Fossil fuel profits high though.
Comment by Pete Dunkelberg — 17 Jul 2011 @ 5:26 AM
You are correct about the plate movements, but the triggers to release the stresses are another thing. Re-distribution of the mass will cause changes in the temporal patterns of earthquakes, not where they occur.
Unfortunately, sea level rise is not going to be a gradual thing. We will see big impacts when coastal storms occur, so the damage to property will not be a gradual thing but a sudden thing.
SecularAnimist #85, you are quite right that sea level rise is just one of a number of potential impacts due to AGW, and not the most short-term urgent one. Yet when you say “which makes it hard for me to get worked up about …” I think you fall victim to an optical illusion.
It is the same optical illusion that those people fall for that think it is enough to bring emissions to zero in order to stop AGW; of course it isn’t, that will only stop the rise in atmospheric concentrations, and temperature. With sea level it is one level worse still: even stopping the rise in temperatures will not stop sea level rise, only make it continue indefinitely, humanly speaking forever. It’s like the tired old metaphor of an ocean liner heading for an iceberg taking a long, long time to change direction.
Now, while it unfortunately is impossible to rule out a calamity in the near term that would completely wipe out civilization, I don’t think we should base our planning on assuming this: there likely will we a human civilization over the remainder of this century, fighting a witches’ brew of climate and other impacts on a resource-depleted planet. Major sea level rise will be one more ingredient, and one which at that point in time can no longer be usefully mitigated. That we should have been doing now.
There seems an ongoing scientific debate concerning the potential loss of the Arctic sea ice: On the one hand the general consensus seems to be that we will see seasonally ice free Arctic waters by 2030 – 2050. On the other we have, for instance, Wiesław Maslowski predicting 2016.
It’s my understanding that the magnitude of sea ice volume and extent losses we’re currently seeing in the Arctic are not predicted by the consensus GCMs — or at least not for a couple more decades — isn’t this an indication that these GCMs have underestimated a positive feedback or overestimated a negative feedback?
… dramatic perturbations of
summer sea!ice cover in the Arctic are reversible on very
short time scales of typically two years. This suggests that a
so!called tipping point, which would describe the sudden
irreversible loss of Arctic summer sea ice during warming
conditions, is unlikely to exist.
If the work of Tietsche, et al is based on models that are currently unable to adequately model the past 15 years of rapid volume and extent loss, can these models be relied upon to predict whether the ice can recover (short timescales or not)?
You replaced a poor analysis with another poor analysis. How to estimate velocities and accelerations in time series data is described in “Functional Data Analysis” by J.O. Ramsay and B. W. Silverman. Two of the key references are by Th. Gasser et al, 1991a, 1991b. There is much more primary literature. Code is available and is described in “S+ Functional Analysis User’s Guide” by D. B. Clarkson, C. Fraley, C.C. Gu and J.O. Ramsay.
Comment by Septic Matthew — 17 Jul 2011 @ 12:13 PM
> can these models be relied upon
“All models are wrong; some models are useful”
Different models, different results:
D Bernie, JA Lowe… – Progress in Physical …, 2011 – ppg.sagepub.com
… Concerning reversibility of Greenland ice-sheet loss, one model study incorporating a detailed ice-sheet model has found evidence for multiple stable states, representing effectively irreversible loss, even if global climate returns to its pre- industrial state (Ridley et al., 2010)….
It’s my understanding that the magnitude of sea ice volume and extent losses we’re currently seeing in the Arctic are not predicted by the consensus GCMs — or at least not for a couple more decades — isn’t this an indication that these GCMs have underestimated a positive feedback or overestimated a negative feedback?
Purely amateur comments, but my impression is that many think that improving modeling of Arctic sea ice trends is mostly a matter of getting a *lot* of details right.
For instance, this paper from 2006 compares Arctic cloud characteristics from three different models with each other (and with in situ observations) seeking to understand how the cloud characteristics influence the sea ice:
A different sort of study is undertaken in the following paper–meticulous in situ measurements are made in order to derive better values for the transmission of solar radiation through the sea ice. The idea is that the previous values–based on a similar, but smaller and presumably less accurate study done in the late ’70s–are biased low, leading to a systematic underestimate of the amount of energy reaching the Arctic Ocean through the ice. (Possibly explaining why the sea ice is declining faster than the models had forecast? The authors don’t make that claim in the paper, but it seems an inescapable inference.)
Interesting thread abou communicating Climate Science over at Judith Curry’s Climate, etc blog. One commenter even taking an amusing swipe at this place;
“If climatology wants to be a grown-up science, it should foster skepticism instead of ducking it. Every time a climatologist or IPCC’s house organ, realclimate.org, points a gnarled finger at a skeptic, a denialist, a hack in the pay of Big Oil and coal, a Republican, or an unpublished ignoramus, climate science depreciates in the public eye.”
“Every time a climatologist or IPCC’s house organ, realclimate.org, points a gnarled finger at a skeptic, a denialist, a hack in the pay of Big Oil and coal, a Republican, or an unpublished ignoramus, climate science depreciates in the public eye.”
My response is Judith Curry and Republican eyes should be more open to science:
NE passage about to be open very early this year, not according to the skeptic plan, was it suppose to be regaining its extent? Cooling? Not following an ignorant skeptic rant? Are they, the contrarians magicians? Do they expect climate to behave according to their political agenda?
Hank and Pete, on the facts the contrarians have lost their cause a long time ago. Its now their strategy to turn climate in a purely partisan debate which has a chance to win because they channel money in the pockets of expert manipulators who do nothing else. World wide global temperatures are rising = sea ice vanishing = glaciers melting . If we remove ourselves from the equation, and present the facts vividly, it does not matter what they do or say.
It makes perfect sense that an acceleration in surface warming should cause a more rapid rise in sea level, due to both greater land-locked glacial melt and ocean thermal expansion. However the temporal response of both effects would seem quite complex (eg, the relative contribution of mountain glaciers versus ice sheets; rate of warming at different depths/tempratures in the ocean), and further complicated by issues like water mining and water storage in reservoirs. I note that Vermeer & Ramsdorf predict acceleration in sea level substantially greater than the IPCC AR4 predictions, and as best I can estimate from figure 6 in the paper, V&R project a rate of sea level rise of ~ 0.59 cm per year by 2020, and ~0.74 cm per year by 2030.
The satellite sea level record (1993 to present) shows a rate of ~0.31 cm/year, but with no obvious acceleration over the 18 year period. Two questions: Do you think the satellite record is accurate? Do you expect the trend in the satellite data to begin accelerating soon?
Comment by Steve Fitzpatrick — 18 Jul 2011 @ 1:02 PM
> substantially greater than the IPCC AR4 prediction
The real key here is that, as you focus more on the most recent data, the estimates of “acceleration” become less and less reliable: the short-term variation swamps any estimate of acceleration. You see this as well in the broad confidence band in the posted graph Only by cherry-picking can you detect any acceleration of sea level rise.
Comment by Septic Matthew — 20 Jul 2011 @ 11:56 AM
Tilo-san: unfortunately Barton was wrong. I used monthly data that came up to date, Barton used yearly data that didn’t. For some inexplicable reason Barton seemed to think that trending yearly data was more accurate than trending monthly data.
Me: If you let me use data sampled at the one-second level from 6 AM to 9 AM here in Pittsburgh, I can prove that the seas will boil in a few weeks. It’s appropriate to time-sample on scales consistent with the data being examined. For global warming, the proper sample size is 30 years or more. Annual data is fine for that. Chopping it up into months artificially balloons your significance (see the morning experiment proposed above).
Your 2007 model assumes that sea level rise is a function of the temperature difference between the present period and a base period. In the current decade temperatures have not decreased, so one would expect that sea level rise should have continued at the same rate. In addition things like La Nina have to do with ocean temperatures which would affect Steric sea level rise, but would not impact volume changes. So the fact that sea level rise throughout the last decade is below the levels predicted by your models is interesting. You can reasonably argue that this is short term variation.
I would argue that this period is the first true out of sample test for your models. As so often happens in this types of things the most difficult time to predict is the future. We both know how often models are created based on historical data that immediately fail in current periods. So far this is happening with your model, but only time will tell whether this is a short term problem.
I know you attempted out of sample testing in your 2007 paper, but as I pointed out in an earlier article it didn’t really work out.
Comment by Nicolas Nierenberg — 21 Jul 2011 @ 12:27 PM
#75 tph “in order to get 1000 mm by 2100, that is an average of 10 mm/yr for the century – that means a significant acceleration is to come”. Why doesn’t this just beg the question? You infer that “a significant acceleration is to come” from your assumption that predicted sea levels for 2100 are already set in stone. Says who?
simon asks:”#75 tph “in order to get 1000 mm by 2100, that is an average of 10 mm/yr for the century – that means a significant acceleration is to come”. Why doesn’t this just beg the question? You infer that “a significant acceleration is to come” from your assumption that predicted sea levels for 2100 are already set in stone. Says who?”
The best available research and the apparent ostrich head in the sand approach to dealing with unpleasant realities, so that business as usual is going to be the “plan”. The sea level data over the past century has a signal to noise ratio that is too high to detect any changes in acceleration over the past 130 years, mainly because the driving force is too weak compared to natural fluctuations and the observations too poor for most of the time period. By mid century both of these factors will be such that we may even analyze the third derivative of global sea level.
#121 tph “By mid century both of these factors will be such that we may even analyze the third derivative of global sea level.” Again, to what other evidence do you cross-refer to make such a confident prediction?
A report published in JCR by Watson shows that sea levels are decelerating in Australia and New Zealand. The report is based on tidal records going back from 1897 t0 present (Fremantle Western Australia), 1903 to present (Auckland NZ), 1914 to present (Sydney Australia) and Newcastle (NSW Australia). This seems to support the findings of Houston and Dean
Beware the newspaper’s spin. The story refers explicitly to H’n'D, it’s not saying Watson made the comparison. Further down they mention that Watson has twice told them something — but whatever he said didn’t make it through to the article clearly enough to understand. Wanta bet the newspaper’s wrong?
Below the story, the first comment on that page says:
“This is a complete misrepresentation of Phil Watson`s views. See for example the Pittwater Council`s website.”
Hank is correct, at a science site like this we should be looking at the research paper published by Watson, not a newspaper story about it.
The Watson paper is at http://www.jcronline.org/doi/full/10.2112/JCOASTRES-D-10-00141.1
It looks like a reasonable paper to me, with quite a fair literature review.
He looks at the 3 sites in Australia and one in New Zealand with continuous tide gauge records for at least 80 years. They show a very slight deceleration.
IA, as Gavin says, the cherry pick is the same as in H&D, and so is the refutation: see above. The same model that we used in our 2009 paper to describe sea-level rise as a simple function of global temperature for the past instrumental period — and which projects the “comparatively large” sea level rise values out to 2100 that H&D have a problem with –, has no difficulty at all reproducing also the near-zero “acceleration” for 1930-now (or 1940-now) noted by H&D. There is no contradiction.
The thing I dont really understand is why the authors fit a simple quadratic when there is a discontinuity in the data from the 1960′s/70′s onwards. The weight of earlier data in the series means you get a good r-squared but to then say the the rate of change is declining seems…odd?
The article in the Australian does seem to accurate portray Watson’s paper. The following quotes are taken directly from the journal:
‘the analysis finds there was a “consistent trend of weak deceleration” from 1940 to 2000.’
‘Mr Watson’s research finds that in the 1990s, when sea levels were attracting international attention, although the decadal rates of ocean rise were high, “they are not remarkable or unusual in the context of the historical record at each site over the 20th century”.’
‘He said further research was required, “to rationalise the difference between the acceleration trend evident in the global sea level time-series reconstructions (models) and the relatively consistent deceleration trend evident in the long-term Australasian tide gauge records”.’
“I refer to today’s article titled, Sea-level rises slowing: tidal records.
Your article has misrepresented our Mr Phil Watson’s research paper by saying that ‘global warming is not affecting sea levels’. This is untrue and misleading and it is not what Mr Watson told your journalist. Mr Watson’s research looked only at measurements of historical data. It specifically did not consider predicted linkages between sea level rise and global warming predicted by climate models….”
Click the link for the full text.
Comment: Looks to me like this is the agency responsible for protecting heritage sites along the coastline, which has to decide when and where to protect or move structures as sea level changes. They are interested in site-specific numbers for their local responsibilities.
“All indications, from the Arctic and worldwide surface temperatures, melting and movements of the Greenland/Antarctica ice sheets perimeters, Arctic and worldwide sea surface temperatures, Arctic sea ice extents/areas/volumes, atmospheric CO2 concentrations and the oceans (limited and apparently reduced) capacity to uptake these increased CO2 concentrations in a warming climate…”
Using, you guessed it, their quadratic relationship, which has absolutely no physical science basis whatsoever.
They then go on to use this exercise (no make that excuse) in curve fitting “model” to extrapolate from 2010 to 2100 for several locations in Florida.
Curev fitting ~90 years worth of data and then extrapolation ~90 years from this dubious exercise in statistical math… (using OLS, no less, when the time series are quite clearly of a non-stationary nature).
Words can’t describe what these two are doing to the field of science.
The latest IPCC panel on ocean rise is deliberating their predictions. I noted that they stated that at this time in the last interglacial the worlds temperature was 2C hotter and the oceans 6 metres higher. This seems like a contradiction as it is meant to be mankind that will cause this problem, yet it happened before according to the scientists at the IPCC. Gavin do you have an explanation for this contrary information.
Comment by Pete Dunkelberg — 23 Jul 2011 @ 8:17 AM
Mike M. asks:”Re #33, “…we favor relating sea level to temperature, not time)”
Okay but then come up with a definition of what such a math result represents because that AIN’T ‘acceleration’ in anybody’s vernacular.
The whole basis of climate prediction itself is founded on the principle of what will happen IN TIME, no?”
No. Climate prediction is based on physics. The assumptions are that humans will continue to emit CO2 in the future, which has the first order physical effect of raising temperature. The reason for relating sea level to temperature is because most sea level rise is caused by increased temperature. Temperature, while having an underlying trend upwards (because of the unrelenting increase in CO2 which causes increase in temperature) has a noise component. The same factors that add noise to temperature adds noise to sea level.
141, Mike M. The whole basis of climate prediction itself is founded on the principle of what will happen IN TIME, no?
No. Some of the statistical models are based on the analysis of time series. The physical models predict temperature change as a result of CO2 change. These latter are the models relevant for assessing changes in the energy economy and reforestation. Time enters these models because of the rate of change of CO2 concentration.
Going slightly OT for a minute, I just had a look at Sivan 2004 and Lambeck 2004 – both archaelogical studies of past sea level. Results from both are depicted in Kemp et al. 2011, Fig.3 but I’m wondering if they’ve been incorrectly plotted.
In the two papers figures are given as ‘before present’ (BP) for reference. By convention I think ‘BP’ = ’1950′ but the plot in Kemp et al. appears to use 2000 as the ‘present’ reference point instead which moves everything upwards by about 10-15cm.
Neither the Sivan or Lambeck paper explicitly define ‘BP’ as ’1950′ so I could be wrong about this but I’ve been reading a bit about past sea levels and this apparent discrepancy was a source of confusion. For Stefan, Martin or Mike, I realise you probably wouldn’t have worked on this part of the paper but do you have any idea whether or not my interpretation might be correct?
If global sea levels are rising due to thermal expansion, may we not reasonably conclude that the planet’s diameter is increasing? Basic physics tells us that as the diameter increases, the rate of rotation will slow in order to conserve angular momentum. This affects the length of day and can be measured to a very high degree of precision.
I am quite aware that tectonic plate movements, changes in ocean currents, as well as astronomical influences can and do affect the Earth’s rate of rotation but these are reasonably well understood and can be calculated.
Looking at records of the changes in length of day since 1860, e.g. here [http://www.john-daly.com/press/lods1860.gif] it’s clear that there is no discernible trend which would suggest long-term or accelerating increase in the Earth’s diameter.
The change in diameter due to thermal expansion is way down in the noise. What is measureable, though, is the change in the Earth’s oblateness due to redistribution of mass from the Greenland and Antartcic Ice Sheets – mass from near the axis or rotation is distributed around the Earth. See, for example:
Nerem, R. S., and J. Wahr (2011), Recent changes in the Earth’s oblateness driven by Greenland and Antarctic ice mass loss, Geophys. Res. Lett., 38, L13501, doi:10.1029/2011GL047879.
There is a bit more background on this in:
Munk, W (2002), Twentieth century sea level: An enigma, PNAS, 99, doi:10.1073/pnas.092704599
Mitrovica et al. (2006), Reanalysis of ancient eclipse, astronomic and geodetic data: A possible route to resolving the enigma of global sea-level rise. Earth Planet. Sci. Lett. , 243, 390.
ps, anyone know of anything more recent along this line? http://www.sciencemag.org/content/297/5582/831.short
Science 2 August 2002:
Vol. 297 no. 5582 pp. 831-833
Detection of a Large-Scale Mass Redistribution in the Terrestrial System Since 1998
148 Scottie said about changes in earth’s rate of rotation.
If you can calculate all the stuff you said you could calculate why didn’t you calculate the change in the earth’s moment of inertia due to a 3mm/year sea level rise? To make it easy, assume that all that rise is due to thermal expansion of the oceans. The oceans are about 1/10^4 of Earth’s mass. The annual fractional change in the earths radius due to a 3mm sea level rise is about 1/10^9 . Thus the change in the moment of inertia due to rising seas under the assumption that it is ALL thermal expansion is about 1 part in 10^13 /year. After 100 years that is a part in 10^11 change. A day is about 10^5 seconds. The change in the length of the day is thus going to be on the order of microseconds. Your graph shows millisecond time scales. With all the other noise in the system you are unlikely to be able to see this. Especially since not all of the rise increases the moment of inertia; the rise due to glacial melt would decrease the moment.
Comment by John E. Pearson — 24 Jul 2011 @ 11:47 PM
I think you’ll find that the length of day is increasing very slightly but it has little to do with any changes in the diameter of the earth. Rather, it is due to tidal acceleration within the Earth-Moon system.
Comment by Bill Woolverton — 25 Jul 2011 @ 1:01 AM
The simple law of physics is that the Earth’s rotational velocity varies as the inverse of its radius.
A rise in sea level by 2100 of 59cm (IPCC) or 20 feet (Al Gore) would result in an easily measurable increase in length of day, and that trend ought to be detectable by now.
Does anyone here know of a length of day study where this has been confirmed – or otherwise?
Scottie, Scottie, Scottie… the formula for the moment of inertia of a sphere with changing radius does not apply. What happens is that a very thin film on the surface of the sphere gets a little thicker, an effect of an entirely different magnitude.
Here is (h/t Neil White) Walter Munk’s great paper, which should give you a feel for the magnitudes involved. Unfortunately Jerry Mitrovica’s follow-up paper is nowhere freely available, but here is a great talk by Jerry that touches upon it.
Scottie. I recommend you pick up an undergraduate physics text. There is no such law of physics as: “The simple law of physics is that the Earth’s rotational velocity varies as the inverse of its radius.” The simple law of physics that you are trying to discuss is that angular momentum is conserved: I omega = constant, where “I” is the moment of inertia and “omega” is the rotational frequency. As I pointed out above, THe change in “I” due to a 3 mm per year rise in sea level (under the assumption that the entire 3 mm comes from thermal expansion) is about one part in 10^13 and consequently, over a century the cumulative change in the length of the day would be about a microsecond. To estimate “I” as I did above we write:
I_earth = I_solidball + I_ocean
I_solidball ~= M_ball R^2
I_ocean = M_ocean R^2
where M_ball is the mass of the earth without it’s oceans) and M_ocean is the mass of the ocean. Note that M_ocean ~= M_ball/10000 . R is the earths radius. If the oceans expand an amount dR=3mm, the change in I_earth will be due to the change in I_ocean, not in the solidball part. If the ocean’s expand dR, the new moment becomes:
Note that the solidball contribution to I_earth does not change. This is why your argument fails Scottie.
The fractional change due to the ocean expansion compared to the total is
2 dR/R M_ocean/M_ball ~= 1/10^13. After a century this would result in a change in the length of the day of about a millionth of a second. Given all the other sources of the change in the length of the day this is not observable.
Comment by John E. Pearson — 25 Jul 2011 @ 8:25 AM
Scottie: Al Gore’s 20 feet figure is not related to any specific time-frame.
The thing about sea level rise is that we are very uncertain about how fast it will happen, but we can be absolutely sure that it will happen. It’s basic physics.
If you wish to persist with your “it’s not rising” idea, then please will you calculate for us what change to the day length you expect to see for the currently observed sea level rise?
“A rise in sea level by 2100 of 59cm (IPCC) or 20 feet (Al Gore)”
Nowhere does Gore say that sea level will rise by 20 feet by 2100. He never put a date on it, only that it would happen if the Greenland ice sheet and the West Antarctic ice sheet melted. And, as Martin points out in #157, there would be no detectable change in length of day.
157, MartinVermeer: What happens is that a very thin film on the surface of the sphere gets a little thicker, an effect of an entirely different magnitude.
And it gets less dense at the same time, further reducing the effect.
Comment by Septic Matthew — 25 Jul 2011 @ 10:38 AM
Hi, the thermal expansion leads to only a very, very small increase of I_earth as shown above. This is due that only the ocean water expands but not the inner of earth.
But the the increase of I_earth due to the melting land based ice near the rotational axis and the redistribution of melt water into the ocean is much greater, and has been already measured, see http://www.skepticalscience.com/Bulging-at-the-waist.html
John E. Pearson #158, a good order-of-magnitude estimate, but in fact it’s a little more complicated. First of all you assume that the ocean expands homogenically, i.e., the whole ocean mass moves outward from R to R + dR. In reality of course the bottom of the ocean remains in place and so does the water touching it, so the mean movement of the ocean is only half of this, R -> R + dR/2.
…but not even this is enough: a large part of the actual thermal expansion takes place mostly in a rather thin tropical surface layer, not the full ocean depth. And we haven’t yet talked about horizontal (latitudinal) water movements…
Looking at melting ice sheets, you get much bigger effects. This is because actually (to first order) M_ocean changes; by a fractional amount of dR/D, where D is mean ocean depth.
2 dR/R M_ocean/M_ball ~= 1/10^13. After a century this would result in a change in the length of the day of about a millionth of a second.
I find that a relative change in rotation rate of this magnitude gives, for a day ~= 10^5 s, 1/10^8 s or 10 nanoseconds in length-of-day. After a century (~40,000 days) it builds up to 0.4 ms. The ice sheet effect would be a factor ~1000 larger, order 0.01 ms in LOD, cumulating to 0.4 s. A tall order to detect, but this is for 3 mm only.
Comment by Martin Vermeer — 25 Jul 2011 @ 11:13 AM
Well the 2nd reply to H&D is now open access as well as a 2nd H&D reply, also a 2nd H&D JCR paper is now open access and deals with the 18.6 year lunar nodal tide and its potential effects on SINGLE tide gage records of varying record lengths;
It would appear that H&D seem only concerned with the past up to the present day, but are not willing, at all, to consider other data sources or future outcomes of a warming climate in the 21st century. Go figure.
However, H&D do finally admit the existence of Church & White (2011) that RV mentioned in their earlier reply, but only in passing and very briefly, with this cherry picked quote;
“Church and White (2011) note that the rise measured by the altimeters is not statistically different than peaks in trend in the 1940s and 1970s.”
Give me a break H&D, put both of your JCR papers next to Church & White (2011), it’s like Amateur Night at the Apollo, by comparison.
AFAIK, the 18.6 year nodal tide has little to no effect on area weighted global estimates of SLR using all available tide gages and altimetry data available for making said GLOBAL estimates of SLR. But, I’ll gladly stand corrected if this is shown not to be the case.
MArtin, DOesn’t the ice sheet stuff go the wrong way? Anything that flows into the ocean decreases the moment of inertia rather than increases it. That’s why I ignored it, besides it being complicated. I have no idea as to whether the sign of the overall change is even positive. I think a microsecond per century is a decent upper bound, no?
Comment by John E. Pearson — 25 Jul 2011 @ 2:08 PM
I am particularly grateful to Neil White (#150) for pointing me towards Walter Munk’s excellent paper “Twentieth century sea level: An enigma”. This is exactly the sort of thing I was hoping to find.
I see no point in engaging with those commenters who deny the laws of Kepler and Newton, nor will I be side-tracked by responding to condescending remarks, but thanks to everyone else for your responses. And yes I agree, let’s forget about Al Gore. He is a bit of an embarrassment!
[My bold throughout]
Munk starts by outlining a problem with estimates of current sea-level rise, and one of the constraints on one possible explanation is that “severe limits are imposed by the observed perturbations in Earth rotation.”
“The Intergovernmental Panel on Climate Change attributes about 6 cm!century to melting and other eustatic processes, leaving a residual of 12 cm of 20th century rise to be accounted for. The Levitus compilation has virtually foreclosed the attribution of the residual rise to ocean warming (notwithstanding our ignorance of the abyssal and Southern Oceans): the historic rise started too early, has too linear a trend, and is too large. Melting of polar ice sheets at the upper limit of the Intergovernmental Panel on Climate Change estimates could close the gap, but severe limits are imposed by the observed perturbations in Earth rotation. Among possible resolutions of the enigma are: a substantial reduction from traditional estimates (including ours) of 1.5–2 mm!y global sea level rise; a substantial increase in the estimates of 20th century ocean heat storage; and a substantial change in the interpretation of the astronomic record.”
“This paper does little toward solving the problems of the historical rise in sea level. In looking for causes, I have applied what Edward Bullard (31) has called the “Sherlock Holmes procedure” of eliminating one suspect after another. The procedure has left us without any good suspect (it is a matter of attribution, not of error bars), but I am reluctant to accept large error bars as definitive evidence for dismissing the traditional estimates of 1.5–2 mm!y for the 20th century sea level rise. Thermal expansion was the candidate of choice at the time of the first IPCC review. This choice has been almost foreclosed as a major factor by the recent compilations of Levitus and by recent model calculations that account for the incremental ocean heat storage as a consequence of greenhouse warming. The computed steric rise is too little, too late, and too linear. The rotational evidence, although convoluted, appears to rule out a large eustatic contribution from melting on Antarctica and Greenland, assuming that the measured ˙J2 is representative of the 20th century. However, an enhanced contribution from glacial melting and other midlatitude sources is NOT ruled out by the rotational evidence.”
So it would appear that variations in the Earth’s rotation are very much a part of the equation. Now we need to know whether any sustained increase in LOD has been observed in recent years, as this could be an indication of accelerating sea-level rise. This is a fascinating subject.
If anyone knows of more recent papers, I would be very interested in reading them.
Comment by John E. Pearson — 26 Jul 2011 @ 10:46 AM
Hope this is not OT
The ‘sceptics’ have now moved onto to a paper that they say claims that sea levels started rising before 1800 (Jevrejeva, S., J. C. Moore, A. Grinsted, and P. L. Woodworth (2008), Recent global sea level acceleration started over 200 years ago?, Geophys. Res. Lett., 35, L08715, doi:10.1029/2008GL033611. and Jevrejeva, S., A. Grinsted, J. C. Moore, and S. Holgate (2006), Nonlinear trends and multiyear cycles in sea level records, J. Geophys. Res., 111).
The authors apparently used data tidal gauges in Amsterdam, Liverpool and Stockholm.
The ‘sceptics’ are using this to claim sea level rises started before industrialisation could’ve had an effect.
Any comments or suggestions? It could be that the ‘sceptics’ just switch attention fast.
PS. I’m not going to give the ‘sceptic’ website as I don’t feel obliged to help them with any advertsing beyond the above…. unless people here want it
My thanks to Martin Vermeer (#172) – I do appreciate your guidance in finding the Mitrovica et al. 2006 paper. I’ve also found time to study the Munk paper, postings and comments here at RC – and papers by Nils-Axel Mörner (yes, I know!)
Complex as the understanding of interchange of angular momentum between the Earth’s core, lithosphere, hydrosphere and atmosphere over geological time scales undoubtedly is, I still come back to my initial simple observation that: “as the diameter [of the planet] increases, the rate of rotation will slow in order to conserve angular momentum.”
Both Munk and Mörner suggest that thermal expansion of the oceans is a less important factor in sea-level rise, especially over short/medium time-scales. But the proposition is that sea-levels are rising, and the rate is accelerating. What could be the reason?
Well, melting polar ice must be a prime candidate. Munk suggests:
The eustatic sea level rise from melting of polar ice sheets is associated with a movement of water mass away from polar regions and so is opposite to the earth rebound. A eustatic global rise by 1 cm is associated with an increase in the lod by 0.1 ms.
Martin Vermeer (#171) makes a very similar point in response to John E. Pearson (#167)
Modern apparatus such as an atom interferometer gyroscope can measure the Earth’s rotation with an accuracy great enough to confirm Einstein’s general relativity, so detecting an increase in LOD of around 0.1ms or even an order of magnitude less should be a walk in the park. Has this been detected, and if not what is the explanation?
Finally, for the tetchier commenters here, please be assured that my comments are not motivated by anything other than a desire to understand the science behind current sea-level rise.
> Has this been detected, and if not what is the explanation?
Scottie, there are many other things that affect the Earth rotation on much shorter than geological time scales: tidal friction from Sun and Moon, and variations in angular momentum of the non-solid components of the Earth, like atmosphere and ocean. The only way to remove these, and find the “clean” change in LOD due to moment-of-inertia change, is by modelling them. And while this modelling is pretty good, it is not perfect. Yes, there are great technologies nowadays for measuring Earth rotation, but this is a fundamental limitation the battle against which is uphill. That being said, as the Munk and Mitrovica papers show, 20th century sea-level rise actually shows up in this data.
Now, as we are really interested in the moment of inertia, there is another technique: monitor the dynamic form factor J2 of the Earth’s gravitational field (which is related to the moment of inertia around the rotation axis) directly using laser ranging to satellites, as was referred to by Uli.
BTW Mörner’s papers from before the sad mystery event may well be OK :-)
#174, Jeremy C – Jevrejeva 2008 is a tide gauge sea level study reaching back to 1700. They fit a polynomial curve to the resulting record and find the lowest point (trough) occurs at around 1770, hence ‘accelerating for over 200 years’.
However, there is only one tide gauge station before 1768 and only three before ~1850, all situated in North-Western Europe. Given the lack of spatial diversity the small upward trend in the record before 1850 could easily be regional rather than global.
The recent Kemp et al. 2011 paper shows a comparison chart featuring various paleo-sea level data. Some of these do corroborate the idea of the uptrend beginning in the early nineteenth century but again the data is quite spatially-homogenous.
It’s plausible but really the trend is quite small up until the mid-to-late nineteenth century however you look at it.
Thanks for all the suggestions for my reading list!
I have now studied (amongst others) papers by Nerem and Wahr (2011) and by Botai and Combink (2009), also the recent paper by Zwally & Giovinetto (2011), who challenge some assumptions and identify the uncertainties inherent in the three techniques used to estimate polar ice loss. Their re-analysis puts ice loss from Antarctica at the lower end of most current estimates.
For anyone interested in possible changes in LOD due to sea-level rise, the IERS site holds invaluable records and easy to understand descriptions of the various factors affecting the Earth’s rotation.
Greenland ice sheet mass balance: distribution of increased mass loss with climate warming; 2003-07 versus 1992-2002
Authors: Zwally et al.
“… The net balance changed from a small loss of 7 ± 3 Gt a-1 in the 1990s to 171 ± 4 Gt a-1 for 2003-07, contributing 0.5 mm a-1 to recent global sea-level rise….”
Hank Roberts (#182): Yes thanks, I did see that paper. It seems to agree broadly with other estimates of Greenland ice loss. It seems that although the Greenland ice sheet is gaining mass inland, it is losing mass round the coasts, resulting in a net loss.
But I found the the Zwally and Giovinetto paper particularly interesting because of its attempts to identify and quantify the uncertainties.
> And that preferably does not require adjustments for glacial isostatic adjustment.
But it does…
The real problem though is the disentanglement from the effects of atmospheric angular momentum variations and lunisolar ocean tidal friction, which require disgustingly detailed modelling… no way is this a clean observable. And VLBI is already a very good direct technique.
Sorry for my sloppy terminology. When responding to Didactylos’s comment about “direct measurements” I confess I was thinking of tide gauges. Of course GIA must be corrected for in LOD measurements, but isn’t that a global correction, unlike the individual local corrections for each and every tide gauge. I mean, would the GIA correction for a tide gauge in (say) Iceland be the same as that for one in (say) Hong Kong? Could this be a source of error or uncertainty?. Or have I got this completely wrong?
According to IERS, many irregularities of the Earth’s rotation are already well understood, e.g. Polar Motion (Chandler wobble), Celestial motion of the pole, variations due to the zonal tides, atmospheric circulation, internal effects and the transfer of angular momentum to the Moon orbital motion.
Is it really so difficult to detect the expected increase in LOD due to sea-level rise? Perhaps it is.
In a 2007 interview by EIR, Dr. Nils-Axel Mörner (yes, I know) said about sea level rise:
“Yes, it might be 1.1 mm per year, but absolutely not more. It could be less, because there could be other factors affecting the Earth, but it certainly could not be more. Absolutely not! Again, it’s a matter of physics. So, we have this 1 mm per year up to 1930, by observation, and we have it by rotation recording. So we go with those two. They go up and down, but there’s no trend in it; it was up until 1930, and then down again. There’s no trend, absolutely no trend.”
So, let’s see, a decrease in LOD of 0.12ms over a time span of 200 years works out to -0.6 µs/yr (on average).
So, should I plot this as a linear trend or a quadratic trend?
I would guess quadratic IF the resulting quadratic trend line were actually observable (measurable) in nature.
If all of this is assumed to be purely quadratic (e. g. deceleration), we’d start out at a rate of 0.0 µs/yr and end up at a rate of -1.2 µs/yr (which, you guessed it, yields an average of -0.6 µs/yr).
At the 100 year mark, we would have a decrease in LOD of -30 µs and a rate of -0.6 µs/yr.
So let’s plot this one (-6 µs/yr (on average)) next to this plot;
I suggest that you ask Nils-Axel Mörner where he gets this from. He’s retired, but still (I think) has a web site and an email address. Good Luck! If you get a coherent answer please share it with the rest of us!
I also suggest that you critically read the whole of that interview (and have a good look at the photograph of the tree).
Hank Rpberts (#186) – Thanks for the link to the IERS Technical Note. It would appear that the 1998 J2 anomaly will be exercising minds for a while yet.
I am aware of the problems with Mörner’s claims. I mentioned him only because he proposed that it was definitely possible to infer sea level rise from measured changes in LOD, and claimed to have done so.
I won’t bother you again with troublesome assertions or questions. I’ve finally come across a paper which answers my original point pretty well. Landerer, Jungclaus and Marotzke (2009) propose a mechanism whereby, even in the mid range of IPCC scenarios, the small variations in Length of Day and Polar Motion induced by sea level rise, can produce small but not insignificant changes in Earth Orientation. Of course, precise Earth Orientation data are vital for spacecraft navigation, etc. The paper also suggests that Earth orientation observations can give an independent verification of global sea level rise.
“In order to characterize peer-reviewed literature with sea level rise projections to 2100, we completed two searches in the ISI Web of Science. The first was the Boolean search `sea’ and `level’ and `rise’, which returned 5332 articles. The second was the Boolean search of `sea’ and `level’ and `rise’ and `2100′, which returned only 107 articles. These 107 papers then became our sample for appraising the scientific literature. A large number, 76, of these papers stick to the sea level contribution from their authors’ particular expertise (e.g. thermal expansion) and time-scale (e.g. past sea level rise or current sea level rise rates), but quote the IPCC projections. These were not retained in our data set because they are not giving an independent projection. There were six papers that give sea level rise projections for a doubling of CO2 and are from the time when the IPCC was focusing on a doubling of CO2 as a metric rather than conditions in 2100. Therefore, 25 peer-reviewed papers out of the original 107 remained, to enable us to show a global sea level rise to 2100 from either one source (e.g. ice sheet melting) or all sources. The papers that included all sources of sea level rise were climate modeling studies….”