Query? The greenhouse melting was bound to occur, with or without man? Am I interpreting the ice core data wrong? It seems the glacial cycle is lengthening mainly because each cycle sequesters more carbon into the crust, and this net fixing of carbon from cycle to cycle lengthened by 10,000 years the period of last two cycles. (Is this my theory alone?)
We all complain about oil burning because oil is sequestered carbon.
Re #1 (Matt): It is well-accepted that Milankovitch cycles (the combination of three kinds of orbital perturbations – roundness of orbit, degree of axial tilt and precession of the axis, if I recall correctly) essentially control the timing of the glaciations. Noting that carbon also comes out of the crust via volcanism, I haven’t seen any scientific claim that somehow the amount of available carbon is declining in a manner that would control glaciations. In any case the interglacials are not in any kind of consistent decline in length, and the Milankovitch cycles do seem to sufficiently explain the observed changes. That said, it’s also clear that glaciations (which have not been present throughout much of history, with ice-free conditions existing as recently as 30M years ago and the current severe glaciations – the Pleistocene – having kicked in just a couple of million years ago) have not been able to exist in the past whenever CO2 has been above a certain level in the atmosphere. The complaint about the current pace of putting CO2 into the atmosphere is that we will rapidly reach such a level and that (among numerous other effects, the bulk of them unpleasant) part of the ice caps will melt, raising sea level by substantial amounts. Complete melting of the ice seems beyond our present reach, but maybe if we keep trying hard enough… :(
BTW, all of the carbon that is not active in the climate cycle (i.e., present in the ocean or atmosphere) is sequestered, even if not in the form of fossil fuel, so the fact of prior sequestration is part of what defines the problem. Oil is just one source — coal, gas, wood and peat are others.
The alarmist claim is a political one and nothing more. It’s a fogging of the issue and unfortunately always has a possibility of working. Keep after it Gavin. This fight is real. We want truth to prevail. I’m pretty sure the whole world does.
In some ways Lindzen’s thinking on the climate change issue has not changed much since 1999
Actually it’s been quite a bit longer than that; see for example his 1991 testimony. In it he discusses low climate sensitivity and the possibility of negative water vapor feedback. In fact he was writing about 2xCO2 climate sensitivity well before AGW got much attention. The origins of some of his ’91 comments are in an ’82 paper, although interestingly that paper seems to accept positive water vapor feedback and reports a climate sensitivity of just under 2K.
I hesitate to dismiss Lindzen because he seems to be a sort of modern Diogenes’ last honest climate skeptic. I’d love to see him get 10 grad students for 5 years to see what came out – though I suspect that like the Adaptive Iris (which he seems to have set aside for other pursuits) it wouldn’t work out.
I find it ironic that Lindzen is skeptical of climate science, but when he ventures into the policy arena, he uncritically accepts the far less scientific notion that emissions reductions are extremely costly.
Why, in the absence of man, are not the old growth forests part of the carbon forcing? During a 10,000 year hot, dry spell like we have, wouldn’t they have burned off? Isn’t the glacial period, right now, trying its best to oxidize whatever carbon it can peel back from the earth? The glacial cycle should be oxidizing enough carbon to get that ice melted.
I am still confused as to why the glacial drop in temperature is delayed, for it seem clear that we start the drop in temperature when reach the magic 6 degrees off nominal (mid glacial cycle). We should be seeing that by now, man or no man. Why hasn’t the ice caps melted yet? And better yet, what has held the CO2 levels so low for the past 10,000 years?
I am also confused that we do not recognize the lengthening of the glacial period as in:
where clearly the cycle seems to be taking longer and longer.
Why do we think the oxidation of land carbon is not the driver, perhaps not the pacemaker, but at least the amplifier? We are awfully hot and dry, and there is about twice the available carbon in plants and soil as in the ocean.
I guess, what I am driving at is this. The earth, at this part of the cycle seems awfully sensitive to carbon sources, the rise in CO2 levels have been delayed for so long. Are we really completely to blame, or have we just shifted short term carbon around, delaying and controlling oxidation (until 1950, that is).
I had thought that the actual difference in Milankovich forcing (between extremes) was much smaller then current CO2 et al forcing. Are Milankovich cycles seen as a trigger for postive feedbacks going into or out of glacial periods? But then, ice records show associated CO2 changes, but is this the chicken or the egg? In any case, how much can we learn about our current interglacial but getting warmer situation from looking only at the past millions of years of glacial/interglacial cycles? Glacial cycles are apparently associated with a drying and cooling of the atmosphere. It seems that a warmer world would be a wetter world, unlike Lindzens argument r.e. water vapor feedbacks.
From listening to Lindzen, it seems he believes strongly in stable equilibrium – the notion that a stable system will respond to stress in such a manner as to restore stability. This is still a valid scientific viewpoint, which could account for Lindzen’s credibility. Some systems (buffers, for example) display this behavior, but it doesn’t seem to apply to the climate system, which has many positive feedbacks (pebbles starting avalanches). The large swings of glacial cycles and sea levels in the absence of any human perturbation should suggest a relatively sensitive climate, especially if the glacial/interglacial switches occurred very rapidly (100-1000 years?).
Lindzen should consider that an honest approach to the problem involves openminded consideration of all possible forcings and feedbacks, not just those that happen to fit with one’s notions. Calling people ‘alarmists’ and suggesting they are trying to terrify the public into funding science is reducing a scientific debate to a political squabble. In any scientific area one can find a dissenting scientific opinion, whether you are talking about the K-T boundary and the extinction of the dinosaurs, quantum mechanical theories, or whatever. Generally, unless they have some startling new evidence, outliers to general scientific consensus are not handed bullhorns and invited to speak to Parliament.
I agree with Lindzen.When you consider the Ice Ages we know that the CO2 started climbing after the the temperature rose and fell after the temperature fell. Furthermore if the temperature was influenced by the CO2 as much as you claim then we would expect the temperature ( strickly speaking the 4th power of the temp in degrees absolute) to have risen faster as the CO2 increased: it didn’t.Moreover the CO2 increase accelerated as the temperature increased.
When the temperature fell the CO2 fell only slowly (perhaps because the biosphere used less). The scource of the CO2 was the sea and it was reabsorbed as the global temperature fell.
[Response: Errrm, you have a lot of this rather badly wrong. If you are getting your fourth power from R prop T^4, then its the other way round: T increases as the fourth root of radiative forcing. Just as well, really (though I suspect that for the relatively small perturbations we're in, the linearised version will do). But anyway, the radiative forcing isn't proportional to CO2 concentration, its proportional to its log - William]
If I eyeball the latest vostok ice core, I find the CO2 data correlates well on the rising slope of the cycle, but lags on the falling slope. Peaks in temp seem to correlate with simultaneous peaks in CO2, indicating, to my untrained eye, that CO2 dominates heating but ice melt dominates cooling.
I have a hard time understanding that slight orbital changes in sun angle could cause such a rapid rise in temperature.
Where would all that CO2 come from, the oceans being so cold? From the rotting of dead biomass near the tropics, I presume.
On the way down the slope, the rains are falling on land, temps are not so hot, things are growing. The Northern hemisphere is going from ice to temperate forests, absorbing how much carbon? Well, my envelope calculation says that forest development in North America could take up 400 million tons. How much co2 do we have in the atmosphere now? 600 million tons?
In regards to Lindzen’s discussion of the water vapor feedback: I agree that his statements are misleading, although to be fair if you read the full context of his quote, you can see that he could argue that the “that is shared universally” could refer to the idea he then discusses in answering the question of the warming being fairly modest in the absence of any positive water vapor feedback. What he did though to mislead is to answer the question only in this very limited way. I.e., he took a general question about whether his view on water vapor is shared by other scientists and then answered it in a way that said “Yes” and then going on to discuss only the part of his view that is shared by others without mentioning that all the other stuff he had said about a negative feedback is not. It is the old political trick of not answering the question that you were asked but rather the question that you wish were asked and pretending like it is really answering the question you were asked.
At any rate, I found the last few sentences in his answer to Question 143 to be even more bizarre. How does his claim that the climate system must have negative rather than positive feedbacks jive with the known strong instability of the climate system? In fact, his argument flies in the face of many of the other deniers who use the fact that the climate system is so unstable to somehow imply that the current warming is likely just a natural oscillation. Or is the climate system somehow designed to be highly unstable in response to natural forcings but stable to the forcings that we put on it? [And as an aside, what does Lindzen mean by "but it is politically incorrect these days to speak of the world, or the earth, as in some sense being engineered"? Is he going to come out in favor of intelligent design just as Roy Spencer did?]
The first Lindzen lecture I attended was in the early nineties. Back then he argued that the Ice Ages did not challenge but rather confirm his hypothesis. He emphasised that the planet did not get cold globally during Ice Ages: the tropics remained warm, only higher latitudes cooled. From that he concluded that a negative feedback keeps the tropics at constant temperature. At the time, that was a defensible position: it was early days with proxy data, and these (the famous CLIMAP reconstruction) seemed to show that tropical sea surface temperatures were hardly cooler than today at the height of the last Ice Age. A nagging contradiction (not mentioned by him) was, however, that proxies for tropical land temperatures (e.g. snowlines) did show major cooling.
In the meantime, proxy methodology has advanced and new proxies have emerged (e.g., alkenones and the magnesium/calcium ratio). It is now generally acknowledged that the CLIMAP reconstruction was not correct in the tropics, and that tropical sea temperatures during the last glacial maximum were in fact much colder than today (e.g., SCHAEFER-NETH and PAUL 2003 find 2-4K cooling in the tropical Atlantic). As Gavin wrote, this much glacial cooling is what is expected with mid-range climate sensitivity (SCHNEIDER VON DEIMLING ET AL. in press), and in my view it clearly shows that there is no such negative feedback as postulated by Lindzen, that would stop the tropics from changing. (Besides, the ongoing melting of most tropical mountain glaciers shows that tropical warming is happening as we speak.)
As our knowledge advances through better data, one would expect Lindzen to change his assessment; instead he just does not mention the Ice Age any more in his more recent talks, as the data don’t fit his message any more.
The fact that “climate sceptics” like Lindzen often resort to the accusation that climatologists are “alarmist” to get more funding shows that they’ve run out of factual arguments. But this conspiracy theory also shows very poor logic: climatologists are telling their governments that we know enough to act, not that we are still uncertain and need more research money. If I were cynical, I would welcome the “climate sceptics” – if everything were still as uncertain as they claim, this would be a great reason for me to ask for more funding for basic climate research. Unfortunately, I tend to care a lot more about the future of our children than about my research funding.
It appears to me that Linzden is acting less like a scientist, and more like an advocate promoting a preconceived agenda. Rather than following the evidence where it leads, he is starting with a conclusion, and misrepresenting the facts to fit his preconceived opinions.
The fact that he has many important papers to his credit amplifies the power of his rhetoric, and gives a veneer of credibility to those who insist that the human cause of global warming is far from settled science.
And yet Linzden’s message is founded on an attack against science itself. The danger from Lindzen’s rhetoric lies in the implicit attack on the scientific method. If scientists can’t be believed because they are alarming the public into funding ever more research, than the scientific method is no better than think tank ideology at uncovering the mysteries of the natural world. The greatest damage done to the public mind is that so many people have come to believe this. As a result, many ordinary people have come to think that qualified scientists are nothing but doom and gloom scare mongers, and think tank ideologues are brave defenders of the truth.
This irresponsible idea can only harm to the public good.
Is the latest vostok ice coe the only vostok ice core?
“have a hard time understanding that slight orbital changes in sun angle could cause such a rapid rise in temperature.”
It is not just the angle of the sun,it is it’s distance from the earth and it’s activity (which is infuenced by the planetry positions) which affect the Global temperature.
“Where would all that CO2 come from, the oceans being so cold?”
The oceans over most of the Globe weren’t cold and as they warmed up they released CO2.
“On the way down”(surely this should be up) “the slope, the rains are falling on land, temps are not so hot, things are growing. The Northern hemisphere is going from ice to temperate forests, absorbing how much carbon? Well, my envelope calculation says that forest development in North America could take up 400 million tons. How much co2 do we have in the atmosphere now? 600 million tons?”
The rising concentration of CO2 does not accelerate the rise in temperature and it should, if it as effective as a GHG as you insist”
Re #8 and “On the way down the slope, the rains are falling on land, temps are not so hot, things are growing. The Northern hemisphere is going from ice to temperate forests, absorbing how much carbon? Well, my envelope calculation says that forest development in North America could take up 400 million tons. How much co2 do we have in the atmosphere now? 600 million tons?”
The mass fraction of a gas in the atmosphere is related to the volume fraction by the ratio of molecular weights. The total mass of Earth’s atmosphere is about 5.136×10^18 kg according to recent estimates. CO2 is about 0.00038 of that, times 44.01 AMUs for CO2, divided by 28.92 for normally wet air, from which I get the atmospheric mass of CO2 to be 3.0 x 10^15 kilograms — three quadrillion kilograms or three trillion tonnes.
I have just reviewed the testimony and it mentions: “According to any textbook on dynamic meteorology, one may reasonably conclude that in a warmer world, extratropical storminess and weather variability will actually decrease…”
I have seen a post on RC about evidence (=measurement not model) for increased storm/hurricane intensity (=as result of warming).
Fascinating stuff, really. I get more questions not less.
I stand corrected on the carbon budget absolute values, but not on the relative values. I use this carbon cycle diagram from Dr. Haughton: http://www.whrc.org/carbon/
Now my questions.
Why didn’t the co2 levels peak 10,000 years ago, like they have done before?
Are we trying to say that something changed the glacial cycle so that we are supposed to be stuck at this relatively hot, dry part of the cycle?
Do we really believe that green house carbon did not melt the ice in recent cycles?
Why am I wrong in assuming that as the glacial ice retreats, the first order of business is the direct oxidation of uncovered soils, accelerating carbon release?
Surface carbon on land, plants and soils, is twice the amount in ocean and twice the amount in atmosphere. Given the large scale change on land with advancing and retreating ice, and changes in precipition/temp over the cycle, I would assume land carbon plays a much bigger role than we assume.
Re #15: Note the word “extratropical,” which excludes hurricanes. I think the basic argument is that since the polar regions will warm more under global warming than the tropics, the difference in temperature between the two will decrease and since extratropical storms are driven in part by this temperature difference, they will tend to decrease in intensity.
The pros here are RC can comment more on this…but I believe that this reasoning is believed to be too simplistic. I.e., there are other effects to consider (such as a warming atmosphere holding more water vapor).
For tropical systems, i.e. hurricanes, the situation is different…as the driving force for them is apparently in large part convection which depends on the difference between the temperature at the surface and the temperatures higher up in the atmosphere. There are some basic physical reasons why global warming ought to make the hurricanes that do form more intense although there is no strong evidence either way for an increase or decrease in the number of them that form.
There are two separate effects here. Firstly the storms in the extratropics [50-60N or so] are the mechanism that the atmosphere uses to mix heat towards the poles and away from the tropics [since the Hadley direct circulation can't work away from the equator because the Earth is spinning]. Consequently, in a warmer world, with amplified polar warming, less heat will need to be transported north and so ‘extratropical storminess’ will be less. This is normally an actual decrease in the absolute number of cyclnoes/storms.
However, number two, there is some evidence, from models and observations, that the intensity and strength of cyclones [whether extratropical or tropical ie hurricanes] is correlated with SST. Consequently, in a warmer world, where the sea temperatures are warmer where the cyclones form, there would be more energy available to the cyclone and therefore more ‘storminess’.
So I guess it depends on how exactly you ask the question.
Re my own #18. I should say that this combination of fewer, but more intense storms, is predicted by at least some of the latest climate models, in response to the lower temperature gradient and higher SSTs.
re 16 Matt
“Why am I wrong in assuming that as the glacial ice retreats, the first order of business is the direct oxidation of uncovered soils, accelerating carbon releas”
What mechanism do you propose for this oxidation?
You would get fewer questions if you answered them reasonably
Matt, have you visited a glacier? They push, not cover, soil. When they retreat they leave gravel and rock.
Where did you get the information you’re assuming is true, where did you get the assumptions underlying your questions? Point us to the source of those and we can talk about them.
Although I trust that the writers and moderators for this site are not trying to deceive me, for other viewers this article presents an interesting opportunity: can the moderators encourage Lindzen to give a reply? I imagine that naysayers might dismiss this commentary as reflecting the power of having the ‘last word’ in an argument, however this charge is easily dismissed if Lindzen is properly alerted to this venue.
BTW, this is the first time I’ve contributed to this blog, but I read it regularly and as an outsider to the climate science community I am very grateful for what you do here. I understand this must be a significant distraction from your professions but for open minded individuals who do not always trust what they read in the popular media, this site is an excellent resource.
“Point us to the source of those and we can talk about them.”
Well, I am asking for sources, sorry, I am the student here.
“Till is material that is deposited as glaciers retreat, leaving behind mounds of gravel, small rocks, sand and mud. It is made from the rock and soil ground up beneath the glacier as it moves. Glacial till can form excellent soil for farmland.”http://www.mvs.usace.army.mil/Shelbyville/Glaciers.htm
Like clear cut soil, the first thing that happens is carbon release until new plant life takes off.
Tundra is a better example. When it melts it become a co2 source via microbial oxidation. How much tundra did we have 20,0000 years ago?
The tundra belt would have advance south in front of the polar ice sheet during the last down swing, leaving carbon encapsulated. As the system warmed, all the carbon would successively been released with the retreating ice.
So, the speculation is the ice retreated too fast for plant growth to keep up, and the uncovered carbon never had a chance to fixate, forcing even faster greenhouse build up. Positive feed back.
If the ice retreated fast enough, I would think it worthwhile to consider whether direct burning at the peat soil may even have occured, (natural surface coal does burn) but rapid desertification after the retreating ice surely would have reinfoced carbon release.
Does this website do polls? I think it would be great
to see a poll for the readers and contributers on the
next few years. How much north pole ice cap shrinks.
How much the Artic mean temp goes up. How much
the global mean temp goes up. How much the research budget for
global warming goes up (or down).
Does anybody have any good references how much money is spent
on researching the climate problems? Budget of IPCC? Budget
of think tanks involved? Is there is list anywhere of big
questions or problems that we know are slowing our understanding.
Or maybe a poll on the which 100 million dollar experiment or
sensory system would give the research community the best data.
Thank you for all the smart talk on this site. This site rules.
“Just over 70 years ago, the Mendenhall Glacier rested where you stand. As you look at the glacier, notice the vegetation on the hillside to each side of the lake. As the glacier advanced, it stripped the valley walls of all vegetation much as a giant bulldozer might prepare a yard for landscaping. This trimline, where light and dark green vegetation meet, indicates the highest point reached by glacial ice. The new growth, indicated by the lighter green vegetation, colonized the exposed rock surface as the glacier receded.”
“As the glacier advanced over this area, it rounded and polished any jagged edges of bedrock over which it flowed. After the ice melted away, windborne spores of mosses and lichens â�� the pioneering plants of succession â�� spread rapidly into the area. They first took hold in cracks and issures, modifying their environment until colonizing plants, such as fireweed, willow, alder, and lupine, were able to get a foothold.”
On what’s left behind as an ice cap melts, I’ll go look. I know there’s some info on the Kilimanjaro and South American icecaps at the Ohio State Polar Research page.
I know there’s info somewhere about tundra, but tundra isn’t what’s _under_ ice caps as far as I’m aware. I think most of what’s at the bottom of the ice caps is rock and traces of material, not a large layer of buried soil. At the bottom some melting happens due to pressure and heat that would slowly wash out organic material, I think. That’s just my speculation though.
December 02, 2004
Washington (CNSNews.com) – An MIT meteorologist Wednesday dismissed alarmist fears about human induced global warming as nothing more than ‘religious beliefs.’
“Essentially if whatever you are told is alleged to be supported by ‘all scientists,’ you don’t have to understand [the issue] anymore. You simply go back to treating it as a matter of religious belief,” Lindzen said. His speech was titled, “Climate Alarmism: The Misuse of ‘Science’” and was sponsored by the free market George C. Marshall Institute. Lindzen is a professor at MIT’s Department of Earth, Atmospheric, and Planetary Sciences.
Once a person becomes a believer of global warming, “you never have to defend this belief except to claim that you are supported by all scientists — except for a handful of corrupted heretics,” Lindzen added.
“Meteorologist Likens Fear of Global Warming to ‘Religious Belief’ ”
By Marc Morano
CNSNews.com Senior Staff Writer http://www.cnsnews.com/Culture/archive/200412/CUL20041202a.html
On the other hand,
February 09, 2006
… “A prominent pastor from the Twin Cities was among 86 national evangelical leaders Wednesday who said that global warming is a real and serious problem that needs immediate attention in Congress.
Rev. Leith Anderson, senior pastor of Wooddale Church in Eden Prairie, said the effort is important both to God, who has entrusted the Earth to humans, and to the “poorest of the poor and the marginalized of society,” who are disproportionately affected by climate change.”
“A prominent Twin Cities pastor said global warming needs immediate attention in Congress”
Minneapolis Star Tribune
Tom Meersman and Aaron Blake
Also see: http://www.kare11.com/cs/forums/1359/ShowPost.aspx
For a more complete view of the Evangelical support for immediate action on global warming (strange bedfellows, and all that) check out the Evangelical Climate Initiative. This traditionally conservative christian “denomination”, provides some frank discussion of basic global warming issues in its FAQ
Apparently the movement is supported by many of the Evangelical church’s most high-profile leaders, though no consensus is apparently possible within the church do to polarizing viewpoints on the subject.
Wonder what it’ll suggest is happening. Any one know?
NASA’s supposed to be about finishing up their tropical convection study combining high altitude flights and satellite passes, to get some actual real data on what the atmosphere’s doing around Costa Rica — in the area where the clouds actually drive up to the stratosphere, instead of topping out below it. That would, I suppose, give information relevant to his work.
I don’t know anything more about either the models or the flight research on tropical convection. I hope there were some testable hypotheses on record that the data will inform.
In Lindzen’s defence, I must say that it is often tempting (i.e. human) to overstate the importance of an observation or a point if you are representing a minority view, as his is. The risk is that you get attacked on those points and your other (possibly valid?) points get snowed under. He is not just appearing at conferences/institutes that support the sceptical view (like the Marshall Institute). Lindzen did present a paper at the international conference “Global Warming: Looking Beyond Kyoto” which was held on 21/22 October 2005 and hosted by the “Yale Center for the Study of Globalization”. This was not a conference just for the “believers” or just the “sceptics”. Check their website. I have a natural aversion for accepting a (claimed?) majority opinion and more keen in reading the minority position and I am also allergic to claims that a scientist has an agenda or is sponsored by interest groups, as a way of discrediting him/her. (This applies to “believers” and sceptics” alike)
Many brilliant scientists have resisted a common scientific opinion and dared to come up with a dissenting view. Case in point, the two Australian Nobel prize winners who – against the opinion all other scientists in their field – claimed that ulcers were not caused by stress but by a bacteria. Let that be a lesson to those students that read or contribute to this forum. Let us not forget the prediction of scientists in the 70′s that we were at the point of entering another Ice Age.
[Response: Since this is wrong, you rather destroy your line of arguement... however, its a common myth - William]
And what about the erroneous predictions of the Club of Rome soon thereafter. Unfortunately we cannot easily google for articles written in the early seventies. Most of today’s students had not been born or were just toddlers and have not had the luxury to be sceptical. I am 58 (a geologist) and have seen alarmist’s science before, although the past is not necessarily a reliable guide to the future. On global warming, yes it could indeed be anthropogenic, but I am inclined to support Lomborg and rather spend the billions of dollars on helping fight poverty and disease than trying (in vain) to contain it.
Comment by Chris Schoneveld — 16 Feb 2006 @ 6:02 AM
Could Lindzen have been the basis for (one of) the main character in Crichton’s book “State of Confusion?”
Many thanks to Gavin and all for such an informative web site: your audience is growing everyday.
Re #31 (specifically the stuff about ulcers): Yes, all knowledge is provisional and it is possible for new knowledge to overturn previous knowledge. As #33 points out, this is how things have in fact worked for AGW which encountered plenty of resistance in its ~100 year history before gaining acceptance (see http://www.aip.org/history/climate/ for a history).
However, what you have to remember is that for every “Galileo” shouting in the wilderness, there are probably a thousand Pat’s, Richard’s, and Sallie’s who oppose the current scientific wisdom and turn out to be wrong. If your recipe for having science guide policy is to wait until there is complete unanimity on a subject before doing anything (because those who are disagreeing with the general scientific consensus may be right and the consensus wrong), then you really just might as well propose we simply don’t use science to guide policy decisions because it will amount to the same thing.
As another comment on #31, why does the subject of fighting poverty and disease seem to come up so much when talking about spending money to protect our environment? It is not like these are the only two choices in the world. How about all the money we have wasted on the Iraq War, for example…What if all of that money had been redirected toward weaning us fossil fuels?
Now that I think I’m in the books as retired (from NOAA NWS river forecasting after 30 years), I’d like to bring up an analogy between not predicting climate change and not predicting a flood.
In flood prediction, if your recipe is to have science and scientific observations guide your policy to take action to save a town by waiting until there is complete unanimity before doing anything, then you’ll have a Grand Forks like disaster in the making for your town.
In climate prediction, if your recipe is to have science and scientific observations guide your policy to take action to save the world by waiting until there is complete unanimity before doing anything, then you’ll have a Katrina like disaster in the making for your world.
How about imposing a high gas tax in the US, the proceeds of which would go towards fighting international poverty. That would lower our dependence on oil, a worthwhile goal in any case. As Thomas Friedman and others have pointed out, oil rich nations tend towards corruption and tyranny because rulers have this large source of income they can exploit, which they can use to pacify their populations without giving them much freedom.
I’m pretty sure Senator Inhofe would not support such a proposal. But perhaps he can find some other way to divert funds that might otherwise be spent to avert global warming to alleviating poverty? I won’t hold my breath waiting.
Khabibullo Abdusamatov – chief of the Space Exploration Department of the Central Astronomical Observatory of the Russian Academy of Sciences, the supervisor of the Astrometria project of the Russian part of the International Space Station, Doctor of Physical Sciences.
The scientist particularly said that a global reduction of temperatures would hit planet Earth in the middle of the 21st century because of receding solar radiation. Mr. Abdusamatov told Pravda.Ru that the new Ice Age will start very slowly. According to the scientist, the process will gather pace in 2050-55.
And what about the erroneous predictions of the Club of Rome soon thereafter.
I’ll hazard a guess that this refers to an incorrect but oft-repeated strawdog criticism of the Limits to Growth (LTG) report.
The basic critique runs, “LTG predicted the end of the world in year XXXX, and it didn’t happen.” Usually the year XXXX is chosen, not from one of the World3 runs, but from a table of resource lifetime indices in the chapter on nonrenewable resources, which were not forecasts at all. If you flip through a copy of LTG, you won’t find any runs where industrial output peaks before about 2010, and you will find a number of comments to the effect of “this is a choice, not a forecast” or “more study is needed.” The plots in the book deliberately used a minimally-labeled time axis to highlight the fact that output was meant to illustrate generic behavior modes of a system with rapid growth, long delays, and limits, rather than point predictions of future conditions.
As an example, Bjorn Lomborg writes in The Skeptical Environmentalist (pg. 121 of my edition), “Along with numerous other resources, Limits to Growth showed us that we would have run out of oil before 1992.” What he refers to is a table on pg. 58 of LTG showing static reserve life indices (SRLI) and their dynamic equivalents for a variety of resources. If you read the accompanying text, it’s clear that the table has little to do with forecasting exhaustion. Instead it simply makes the point that the static index (=reserves/current use) is a poor measure of the true lifetime of a resource with exponentially growing use. LTG also recognizes the distinction between reserves and resources, and includes a second column of dynamic indices at arbitrary 5x reserves, to make the point that even large increases in reserves can be overwhelmed quickly by growth. For oil, this yields a dynamic lifetime of 50 years (again, not a forecast and not model-based, but implying exhaustion in 2022, not 1992). Lomborg happily ignores these subtleties and publishes a table of updated SRLIs a few pages later.
I recently skimmed the text for the word “forecast,” unsuccessfully. The closest I could come is (pg. 126): “We can thus say with some confidence that, under the assumption of no major change in the present system, population and industrial growth will certainly stop within the next century, at the latest.” So the jury’s out for seven more decades.
While there are valid things to criticize about LTG (e.g. the Thiessen critique of the nonrenewable resource structure), I get the sense that many critics haven’t actually read the book; they’re just repeating something they heard about it years ago, from someone who didn’t read it either.
Ironically, given that Meadows et al. were regarded as heretics at the time, by the “daring brilliant minority dissent” criteria one could conclude that they were Galileos.
Matt, are you near a public library? Basic school-paper questions are a specialty of the Reference Desk at almost every library — a person worth knowing, wherever you live.
They say research on the Internet is like walking into a huge library and shouting your question into the dark, never knowing who if anyone might answer and how much truth they’re telling you. The Reference Desk is a human face on knowledge and the sources are reliable and checkable.
Lindzen, Lovelock. What is the conscientious layperson to do? How about this: HOPE Lindzen is right, but EXPECT & BE PREPARED for Lovelock’s scenario — or at least for the upper end projections of working climate scientists.
It seems Lindzen is focused very strongly on all that could go right, the lowest end projections, or even below those. Maybe he has a lot of kids and can’t stomach the idea that he (& the other 6 billion of us) have ruined the world for them. Better just to keep one’s head in the sand.
Now, I’ve always fretted that the scientists might even be underestimating the future GW disaster, since they’re just working with what they know, and new knowledge (findings & theories) keep cropping up. The latest one I read is at: http://www.climateark.org/articles/reader.asp?linkid=52528
It says we’ve underestimated the amount of CO2 being pumped out of plant via bacteria under warming conditions, greatly overriding the CO2 intake of plants, and that warming oceans will take in less CO2 than expected. It says the warming by 2100 will be .1 to 1.5 degrees C higher than the accepted range of 1.4 – 5.8.
So best case, that means 1.5 increase. But please let’s not fail to do some planning for the worst case, 7.3. Or, better yet, why don’t we just reduce our GHGs & save money & help the economy. If it takes “alarmists” to get a fire going under people’s backsides to do this, then bring on the alarmists.
Comment by Lynn Vincentnathan — 16 Feb 2006 @ 2:35 PM
Re #39: Call me cynical, but I notice that he picked a date for the cooling that’s sufficiently far off in the future so that even with continued warming he can plan to retire safe in the knowledge that he hasn’t yet been proven wrong by actual temperature measurements.
For what it is worth, my intuition agrees in some ways with Matt’s, if I understand correctly what he is trying to say. My conversations with some of the field’s experts (I won’t embarrass them by naming names) hasn’t entirely dissuaded me from suspecting that that carbon exposed by retreating glaciers and sequestered by advancing glaciers plays a key role in the striking asymmetry of the Quaternary glacial oscillations.
Thank you Tom. I am very familiar with the LTG rebuttal used by those wishing to undermine environmental science. You have summarised the work by Meadows et al and its miss use very succinctly. I work in environmental policy (mainly energy issues and climate change) and have heard this claim so often that I had to go and get (from Amazon) a copy of the original book so that when someone next made this statement I could point out what was actually said in the original book and what has been said in the revisions. Quietly stated facts have had the effect of stopping the conversation in its tracks.
I classify the LTG misquote as one of the Lomborgians key throwaway talking points which they pepper through out their speeches. Some of the others include M&M on the Hockey stick, Lindzen et al on water vapour, Spenser and Christy on Temperature records. A big thanks to Real Climate for helping me with my responses when faced by these claims. Also a big thanks to William for my response to the Ice Age claim of the 1970s.
While I am on this topic of Lomborgian throwaways a big thanks to Tim Lambert, over at ScienceBlogs, for his work on the real policy on the use and non-use of DDT to fight Malaria.
As Pterry says
‘A Lie can run around the world before the truth has got its boots on’ Terry Pratchett (after Mark Twain apparently)
RE current #s 36, 41, 42, 45 (Matt looking for information on a little-studied phenomenon):
If I may, I think Matt’s questions are good, and his search for sources getting three different responses is indicative of the larger difficulty/enterprise at work here.
I think it is instructive that Matt has chosen to ask questions rather than look for quick answers. For those looking for quick, digestable answers then we can thank the authors and this post for pointing out a source and the issues with finding quick answers.
For those looking for the right questions (and the answers that come from those questions, and then questions that come from the answers…usw.), there is no one good source and this is where wisdom and learning come in.
Five minutes of Googling likely isn’t going to give you a good answer, unless you are one that is satisfied with five minutes of effort.
The different responses to Matt’s questions reflect different ways of going about the problem, none of which are right or wrong in themselves, but are context-dependent.
All this preamble to say it is better to get your information from journals in a library than a quick Google…
One more tid bit: Laurie David posted this morning on the maple syrup run in Ohio this year, it didn’t happen. They’re #3 in production, the farmers there are on 100 + year-old farms, it’s never happened in their records. Their trees have already budded.
With regard to minority opinions in science, the example of Galileo tends to come up often. However, what is generally ignored is that Galileo did not face repression from a community of fellow scientists. It was from an orthodoxy of an entirely different type that he met resistance.
In fact, throughout history it has been remarkable how the scientific community has welcomed cataclysmic change with open arms, when it proved to bring a better explanation of the natural world. Centuries of Newtonian time and space, then Einstein comes along and says neither is absolute. No problem! Centuries of a deterministic and continuous world, then Planck, Pauli Dirac and Heisenberg come along and say it must be otherwise. No problem! It is ironic that, in this instance, Einstein was a voice in the wilderness among scientists, arguing for some kind of preservation of the old deterministic orthodoxy.
Dr. Lindzen was on the air today, Michael Krasny’s “Forum” interview program — one of several people participating, although he had to leave to teach a class before listeners were able to call in with questions.
I don’t have a transcript, just memory, but he didn’t speak very long.
He said, if I have it right, that
– there’s been much less warming so far than was predicted,
– he sees no reason to be alarmed about changes observed,
– he believes that most of the people doing research in the field had only gotten involved in it because of large amounts of research money becoming available in the past decade
– only the GISS people, but not the other groups (he listed several) are claiming that 2005 was the warmest year yet.
– temperature for the past ten years or so has “been flat” not increasing (no trend in the past ten years)
– we are at a “high point” where any tenth of a degree can be a new record without being of any significance plus or minus.
We have had frequent contributions to the climate sensitivities debate on this blog, where several fundamental questions remain unanswered. In the case of glacial-interglacial-glacial cycles, the direct forcing by CO2 changes is some 2 W/m2 (see Hansen, slide 12).
But the effect on temperature is the sum of the changes caused by the forcings and their (different) sensitivities. In the case of CO2, in most cycles there is a (huge) overlap between temperature change (induced by Milankovitch cycles) and lagging CO2 changes. With one exception, the onset of the last glaciation. The lag of CO2 (in the Vostok ice core) is such large, that the temperature drop is near complete and ice sheet formation is at maximum, before CO2 levels start to drop (see here for the Eemian and post-Eemian plots).
Ice sheet growth (including -semi- global sea surface/air temperature changes) is measured as delta18oxygen in the gas phase (from N2O) of the ice core, thus any dating error in lags between ice sheet formation, CH4 and CO2 levels is excluded.
As there was no change of aerosols in the period of interest, and CO2 seems to have had little influence on (ice phase derived) temperature, near the whole temperature change at the onset of the last glaciation was caused by insolation shifts to other latitudes and ice sheet/vegetation feedbacks, with some help of CH4 and N2O. CH4 follows more closely temperature changes, while CO2 lags much longer, with in several periods of rapid temperature change no or little (and even opposite) changes.
This points to a low sensitivity of climate to CO2 changes…
[Response: No it doesn't. It points to a) the importance of other forcings in driving glacial-interglacial transitions (specifically the insolation changes), and b) a low sensitivity of CO2 to climate (the other way round from your conclusion). Remember that equilibrium sensitivity is only easily derivable from equilibrium situations, not transients. I have explained why I think that the LGM implies a mid range sensitivity - tell me where I am wrong in your opinion. -gavin]
That the transient sensitivity is lower than equilibrium sensitivity is of course true, but that is also the true for insolation, CH4, ice sheet, vegetation, aerosol,… shifts. The main problem is that in most cases it is impossible to know if there is a difference in sensitivities for different forcings, as in large transitions like glacials-interglacials-glacials, all (feedback) forcing changes are overlapping each other during the transition (that includes the LGM-Holocene transition). But in the exception described, most of the transition occurs in app. 10,000 years, I suppose long enough to reach a large part of the equilibrium for most forcing changes (including deep sea temperature changes), except for CO2, which lags all others. The CO2 decrease of 40 ppmv occured over a period of ~6,000 years, also long enough to reach much of the equilibrium, but the temperature cooled a little further and increased again in the same period (as ice sheets were melting again).
I have not plotted the Milankovitch cycle induced insolation shifts (yet) as that may give some clue of the timing of insolation changes at different latitudes. It is difficult to obtain the relevant data…
Raypierre, there are some less nice examples were an outsider was conflicting with the scientific establishment of that time: Louis Pasteur. It took a lot of years, before the establishment accepted his work…
Re #40 and 47: I also just recently read “Limits of Growth”. Having heard so much more about it from the point-of-view of the Wall Street Journal editorial page than from the environmental side, I expected to see a lot of embarrassing predictions for around the year 2000. So, I was also surprised to see that indeed such predictions are not there. I don’t think one can say that the future has yet proved LoG right at this point but it certainly hasn’t yet proven it wrong either.
One of the few specific quantitative predictions one can find in the book is a prediction of the CO2 levels in the year 2000. When this prediction was made (~1970), CO2 levels were at 320 ppm, or about 40 ppm above the pre-industrial baseline. It was predicted that they would be at 380 ppm, or 100ppm above baseline, in 2000. In fact, that 380ppm is just being reached around now…so, what they predicted would happen in 30 years took about 36 years. That doesn’t seem like too bad a forecast to me, particularly given that this was made before the energy crisis of the mid-late 70s that resulted in substantial efficiency improvements in the use of energy in the U.S. (and presumably much of the industrialized world).
“They laughed at Galileo, they laughed at Pasteur, but they also laughed at Bozo the Clown.” I think that says it all as far as examples of scientists who went against the consensus is concerned. We don’t pay much attention to the many such scientists who were just plain wrong.
Re #51: There’s a free audio archive of this program (and all Forum programs going back several years) at http://www.kqed.org . KQED is the main San Francisco NPR station. They had another GW program in January for which the skeptic of the day was Jim O’Brien (who made an utterly ridiculous claim – unrefuted perhaps because none of the other participants knew enough of the details to say anything – that he had gotten Kerry Emanuel to make a major change in his conclusions regarding increasing hurricane energy).
Re #53: This exchange highlights the difficulty in establishing the extent of some of these forcings going back over millions of years. That said, an important part of the background that often doesn’t get mentioned is that the current cycle of intense glaciation (the Pleistocene) is a rare extreme when contrasted with the last few hundred million years, and that the obvious difference between this period and the much more extensive prior warm times is that CO2 levels now are much lower than they were then; i.e., normal conditions are little or no ice combined with high CO2 levels. One can postulate (as I think Ferdinand does) that the prior warm times are mainly due to their having been much greater insolation, with the increased CO2 levels being primarily a feedback, but as I understand it there is no evidence for the sun being that type of short-term variable star. What is known is that main sequence stars go fairly evenly from dim to bright over the course of their lifetimes. If I recall correctly the sun will increase its brightness by about 75% over its lifetime, the difference in brightness over the last couple hundred million years then being on the order of 1%. For insolation change to be the main forcing over that time, we would need to imagine either that there was extensive short-term variability to overcome the overall brightening, or that some combination of other forcings did the job. Considering all of this, it’s perhaps not impossible to come up with a scenario where insolation change is more likely than CO2 to be the key forcing in the present climate, but to try to do so begins to seem a little strained.
Is there any trace in the ice cores of changes in meteor dust, if that’s visible at all? I know comets don’t leave traces – I mean something changing the level of dust the earth’s atmosphere picks up for millenia but without a lot of chunks large enough to make craters. Maybe a time when the sun was moving through a thick stretch of interstellar dust — which would lower insolation independent of any change in the sun’s behavior and perhaps for a short time.
Do the ice cores resolve anything that’s not attributable to terrestrial sources by composition?
RE: “However, it is conceivable that convective processes might cause more extensive drying due to increased areas of subsidence (the basis of the so-called Iris effect), but this applies mainly to the upper troposphere and in the tropics only. As a general effect, reductions in water vapour as temperature increases in general seem rather unlikely.”
A possibility: Increased energy content in the atmophere results in dynamics which cause the subtropical high pressure centers to grow in size and radial velocity. We go into something resembling a permanent slight La Nina mode (or at least La Nina dominates). That certainly would have effects beyond the tropics. Of course, this assumes that all of the added energy balanced out into actual dynamics, as opposed to simply being lost out into space.
RE: “That said, it’s also clear that glaciations (which have not been present throughout much of history, with ice-free conditions existing as recently as 30M years ago and the current severe glaciations – the Pleistocene – having kicked in just a couple of million years ago) have not been able to exist in the past whenever CO2 has been above a certain level in the atmosphere.”
It was a long time ago. I attended a talk by I believe Arawmick (again, it may have been someone else, but I think it was he) that proposed something a bit different from this. Namely, that the Pleistocene may have started with the closure of the Isthmus of Panama during the previous orogeny. Again, this was long ago and no doubt “discredited” by numerous “climate scientists.” Just thought I’d share my own experience here.
[Response: Not sure what you're trying to imply, but the reason why the Isthmus of Panama idea is no longer subscribed to is simply that it appears to have occurred much earlier that the Pleistocene - more like 4.6 million years ago (Ravelo et al, 2004; Haug et al, 1998), which is too early for the effect you claim. -gavin]
RE: “Not sure what you’re trying to imply, but the reason why the Isthmus of Panama idea is no longer subscribed to is simply that it appears to have occurred much earlier that the Pleistocene – more like 4.6 million years ago (Ravelo et al, 2004; Haug et al, 1998), which is too early for the effect you claim. -gavin]”
I claim no specific effect. That said, 4.6M BP is not all that far in advance of the inception of the Pleistocene, in geological time terms. Let us imagine the orogeny closed the gap and that a number of domino like effects might have then proceded over some stretch of time. How long might it have taken the ocean conveyer to fully settle into its new regime? How long might corresponding changes in atmopheric circulation, after that closure, have taken to fully have their own impacts on the ice balance and on the Arctic Oscillation? Application of a “waveform” (e.g. the transient effects on ocean currents among other impacts) to the Earth’s complex “network” might have resulted in “ringing” and other harmonic effects(to borrow from the language used in field such as seismology and electronics).
[Response: Not likely. The timescales for the atmosphere-ocean system to equilibriate to a change in the basin geometry are on the order of centuries to millennia at most. For resonances on million year timescales you need something tectonic. That isn't to say that the closing of the Isthmus wasn't necessary before the Pleistocene glaciation could occur, but it was not the proximate cause. You might want to read Haug et al (2005, Nature) for some other ideas of what happened at 2.7 Ma. - gavin]
The Iris hypotheses of Lindzen was restricted to the “warm pool” Pacific, where deep convective clouds occur. The amount of cirrus clouds may be reduced if the SST is increasing, leading to faster convection and drying out of the upper troposphere. This would help with the escape of extra IR radiation to space, thus a negative feedback.
The iris hypotheses was quite regional (within the warm pool) and difficult to detect (later work by Lin ea. found an opposite effect: a small warming over the warm pool, but there still is discussion. One of the arguments by Lindzen is where to put the border for cirrus cloud detection).
Later work of Wielicki ea. and Chen ea. discovered that the Walker (between warm and cold parts of the tropics) and Hadley Cell circulation (between tropic regions and the subtropics) increased in strength. The total radiation budget over the whole tropics (30N-30S) changed (~5 W/m2 more IR to space and ~2 W/m2 more insolation, a net loss of ~3 W/m2), less upper troposphere humidity, less clouds and higher vertical air velocities, together with an increase of ~0.085 K/decade of sea air temperatures in the period 1985-1994.
While it is rather difficult to know what is cause and effect in this case (higher SAT leading to faster circulation and less clouds, or less clouds, leading to higher SAT, or both), the net result is an increased loss to space of ~3 W/m2 in only 15 years. That is higher than the total forcing of greenhouse gases since the start of the industrial revolution, for halve of the earth’s surface.
The origin of the changes is suggested to be from natural causes (internal variability, solar cycle(s) – the latter seems plausible, as -low- cloud cover follows closely the solar cycle) by the authors. Thus while Lindzen may be wrong with his Iris hypotheses, due to too small scale of the effect, on the whole tropics, there seems to be a direct connection between SAT and changes in radiation budget, which points to a negative feedback.
Some similar changes in cloud cover happen at higher latitudes too, but the radiation budget by more or less clouds cancels out there. In the Arctic, again cloud trends are reducing the summer warming (more clouds) and increase winter cooling (less clouds).
Stefan’s last sentence suggests that if you care for the future of your children, you MUST agree to (his) views on climate change and AGW. This is quite an unscientific “procÃ¨s d’intention”: I am the father of 4 children, and their future life environment surely matters for me. But this is not reason enough to embrace without restriction every theory or opinion held by Stefan, Gavin et al.
But given you concern for your children, why in the world would you not act given the list of scientific institutions that have all concluded there is a real danger? It is hardly just Gavin and Stephen’s “opinion”.
Every major scientific institute dealing with climate, ocean, atmosphere agrees that the evidence says the climate is warming rapidly and the primary cause is human CO2.
See also this joint statement endorsing the conclusions of the IPCC issued by the Australian Academy of Sciences, Royal Flemish Academy of Belgium for Sciences and the Arts, Brazilian Academy of Sciences, Royal Society of Canada, Caribbean Academy of Sciences, Chinese Academy of Sciences, French Academy of Sciences, German Academy of Natural Scientists Leopoldina, Indian National Science Academy, Indonesian Academy of Sciences, Royal Irish Academy, Accademia Nazionale dei Lincei (Italy), Academy of Sciences Malaysia, Academy Council of the Royal Society of New Zealand, Royal Swedish Academy of Sciences, and Royal Society (UK). http://www.royalsociety.org/displaypagedoc.asp?id=13619
Being a non-specialist, I think it is important to be able to discuss in layman’s terms what we know and don’t know about climate change. What do you say to this comment, which came up with a discussion that I was having with someone on another forum?
“Given the fact that the earth is coming out of an ice age that ended about 12,000 years ago, and that temperatures normally rise after periods of glaciation end, what is the net addition that mankind has added to this overall warming? and can you also account for temperature rises such that which occurred during the medieval optimum that are clearly not driven by human derived green house gasses?”
Is there a source for this . . . and with respect to the rise in temperatures during the medevial period, does my friend bring up a valid point?
Re #65: The joint national academies statement that you linked to is now a few years old and there is a more recent one that states its conclusions in even somewhat stronger terms…and also includes the U.S. National Academy of Sciences as one of the signers: http://nationalacademies.org/onpi/06072005.pdf
Regarding observations of water vapor, an important study came out this summer supporting a positive water vapor feedback that was not metioned in the (excellent) piece by Gavin. Trenberth et al. (2005) find that column-integrated water vapor path has increased globally since 1987, based on observations from satellite-based passive microwave observations. The increases are roughly in line with Clausius-Clapeyron and a constant relative humidity assumption (i.e., increasing SSTs have enhanced oceanic evaporation and led to increases in water vapor).
The rise out of the last glaciation ended ~10,000 years ago and since then it has been relatively stable with a slight cooling until the anthropogenic disturbance we kicked off 100+ years ago. You can refer to this nice graph of various temperature reconstructions of the Holocene (the period since coming out of the last glaciation) http://en.wikipedia.org/wiki/Image:Holocene_Temperature_Variations.png
Actually, I do not need more warnings, I am drowning in warnings! I think most intellectual honest people agree that there is a warming, and that human emissions is one amidst other factors contributing. The difficulty is estimating the importance and danger of this warming, and compare climate change danger to other perils that exist (like terrorism, pandemics etc…). When Hansen tells us that the tipping point will be reached in 7 to 10 years, he leaves not much hope for effective action. It is absolutly impossible to change completely to non fossil fuels in such short a time span; even with the best efforts, this switch-over (that most of us applaude!) will take time. So as a good teacher, will you discourage everybody by giving them impossible targets? And there remains the nagging doubt: what if Hansen is wrong? what if global warming will not accelerate, but slow down…. Is this such an impossible scenario?
I disagree completely with your profession of impossibility. There are literally hundreds of steps, small and large that can be enforced almost immediately with technology currently available. I don’t necessarily disagree that it is not going to happen.
But without going into the details I would just like to say: whether you believe you can, or you believe you can’t, you’re probably right.
Re: 65, please review exactly what Hansen is saying. He talks about the need to stabilize and then start to reduce emissions levels (not atmospheric concentration) of greenhouse gases over the next 10 years. This is consistent with a recent post about whether avoiding 2 degrees of warming is feasible. Hansen is basically giving a reasonable deadline for starting serious efforts to curtail GHG emissions, suggesting no-regrets policies like reducing “black carbon” soot, and pointing out that *when* we act is significant- we can’t wait forever.
Is there any observational method which can determine which currently glaciated areas were ice-free during the last interglacial? Obviously the total ice mass must have been about 6% smaller, but where did it melt from?
so it would make much more sense to define the greenhouse effect as the amount of LW absorbed (~150 W/m2). In which case, doubling of CO2 is initially more like a 4% effect, but as soon as any …
If we’re going to be pedantic the total greenhouse effect is nearer to 155 W/m2 and the forcing for a doubling of carbon dioxide is given by alpha x ln(2) where alpha=5.35 (why it’s as high as that I’m not sure) therefore the forcing for 2xCO2 would be 3.7 W/m2 which is around 2.4% of the total gh effect – so Lindzen’s 2% is closer.
[Response: You are correct. I have amended the post. Thanks. - gavin]
As for any feedback effect, I’d like to see the evidence that this is definitely positive.
[Response: The Soden papers, Trenberth et al, Del Genio etc. -gavin]
RE: Response to #61. So, if I read your reply correctly, you are willing to hang your hat on the assertion that there are no possible harmonics that could have an unexpected impact outside of a time scale of thousands of years? Do I understand your assertion correctly?
[Response:Pretty much. I would state that I am >99% sure that there are no significant power at million year timescales in the coupled ocean/atmosphere/sea ice system. The only source of variability on those timescales is tectonic (including volcanic) and (conceivably) orbital, plus random stuff like asteroid impacts and the like. -gavin]
I’ve wondered about tectonic time scale — has anyone mapped the kind of material being subducted over deep time?
I understand we get new material up that’s spreading from rift zones, being covered with sediment, then all that pushed back down under the next continent to come along.
Do we get layers of deep ocean sediment forming different kinds of material by the time it experiences subduction — so what’s being subducted in one geological period may be much higher in say carbon or calcium or iron or oxygen, because worldwide there was a long episode of a particular climate, long enough that all of its seafloor sediments are characteristic of that climate, then subduction’s chewing on that particular sort of content worldwide for a long while (and so the volcanos pushing up that material would also have a signature)?
Or is the time scale such that the continents ‘average out’ what’s being subducted at any given, er, aeon?
Perhaps an easier question (still one I can’t guess at) — is there any modeling done on this scale? I know the ‘snowball Earth’ idea that we might get ice shutting down primary production worldwide, followed after a long time by melting as volcanic CO2 built up.
RE: #79. This would indeed be a fascinating area of further extensive study. Very old ocean crust would tend to be less mafic than newer crust. Consider crust being subducted by the Aleutian Trench vs. that being subducted by the Cocos Trench. Clearly, the former has a much greater amount of sediment on top of it than the latter. The chance that the former would contain significant variations in composition is greater than the latter. The former would be more rife, at the bulk level, with lighter phases. Etc.
The references I read all say the oceans were 6 m higher during the Eemian interglacial. So ‘about 5 m’ is in agreement. There is no reason to believe any of the largest ice sheets completely melted to produce this rise in sea stand. For example, some of Greenland and some of the West Antarctic ice sheets melting could produce the needed meltwater.
By now there are many ice cores from Greenland. I don’t know that any of these offer evidence of partial melting during the Eemian, but then I find interpreting the ice core data interesting and difficult.
Lastly, there are many fine books on Quaternary geology which may assist one in understnading the complexities. While somewhat older, I profited from studying
“Ice Age Earth: Late Quaternary geology and climate”
which by the way, certainly owes much to Shackleton.
Might be our wonderful RealClimate hosts may care to suggest a more recent volume. If so, I’ll read it as well.
Comment by David B. Benson — 22 Feb 2006 @ 6:24 PM
Following up on #81 –
Web trawling quickly located a gvnmt site regarding Greenland ice cores. The two long cores stop being readable, according to a summary there, at 110 kya. A possible interpreation, my own, not theirs, is that the Greenland ice sheet was losing mass until that date.
There is ice below, but it appears that the drilling stopped about 200 m below the boundary of noninterpretable. This is
consistent with a partial melting of the Greenland ice sheet during the Eemian interglacial. However, other causes may have
been in play.
The only safe one can say, which is what the web site said, was
that there is no interpretable data to be recovered below the depth corresponding to 110 kya.
Comment by David B. Benson — 23 Feb 2006 @ 4:09 PM
You say that more water vapour will increase temperatures (or at least you imply it) – have you considered that more water vapour leads to more clouds, which increases albedo? Can anyone tell me which is more significant? (ie, does the GH effect out-weigh the higher albedo or visa versa)
[Response: The effect of water vapour itself is a postive feedback. The changes in clouds aren't simply tied to water vapour changes (although they are related). However, the net effect of the cloud feedback is made up of both an albedo effect and a greenhouse effect and the net sign is currently unknown. - gavin]