Strong Negative Feedback from the Latest CERES Radiation Budget Measurements Over the Global Oceans
By Dr. Roy W. Spencer, Ph. D.
Arguably the single most important scientific issue – and unresolved question – in the global warming debate is climate sensitivity. Will increasing carbon dioxide cause warming that is so small that it can be safely ignored (low climate sensitivity)? Or will it cause a global warming Armageddon (high climate sensitivity)?
The answer depends upon the net radiative feedback: the rate at which the Earth loses extra radiant energy with warming. Climate sensitivity is mostly determined by changes in clouds and water vapor in response to the small, direct warming influence from (for instance) increasing carbon dioxide concentrations.
This can be estimated from global, satellite-based measurements of natural climate variations in (1) Earth’s radiation budget, and (2) tropospheric temperatures.
These estimates are mostly constrained by the availability of the first measurement: the best calibrated radiation budget data comes from the NASA CERES instruments, with data available for 9.5 years from the Terra satellite, and 7 years from the Aqua satellite. Both datasets now extend through September of 2009.
I’ve been slicing and dicing the data different ways, and here I will present 7 years of results for the global (60N to 60S) oceans from NASA’s Aqua satellite. The following plot shows 7 years of monthly variations in the Earth’s net radiation (reflected solar shortwave [SW] plus emitted infrared longwave [LW]) compared to similarly averaged tropospheric temperature from AMSU channel 5.
Simple linear regression yields a net feedback factor of 5.8 Watts per sq. meter per degree C. If this was the feedback operating with global warming, then it would amount to only 0.6 deg. C of human-caused warming by late in this century. (Use of sea surface temperatures instead of tropospheric temperatures yields a value of over 11).
Since we have already experienced 0.6 deg. C in the last 100 years, it would also mean that most of our current global warmth is natural, not anthropogenic.
But, as we show in our new paper (in press) in the Journal of Geophysical Research, these feedbacks can not be estimated through simple linear regression on satellite data, which will almost always result in an underestimate of the net feedback, and thus an overestimate of climate sensitivity.
Without going into the detailed justification, we have found that the most robust method for feedback estimation is to compute the month-to-month slopes (seen as the line segments in the above graph), and sort them from the largest 1-month temperature changes to the smallest (ignoring the distinction between warming and cooling).
The following plot shows, from left to right, the cumulative average line slope from the largest temperature changes to the smaller ones. This average is seen to be close to 10 for the largest month-to-month temperature changes, then settling to a value around 6 after averaging of many months together. (Note that the full period of record is not used: only monthly temperature changes greater than 0.03 deg. C were included. Also, it is mostly coincidence that the two methods give about the same value.)
A net feedback of 6 operating on the warming caused by a doubling of atmospheric CO2 late in this century would correspond to only about 0.5 deg. C of warming. This is well below the 3.0 deg. C best estimate of the IPCC, and even below the lower limit of 1.5 deg. C of warming that the IPCC claims to be 90% certain of.
How Does this Compare to the IPCC Climate Models?
In comparison, we find that none of the 17 IPCC climate models (those that have sufficient data to do the same calculations) exhibit this level of negative feedback when similar statistics are computed from output of either their 20th Century simulations, or their increasing-CO2 simulations. Those model-based values range from around 2 to a little over 4.
These results suggest that the sensitivity of the real climate system is less than that exhibited by ANY of the IPCC climate models. This will end up being a serious problem for global warming predictions. You see, while modelers claim that the models do a reasonably good job of reproducing the average behavior of the climate system, it isn’t the average behavior we are interested in. It is how the average behavior will CHANGE.
And the above results show that not one of the IPCC climate models behaves like the real climate system does when it comes to feedbacks during interannual climate variations…and feedbacks are what determine how serious manmade global warming will be.
Willis Eschenbach, May 11, 2010 at 6:32 pm:
Good story. Was Werner certain about that?
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Smokey says:
May 11, 2010 at 6:55 pm
Willis Eschenbach, May 11, 2010 at 6:32 pm:
Good story. Was Werner certain about that?
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Of course not he was always uncertain in principle.
Willis,
Great joke.
I am not saying that science is infallible…and that what most scientists think will always turn out to be correct. However, I do think that one should endeavor to understand why most scientists have come to the conclusions that they have … and only after very good understanding of how those conclusions are reached is it reasonable to challenge those conclusions. For every Wegener or Marshall and Warren, there are probably thousands of people who think they are like those folks when in fact they are simply wrong.
Joel Shore says: May 11, 2010 at 5:33 pm
“Finally, when paleoclimate folks look at the past climates, they find evidence that indeed the climate seems pretty sensitive to perturbations…and they find that quite rapid changes (e.g., due to the shutdown of the thermohaline circulation) suggestive of tipping points have occurred in the past. So, in fact, it is your view and not the consensus view that seems to be in contradiction to our current understanding of paleoclimate”.
Joel, in relation to the paleoclimate evidence for high climate sensitivity where is your healthy skepticism you claim people should have for Dr Spencer’s science? On paleoclimatic evidence of high climate sensitivity, Dr. Spencer has a healthy skepticism.
The Great Global Warming Blunder, p 68, “Feedbacks are the key”.
“There are actually quite a few ways in which feedbacks have been estimated from observational data, both during the modern instrumental period over the last century or so and from proxy estimates over thousands of years (2). But there is a fundamental problem common to all: our estimates of past temperature change are better than our estimates of the forcings that caused them. And measuring a temperature change without knowing what forced it is the perfect recipe for mistakenly diagnosing positive feedback.
You see, a temperature change can be caused either by a weak forcing that is being amplified by positive feedback, or by a strong forcing that is being reduced by negative feedback”.
And
“I believe our greatest our greatest hope for determining what feedbacks are operating in today’s climate system is by actually measuring today’s climate system. If we cannot figure out from actual measurements on how the climate system operates today, how can we ever hope to rely on past events like ice ages when we have no direct measurements of those events to analyse?”
Who can seriously argue with this logic?
(2) Reto Knutti and Gabriele C. Hegerl, “The Equilibrium Sensitivity of the Earth’s Temperature to Radiation Changes, “Nature Geoscience 1 (2008): 735-1743.
Joel Shore says:
May 12, 2010 at 7:30 am (Edit)
I agree in general, but usually looking at “why most scientists have come to the conclusions they have” is circular. They have come to that conclusion because they have believed in the consensus ideas, so if you don’t question the consensus ideas, you’ll agree with them … how can you break out of that circle?
And yes, for every Wegener or Marshall there are lots of folks who think they are like them. But the current situation is much different from those times. When ulcers were thought to be caused by stress, there were almost no scientists who didn’t believe that. Currently, on the other hand, there are hundreds and hundreds of scientists who question some part of the “consensus”. In fact, there’s not much of a “consensus”, and never was … yes, there’s a consensus that the globe has warmed over the last several hundred years, but when you get to the details, there’s lots of different opinions.
And this is to be expected in a new science such as climate science. The claims of a “consensus” have been political claims, not scientific claims. We understand little about the climate. Nobody saw the recent hiatus in warming coming along … why not? As Trenberth said, we don’t know where the missing heat is … why not?
The answer is that our data is short and scanty and full of lacunae, we haven’t been studying it for very long, the climate is an unimaginably complex system with important phenomena on all spatial scales from microscopic to planetary and extra-terrestrial, and on all spatial scales from nanoseconds to millions of years, and we have no general “theory of climate” like we have in many other scientific fields.
So the idea that there is some kind of “consensus”, the idea that the science is understood well enough to project the climate out for a hundred years, is a non-starter.
Geoff Larson (quoting Roy Spencer) says:
True enough…But, what strong forcing is he proposing occurred during the ice age – interglacial cycles that is being neglected? We know very accurately the changes in orbital parameters that seems to be the trigger of the ice ages. And, we know reasonably well the forcing (in some sense a feedback) due to the albedo changes. And, also the changes in the greenhouse gases and the forcing that this caused.
This sounds more like a rationalization than anything else. Every method of determining the climate sensitivity has advantages and disadvantages. The paleoclimate data has the advantage of being a clean (natural) experiment carried out over long enough timescales and with a large enough change that the equilibrium climate sensitivity can be estimated. However, it has the disadvantage of having occurred in the past so we can’t measure things in real time.
Looking at the current climate system has the advantage of being in real time but the disadvantage of the “experiments” not being as clean, the magnitudes of the change not being large enough, and the timescales not being long enough to accurately gauge the eventual “equilibrium” response and to separate out the signal from the noise.
Looking at models has the advantage of allowing us to do a variety of different experiments on different timescales and turning feedbacks and such on-and-off at will but the disadvantage that the experiments are on a simplified model of the real world rather than the real world itself.
Which is best? The most logical answer is that one should do all of these things. (And, by the way, most scientists who have looked at the current climate have come to different conclusions about what it implies in regards to climate sensitivity than Spencer has.)
Willis,
I am not sure what you expect “consensus” to look like on a scientific theory that people have significant financial, political, and philosophical reasons not to want to believe. I actually think that if you look at other controversial issues (like the origins of our species), you will find similar claims of many scientists believing different things (see, eg., here: http://www.evolutionnews.org/2007/05/scientists_who_support_intelli.html and http://rationalwiki.com/wiki/List_of_scientists_who_support_creationism ). And, like with those issues, most of the arguments that you find supporting the opposing view are just recycled debunked claims (with a few more rational arguments thrown in). Another dead giveaway is the distinct dichotomy between what the professional scientific societies say about the issue and what others claim in regards to where the scientific community stands.
And, yes, the climate system is complicated but that doesn’t mean that we can’t determine anything about it. The human body is even more complicated, at least in the sense that it is further removed from being directly describable by physical laws. (This doesn’t mean the body isn’t ultimately described by physical laws, but just that it is sufficiently complicated that such reductionism usually doesn’t get you very far.)
And, finally, I am not clear how the conclusion that there is a lot of uncertainty should lead to the notion that we should do nothing to reduce our emissions of greenhouse gases into the atmosphere. In fact, what knowledge we do have of the perturbation that we are causing, along with the evidence that the earth’s climate system is subject to some fairly dramatic changes, should push us to err on the size of caution. After all, due to scarcity, fossil fuels will eventually become more expensive and substitutes will need to be found. Wouldn’t it be silly if we just delayed the inevitable and did significant damage to our environment in the process just because we’re not certain that we couldn’t party for another 50 years on fossil fuels before we have to buckle down and face the inevitable?
Joel Shore.
Thanks for responding.
He doesn’t. “Blunder p 69”, “But we also saw that the timing of the Milankovitch cycles relative to the ice ages was no closer to the major temperature changes than what might be expected by chance. Therefore it is reasonable to expect that the ice ages and the interglacial periods of warmth were caused by some as yet undiscovered forcing mechanism”. See his link.
http://ocean.mit.edu/~cwunsch/papersonline/milankovitchqsr2004.pdf
The theory that the ice ages and the interglacials correlate with Milankovitch cycles is speculative. From the summary of Wunsch’s paper above.
“Evidence that Milankovitch forcing ‘‘controls’’ the records, in particular the 100 ka glacial/interglacial, is very thin and somewhat implausible, given that most of the high frequency variability lies elsewhere”.
Certainly there is no consensus on this.
Most scientists have not looked at the problem the way Dr. Spencer is looking at it.
I personally think the “strong feedback is needed for glacial/intergalcial” arguments to be a bit farfetched. Most scientists have not looked at the problem the way Dr. Spencer has, but one that has an analogous view is Tsonis.
It occurs to me that Tsonis 2007 in his work “Heat Capacity” used a similar technique of moving time sliced windows across the entire time domain, and comparing the correlation of the data within each of those times slices with the baseline. This was in reflation to calculating ocean heat. Obviously, some offsets (in time) would show improved correlation over others.
Tsonis showed most variation in global temperature to be the product of aligning or separation of the effects of four major ocean cyclic systems plus a background “secular trend”. That background trend is quite small (I’ll return to this shortly).
Because major variations could be mathematically modeled in this method (and predicted) Tsonis suggested that there was no reason for the “post 1950s temperature rise” to be considered as due to greenhouse gases, and there to be no reason to consider the 1950-1970 cool period to be due to some kind of offsetting effect by aerosol cooling.
That background “secular trend” of Tsonis is quite in line with the small effect of greenhouse gas forcing which Spencer calculates.
References:
Plain english: http://www.worldclimatereport.com/index.php/2007/08/17/climate-change-chaos/
Published article:
https://pantherfile.uwm.edu/kravtsov/www/downloads/GRL-Tsonis.pdf
Joel Shore,
“Most scientists” don’t understand the evidence behind the climate sensitivity issue. Even climate scientists who express an opinion in support of the AGW hypothesis, are unlikely to have reviewed and understood the evidence. Climate science is a multidisciplinary field. Even climate modeling has subspecialties within it, people who focus on cloud parameterizations or the oceans, land, glaciers, snow, etc. For an informed opinion someone would have to have reviewed the model projection, sensitivity and projection literature, the model diagnostic literature and the literature that attempts “model independent” assessments or estimate of climate sensitivity. Of course, even these are sometimes not “model independent”. So who do we have if you look at the scientists working in the area? The largest component is the modelers, these are large, expensive continuing projects and the modeling community also does some of its own diagnostics, but there is diagnostic work also done outside the modeling community enabled by the standardization and open availability of result data. If you exclude the modeling community itself and just look at the people who are informed who have published results supporting some skepticism, I think you will find that using the word “most” is inappropriate. Perhaps a third to a half or more of those informed outside the modeling community can be classified as IPCC confidence and projection skeptics. That is what make the lists such as that recently published by the AAAS such a joke, it is extremely highly unlikely that the biologists and medical professionals on the list have an informed opinion on statement iii:
“(iii) Natural causes always play a role in changing Earth’s climate, but are now being overwhelmed by human-induced changes.”
Let’s not discuss “most scientists, but rather the evidence relevant to whether there is net feedback to CO2 forcing that is positive enough to be a concern. The direct effects of CO2 for the future emissions scenerios are not large enough to justify the expensive initiatives being proposed.