by Judith Curry
There is much hype and debate surrounding Spencer and Bradwell’s new paper “On the misdiagnosis of surface temperature feedbacks from variations in earth’s radiant energy balance.” So lets sort through all this.
On the misdiagnosis of surface temperature feedbacks from variations in earth’s radiant energy balance
Roy Spencer and William Braswell
Abstract: The sensitivity of the climate system to an imposed radiative imbalance remains the largest source of uncertainty in projections of future anthropogenic climate change. Here we present further evidence that this uncertainty from an observational perspective is largely due to the masking of the radiative feedback signal by internal radiative forcing, probably due to natural cloud variations. That these internal radiative forcings exist and likely corrupt feedback diagnosis is demonstrated with lag regression analysis of satellite and coupled climate model data, interpreted with a simple forcing-feedback model. While the satellite-based metrics for the period 2000–2010 depart substantially in the direction of lower climate sensitivity from those similarly computed from coupled climate models, we find that, with traditional methods, it is not possible to accurately quantify this discrepancy in terms of the feedbacks which determine climate sensitivity. It is concluded that atmospheric feedback diagnosis of the climate system remains an unsolved problem, due primarily to the inability to distinguish between radiative forcing and radiative feedback in satellite radiative budget observations.
Published in Remote Sensing, link to paper [here].
Spencer discusses the paper on his blog.
UAH Press Release
Pielke Sr has posted the UAH press release in its entirety at WUWT. The title of the press release is “Climate models get energy balance wrong, make too hot forecasts of global temperature.” Apart from the title, the press release doesn’t go too much further than the paper. The key quote in the press release IMO is this one:
“The main finding from this research is that there is no solution to the problem of measuring atmospheric feedback, due mostly to our inability to distinguish between radiative forcing and radiative feedback in our observations.”
I agree with this statement. However, if there is no solution to measuring feedback, I would say that SB are concluding too much from their analysis about feedback, sensitivity, and the performance of models.
The article at Forbes.com is entitled “New NASA Data Blow Gaping Hole in Global Warming Alarmism.”. The word “alarmist computer models” is used 8 times in this article, if I have counted correctly. Dudes, it may be appropriate to use the word “alarmist” in some circumstances, but not as an adjective to describe a computer model. The piece concludes with:
When objective NASA satellite data, reported in a peer-reviewed scientific journal, show a “huge discrepancy” between alarmist climate models and real-world facts, climate scientists, the media and our elected officials would be wise to take notice. Whether or not they do so will tell us a great deal about how honest the purveyors of global warming alarmism truly are.
The author of the piece, James Taylor is a lawyer at the Heartland Institute. Dudes, it may be appropriate to use the word “alarmist” in some circumstances, but not as an adjective to describe a computer model. This does not help the Heartland Institute to be taken seriously in the climate debate, even by skeptics.
Climate change debunked? Not so fast
Livescience.com has an article entitled “Climate change debunked? Not so fast.” Some excerpts:
New research suggesting that cloud cover, not carbon dioxide, causes global warming is getting buzz in climate skeptic circles. But mainstream climate scientists dismissed the research as unrealistic and politically motivated.
“He’s taken an incorrect model, he’s tweaked it to match observations, but the conclusions you get from that are not correct,” Andrew Dessler, a professor of atmospheric sciences at Texas A&M University, said of Spencer’s new study.
The study finds a mismatch between the month-to-month variations in temperature and cloud cover in models versus the real world over the past 10 years, said Gavin Schmidt, a NASA Goddard climatologist. “What this mismatch is due to — data processing, errors in the data or real problems in the models — is completely unclear.”
“I cannot believe it got published,” said Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research.
Several researchers expressed frustration that the study was attracting media attention.
“If you want to do a story then write one pointing to the ridiculousness of people jumping onto every random press release as if well-established science gets dismissed on a dime,” Schmidt said. “Climate sensitivity is not constrained by the last two decades of imperfect satellite data, but rather the paleoclimate record.”
“It makes the skeptics feel good, it irritates the mainstream climate science community, but by this point, the debate over climate policy has nothing to do with science,” Dessler said. “It’s essentially a debate over the role of government,” surrounding issues of freedom versus regulation.
Spencer himself is up front about the politics surrounding his work. In July, he wrote on his blog that his job “has helped save our economy from the economic ravages of out-of-control environmental extremism,” and said he viewed his role as protecting “the interests of the taxpayer.” When asked why his work failed to gain mainstream acceptance, Spencer cited funding as a motivation for climate change researchers to find problems with the environment.
Spencer strikes back
Spencer strikes back with this post on WUWT. A few excerpts:
Kevin Trenberth’s response to our paper, rather predictably, was: “I cannot believe it got published” Which when translated from IPCC-speak actually means, “Why didn’t I get the chance to deep-six Spencer’s paper, just like I’ve done with his other papers?”
Finally Gavin Schmidt claims that it’s the paleoclimate record that tells us how sensitive the climate system is, not the current satellite data. Oh, really? Then why have so many papers been published over the years trying to figure out how sensitive today’s climate system is? When scientists appeal to unfalsifiable theories of ancient events which we have virtually no data on, and ignore many years of detailed global satellite observations of today’s climate system, *I* think they are giving science a bad name.
Small cloud study renews climate rancor
Mail.com gets it right with this headline: “Small cloud study renews climate rancor.” Some excerpts:
Several mainstream climate scientists call the study’s conclusions off-base and overstated. Climate change skeptics, most of whom are not scientists, are touting the study, saying it blasts gaping holes in global warming theory and shows that future warming will be less than feared. The study in the journal Remote Sensing questions the accuracy of climate computer models and got attention when a lawyer for the conservative Heartland Institute wrote an opinion piece on it.
The author of the scientific study is Roy Spencer of the University of Alabama Huntsville, a prominent climate skeptic. But even he says some bloggers are overstating what the research found. Spencer’s study is based on satellite data from 2000 to 2010 and is one of a handful of studies he’s done that are part of an ongoing debate among a few scientists.
At least 10 climate scientists reached by The Associated Press found technical or theoretical faults with Spencer’s study or its conclusions. They criticized the short time period he studied and his failure to consider the effects of the ocean and other factors. They also note that the paper appears in a journal that mostly deals with the nuts-and-bolts of satellite data and not interpreting the climate.
“This is a very bad paper and is demonstrably wrong,” said Richard Somerville, a scientist at the Scripps Institution of Oceanography at the University of California San Diego. “It is getting a lot of attention only because of noise in the blogosphere.”
Kerry Emanuel of MIT, one of two scientists who said the study was good, said bloggers and others are misstating what Spencer found. Emanuel said this work was cautious and limited mostly to pointing out problems with forecasting heat feedback. He said what’s being written about Spencer’s study by nonscientists “has no basis in reality.”
Trenberth and Fasullo’s analysis
Trenberth and Fasullo were quick off the block with a post at RealClimate. Some of their main points:
The paper has been published in a journal called Remote sensing which is a fine journal for geographers, but it does not deal with atmospheric and climate science, and it is evident that this paper did not get an adequate peer review. It should not have been published.
The paper’s title “On the Misdiagnosis of Surface Temperature Feedbacks from Variations in Earth’s Radiant Energy Balance” is provocative and should have raised red flags with the editors. The basic material in the paper has very basic shortcomings because no statistical significance of results, error bars or uncertainties are given either in the figures or discussed in the text. Moreover the description of methods of what was done is not sufficient to be able to replicate results. As a first step, some quick checks have been made to see whether results can be replicated and we find some points of contention.
The main part of the TF analysis relates to the comparison of models and observations of the lagged relationship between monthly surface temperature anomalies and net radiative flux anomalies. TF attempt to reproduce S&B’s results, and make a key point that the comparison depends critically on which climate models you select. If you select climate models that do not simulate El Nino’s very well, you will get a poor comparison, whereas you get a good comparison using the best models.
To help interpret the results, Spencer uses a simple model. But the simple model used by Spencer is too simple. We have already rebutted Lindzen’s work on exactly this point. The clouds respond to ENSO, not the other way round [see: Trenberth, K. E., J. T. Fasullo, C. O'Dell, and T. Wong, 2010: Relationships between tropical sea surface temperatures and top-of-atmosphere radiation. Geophys. Res. Lett., 37, L03702, doi:10.1029/2009GL042314.] During ENSO there is a major uptake of heat by the ocean during the La Niña phase and the heat is moved around and stored in the ocean in the tropical western Pacific, setting the stage for the next El Niño, as which point it is redistributed across the tropical Pacific. The ocean cools as the atmosphere responds with characteristic El Niño weather patterns forced from the region that influence weather patterns world wide. Ocean dynamics play a major role in moving heat around, and atmosphere-ocean interaction is a key to the ENSO cycle. None of those processes are included in the Spencer model.
Even so, the Spencer interpretation has no merit. The interannual global temperature variations were not radiatively forced, as claimed for the 2000s, and therefore cannot be used to say anything about climate sensitivity.
I was one of the scientists contacted by the AP, they caught me when I was busy so I did a quick read, here was my response:
The paper itself makes the following point, which is reiterated in the press release: “The main finding from this research is that there is no solution to the problem of measuring atmospheric feedback, due mostly to our inability to distinguish between radiative forcing and radiative feedback in our observations.” This point has been made by others, including myself. Our understanding of feedbacks comes primarily from theory and models; diagnosing feedbacks from observations requires many simplifying assumptions.
The paper is of interest primarily in the context of comparing models with observations in terms of certain metrics, such as the lagged relationship between monthly surface temperature anomalies and net radiative flux anomalies. The models clearly show discrepancies with the observed relationships.
Also, it needs to be understood that given the short period of their data set, Spencer and Braswell are looking only at fast feedback processes associated with clouds (not the longer feedbacks associated with oceans and ice sheets). How to translate all of this into a conclusion that climate models are producing incorrect sensitivity to greenhouse warming is not at all clear.
The paper makes a useful contribution, but in the end they make the same error in interpretation that they accuse others of making. In my opinion it is not correct to infer from their analysis that global temperature variations were largely radiatively forced.
The complexity of the interaction between natural internal variability, surface temperature, clouds and radiative forcing are not adequately sorted out in terms of causal mechanisms to justify such a conclusion, in my opinion.
Challenging climate models with observations is extremely important. I disagree with Gavin Schmidt that paloeclimate data is more robust than the satellite data., but both data sets are essential in this endeavor. So the line of research undertaken by Spencer and Braswell and Lindzen and Choi is an important one, and the issue of better understanding the role of clouds in climate is one of the highest priorities in climate research. But drawing inferences from such studies regarding feedbacks and sensitivity invariably leads to disputes because of the simplicity of the models and assumptions that are used and the fundamental fact that diagnosing feedbacks in the complex climate system can’t really be done. At best you can identify metrics such as the change of radiative flux with surface temperature, and compare observations and models.
TF’s analysis points out some significant flaws in S&B’s paper, and my analysis puts into perspective the relatively limited kinds of conclusions that can be drawn from such an analysis.
So should the paper have been published? I would say yes, although the reviewers and editors should have insisted on more information regarding the climate model simulations that were actually used in their analysis. Was the journal Remote Sensing remiss here? Well no more so than PNAS has been in some recent publications. Remote Sensing is a new open access journal; the only climatologist that I spotted on their editorial board is Toby Carlson. Remote Sensing is a plausible journal to have published this paper, and it seems that Spencer wanted to avoid the possibility of reviews by Dressler and Trenberth. If Roy Spencer didn’t make provocative political statements, this paper would not receive MSM attention and Dessler and Trenberth would probably be less motivated to spend time criticizing his research and wouldn’t be invited by the media to comment on it.
Trying to keep papers from being published isn’t useful (although a good editorial process is extremely useful), and on this particular topic (clouds and climate, comparing models with observations) we need more papers, not fewer. Science proceeds by putting ideas and analyses out there for other scientists to consider and rebut. Add a dose of politics into this, and you exacerbate scientific rivalries into media flame wars. So lets douse the flames and discuss the science.
Moderation note: this is a technical thread and comments will be moderated for relevance. Your general comments should be made on the week in review thread.