Tag Archives: AGW Consensus

The Consensus on Climate Change

Sadly, a large percentage of Americans are under the impression that climate scientists do not agree on the reality of anthropogenic global warming (AGW). A lot of people are simply wrong about this. They think that there is a great deal of controversy among the scientists who study the Earth’s climate. But there isn’t. One way we know this is from a study done by John Cook, Dana Nuccitelli, Sarah A Green, Mark Richardson, Bärbel Winkler, Rob Painting, Robert Way, Peter Jacobs, and Andrew Skuce, called “Quantifying the consensus on anthropogenic global warming in the scientific literature

In that study, the authors analyzed “the evolution of the scientific consensus on anthropogenic global warming (AGW) in the peer-reviewed scientific literature, examining 11,944 climate abstracts from 1991–2011 matching the topics ‘global climate change’ or ‘global warming’.” They learned that “66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming.” Among the papers that expressed a scientific position on the topic, “97.1% endorsed the consensus position that humans are causing global warming.”

The study was actually a bit conservative, as in order to be counted as part of that ~3% not supporting the consensus position on AGW a paper did not really have to be fully against the idea. Also, since the study was done, the consensus has increased. I asked study author Dana Nuccitelli about more recent changes in consensus, and he told me, “The consensus is growing over time, and reached 98% in 2011 (the last year included in our survey). So by now the minimizers/deniers are probably in the 1-2% range in the peer-reviewed literature (contrary to the ‘crumbling consensus’ claims).”

The other day I was giving talks at a local high school, and between classes, found myself chatting with a science teacher who had just completed a module on climate change and AGW. She asked me, “Isn’t there now research that shows that the consensus isn’t really as high as previously thought? Or is that bogus? Sounds bogus to me.”

Yes. Bogus.

I’m not sure what research the teacher was referring to (it was just something she had heard about) but there is a paper just published in “Energy Policy” by economist Richard Tol, who as far as I can tell has been a naysayer of climate science for some time now. Tol’s abstract says:

A claim has been that 97% of the scientific literature endorses anthropogenic climate change… This claim, frequently repeated in debates about climate policy, does not stand. A trend in composition is mistaken for a trend in endorsement. Reported results are inconsistent and biased. The sample is not representative and contains many irrelevant papers. Overall, data quality is low. Cook’s validation test shows that the data are invalid. Data disclosure is incomplete so that key results cannot be reproduced or tested.

Nuccitelli has responded to Tol’s paper, in a post at Skeptical Science called “Richard Tol accidentally confirms the 97% global warming consensus.”

Concern Tol-ing

Tol is practicing a special kind of science denialism here, sometimes called “seeding doubt” or as I prefer it, “casting seeds of doubt on infertile ground.” In other contexts this is called “concern trolling” or the “You’re not helping” gambit. The first of two paragraphs of the Conclusion section of Tol’s paper reads (emphasis added),

The conclusions of Cook et al. are thus unfounded. There is no doubt in my mind that the literature on climate change overwhelmingly supports the hypothesis that climate change is caused by humans. I have very little reason to doubt that the consensus is indeed correct. Cook et al., however, failed to demonstrate this. Instead, they gave further cause to those who believe that climate researchers are secretive (as data were held back) and incompetent (as the analysis is flawed).

Let’s get straight that Cook et al is not flawed, despite Tol’s complaints.

Tol’s main complaint is in the coding of the abstracts. He claims that it is imperfect. Well, duh. This is, essentially, social science research, and coding of text is imperfect. Tol makes the claim that the imperfections, if corrected, might bring the consensus down to a dismal 91%. I’m pretty sure he’s wrong about that, but if he is right, we are not impressed.

Tol’s key point is that the papers that are coded as not making a claim include some that do. He then incorrectly calculates how many of of those, if coded “correctly” there would be, and using this, downgrades the consensus to 91%

Nuccitelli explains in detail, in his post, how Tol’s re-analysis is badly done (see the amazing graphic at the top of this post) (go read it) and notes:

In reality, as our response to Tol’s critique (accepted by Energy Policy but not yet published) shows, there simply aren’t very many peer-reviewed papers that minimize or reject human-caused global warming. Most of the papers that were reconciled ‘towards stronger rejection’ went from explicit to implicit endorsement, or from implicit endorsement to no position. For abstracts initially rated as ‘no position,’ 98% of the changes were to endorsement categories; only 2% were changed to rejections.

Nuccitelli also notes that a separate study indicates that Tol’s method is flawed in the sense that no matter what data are used, the consensus will be decreased as an artifact of the methodology. Nuccitelli notes “…by making this mistake, Tol effectively conjured approximately 300 papers rejecting or minimizing human-caused global warming out of thin air, with no evidence that those papers exist in reality. As a result, his consensus estimate falls apart under cursory examination.”

Amazingly, when the Consensus research team fixed Tol’s methodology but applied the same question about coding papers in the no-position category, and re-calculated the percent consensus, it went up by 0.1%. Also, as Nuccitelli points out the Cook et al paper is not alone, and there have been a number of other studies that show essentially the same level of consensus among papers and/or scientists.

So, the consensus is real and isn’t going away. As is also the case with Anthropogenic Global Warming.

Global Warming Consensus: We can haz it!

An important study has just been published1 examining the level of consensus among scientists about climate change.

ResearchBlogging.orgThe issue at hand is this: What is the level of agreement in the scientific community about the reality of climate change and about the human role in climate change? The new paper, Quantifying the consensus on anthropogenic global warming in the scientific literature, address this question and the answer is very clear. The number of climate scientists who question the reality of global warming or the human role in global warming is vanishingly small.

This is not the first study to look at this question, but it is the most thorough effort. This should, however, be the last paper to report this kind of research because, really, we’re there; climate scientists are in very strong agreement about this issue and with this landmark study further demonstration of this fact is superfluous. (John Keegan discusses the merits of this paper relative to other similar efforts and closely examines issues such as sample size and bias here.)

How do we know there a consensus among scientists about human-caused climate change?

The research team, John Cook, Dana Nuccitelli, Sarah Green, Mark Richardson, Barbel Winkler, Rob Painting, Robert Way, Peter Jacobs and Andrew Skuce, examined 11,944 abstracts published in peer reviewed scientific journals from 1991–2011 that covered the topics “Global Climate Change” or “Global Warming.” They coded the abstracts to signify the apparent position on Anthropogenic Global Warming (AGW) and found that 66.4% expressed no position, 32.4% indicated acceptance of AGW, 0.7% rejected AGW and 0.3% expressed uncertainty as to the cause of warming.

Removing those papers that did not express an opinion, 97.1% “endorsed the consensus position that humans are causing global warming.”

The paper also looks at change over time in scientific consensus. The bottom line is that there isn’t much; consensus is not especially new. But there is a small trend, discussed by lead author John Cook in the video I provide below. Also, a look at the “reject AGW” papers shows that there are some patterns. Most are looking at large scale (known) change or cosmic sources of climate change, and they tend to be dated to the earlier part of the time range. Rabbet Run lists them here.

Consensus is often implied and not stated in peer reviewed papers

The researchers then invited the authors to rate the papers they had published. When this was done, the number of papers indicating no position on AGW dropped precipitously to 35.5%. In this rating system, 97.2% of papers endorse the consensus on AGW.

This is important for a couple of reasons. For one, it is an indication that the original coding was conservative, and did not involve assumptions about what the authors may have been thinking. It also shows something about how the scientific process works. If you look at any major scientific concept in the literature, you may find very little explicit endorsement of the overarching theoretical construct or model (like “Natural Selection” or “Germ Theory”) if that concept is fully established. Early writings on a particular major concept often refer to the concept itself and may cite early authors. For example one might see something like “Darwin’s concept of Natural Selection is being increasingly applied to understand the physical features of butterflies” with a reference to The Origin of Species. But after a while scientists stop mentioning the no-longer-novel overarching consensus and stop citing the seminal works. Climate science has moved into this state with respect to the human-caused warming of the earth because of the preponderance of evidence of AGW.

The Climate Change Consensus Gap

Depending on which poll you look at, and when the poll was taken, somewhat more than half of Americans either reject global warming as even being real, reject the human role, or simply don’t know about it. Given the scientific consensus, this is a little like saying that over half of Americans don’t accept Evolution as a valid set of theories and observations, despite the preponderance of evidence for that! (Hey, wait a minute…)


The point is, the gap between scientific consensus and public opinion is real, and very important. The consensus gap causes bad things to happen. For instance, it is quite reasonable for a government agency to fund or support public service announcements on drunk driving. There is a consensus that drunk driving causes deaths, injuries, and accidents. There is not a consensus gap in that area. But global warming also causes misery and mayhem. Shouldn’t there be public service announcements on saving energy and using alternative sources? The consensus gap means that there can’t be.

This of course has a direct effect on public policy, as noted by Naomi Oreskes writing for Science Magazine:

Policy-makers and the media, particularly in the United States, frequently assert that climate science is highly uncertain. Some have used this as an argument against adopting strong measures to reduce greenhouse gas emissions. For example, while discussing a major U.S. Environmental Protection Agency report on the risks of climate change, then-EPA administrator Christine Whitman argued, “As [the report] went through review, there was less consensus on the science and conclusions on climate change”. Some corporations whose revenues might be adversely affected by controls on carbon dioxide emissions have also alleged major uncertainties in the science (2). Such statements suggest that there might be substantive disagreement in the scientific community about the reality of anthropogenic climate change. This is not the case.

Leadership is when those with influence head directly for the truth, talk about the right thing to do, and help other people to do the right thing. Main Stream Media does not have that … that leadership thing. Main Stream Media does not look at the scientific consensus and then make judgements about what stories to cover and how to cover them on that basis. Rather, Main Stream Media looks at the range of public opinion and treats that as consensus (or lack of) and acts accordingly. Which, in turn, reinforces or even sometimes widens the gap.

This also causes problems in the liminal area of media commentary. Opinion editorials in major outlets like the Wall Street Journal often exploit the Consensus Gap, manufacturing uncertainty or attracting readers from among the misinformed part of the public, and again, reinforcing or even widening the gap and enhancing the level of public misunderstanding or just plain old ignorance. With respect to global warming, it is time for that to stop. As noted by Brendan DeMelle:

It does not get any clearer than this. It should finally put to rest the claims of climate deniers that there is a scientific debate about global warming. Of course, this bunch isn’t known for being reasonable or susceptible to facts. But maybe the mainstream media outlets that have given deniers a megaphone will finally stop.

Global Warming, Big Foot and the Loch Ness Monster

Editorials in Main Stream Media that exploit the consensus gap could be compared to editorials at the New York Times or in the Scientific American or your local newspaper that demand more attention be given to the plight of Big Foot or the Loch Ness Monster. The degree of scientific consensus that those creatures do not exist is about the same as the degree of consensus that AGW is real, though the public “belief” in crypto-critters is less than the public “belief” that AGW is not real. Why? Because Main Stream Media has not taken Big Foot or the Loch Ness Monster seriously in quite some time.

Ten years from now it will be interesting to look back and see how Main Stream Media’s editorial writers who today are sticking with “the jury is still out” on AGW managed their reputations as they looked more and more like they belonged at the National Enquirer rather than a respected news outlet.

John Cook, the study’s lead author, has also blogged about it here and also has a video summarizing the paper, which he discusses some of the earlier research as well:

Dana Nuccitelli, another co-author, blogged about the research here and here.

This work was also covered by The Weather Channel.

1The embargo ended overnight last night, even though several climate science denialists failed to respect the embargo, thus, seemingly on purpose, violating a pretty standard ethical rule in academia.

The Consensus Project has a web site HERE and the twitter tag is #TCP

This is the paper:
Cook, J., Nuccitelli, D., Green, S., Richardson, M., Winkler, B., Painting, R., Way, R., Jacobs, P., & Skuce, A. (2013). Quantifying the consensus on anthropogenic global warming in the scientific literature Environmental Research Letters, 8 (2) DOI: 10.1088/1748–9326/8/2/024024