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


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The percentage of climate scientists that claim to agree that humans cause global warming and who are willing to discuss/debate the specific research-based reasons for this agreement is zero. That's zero, nada, zilch.

By Jim McGinn (not verified) on 16 May 2013 #permalink

Real scientists don't hide behind moderation policies.

By Jim McGinn (not verified) on 16 May 2013 #permalink

"The percentage of climate scientists that claim to agree that humans cause global warming and who are willing to discuss/debate the specific research-based reasons for this agreement is zero. That’s zero, nada, zilch."

Huh? Do you have any real point, or evidence-based discussion, or are you simply butt-hurt that the common line that there is no consensus among scientists has been so thoroughly shown to be complete crap?

Tim: Yeah, this iron idea has been around for a while. It would actually draw carbon out of the atmosphere at first. But if it killed the ocean there could be some unintended consequences!

Adding iron is a little like adding CO2. There used to be a lot of both around, both became rare, and during subsequent aeons the earth has evolved to have the amount is has.

sorry, but your so called facts do not fit a political agenda. your argument is invalid.

I am staggered and appalled that any scientific mind, or proponent of statistical accuracy, let alone a group purporting to take a skeptical analysis of data, would dare to use conclusions based on the preclusion of 67% of experts surveyed ie as stated "Removing those papers that did not express an opinion" thereby rendering the rest of the article absolute codswallop, unscientific, biased, agenda based spin.

By Greg Waldron (not verified) on 16 May 2013 #permalink

Greg, take it down a notch. First, you are a climate science denialist so you're not going to like this paper and your bias is going to influence your opinion. Obviously.

This is well done science. If I want to find out how many clusters of prehistoric chipped stone have a certain raw material in them, I might dig a thousand test pits. Let's say I find the material of interest in 10 test pits. Does this mean that there are 10 in 1000 clusters that have this material? No. Because maybe I found 100 test pits with something in them, 900 with nothing in them. I would then interrogate only the part of the sample with flakes. That's a simple example from archaeology that you should be able to understand.

This isn't even close to rocket science. Your bloviation is amusing, though.

Dean, my point was clear. Your inability to dispute my claim also is clear.

By Jim McGinn (not verified) on 16 May 2013 #permalink

Re Greg Waldron, we did not preclude the 67% of experts. On the contrary, by asking scientists to rate their own papers, it gave us an insight into how a full paper handles the consensus versus how an abstract handles the consensus. What we found was most of the climate papers that didn't express an opinion on human-caused global warming in the abstract went on to endorse the consensus in the full paper.

By John Cook (not verified) on 16 May 2013 #permalink

Thanks for the comment, John.

For reasons I mention in this post, it would be astonishing if a larger percentage of abstracts, or even the whole papers, explicitly referred to the overarching paradigm already established on the preponderance of evidence.

Thank you for the clarification,John, but, my whole point was the conclusion that 97% of scientists support the theory.. (when we exclude more than half the original samples). One cannot assume support or dissent based on no opinion offered, the reasons for "no comment" not known. At best the assertion is poorly worded, as is the assertion that I am obviously a climate science denialist. What disturbs me is that apparently manipulated data,is offered as conclusive,which gives opponents opportunities to ridicule the rest of the hypothesis. I have no difficulty understanding the principle of transparent integrity in research.

By Greg Waldron (not verified) on 16 May 2013 #permalink

Jim, it is simply that I'm always stunned to see statements as blatantly ignorant as yours. Thanks for showing your comments were meant to be that way.

Greg, have you read the original paper? Accusing the authors of manipulating the data is very very serious. I just want to make sure that you've read the paper before making that claim.

But anyone who's read even just this blog post will understand that you've utterly missed the point. The thing is you've missed the point so completely that it must be true, were we to give you the benefit of the doubt, that you're missing it pretty much on purpose. That's how I draw the conclusion that you're a denilialist. But maybe you're not. Maybe you just dn't understand sampling. (But if that was the case why would you not simply address my analogy meant to help you understand? Did you read that comment?)

Interesting that you bring up the Weather Channel, since it's founder considers global warming to be " the greatest scam in history".

So...100% of the Weather Channel founders agree AGW is a scam. Since 100% is greater than 97% and clearly "science" is determined by a democratic process of federal bribes, you lose the argument?

Ron, Coleman is not a scientist and has never done research in climate science. Did you not know that, omit that fact willingly, or fail to mention it because you don't understand why his uninformed opinion doesn't matter?

I agree! We need to utilize alternative energy as a mainstream source to offset the pollution and shortage of our natural resources. Thank you for sharing.

By Lauren@GreenGl… (not verified) on 17 May 2013 #permalink

Well, that link is five years out of date, and the source it links to is gone, so I'm not sure how important it is.

The thing is, TWC has been a friend to climate change activists and those interested in the issue. They seem to be doing an increasing amount of education about the topic. Mr Coleman's opinions are his own, not company policy, apparently. Also, as I noted, I'm not sure we can pin a statement he made five years ago on him. Lots of people have changed their minds over time as more information has come along.

Do you have anything more recent on his opinion? It probably would not matter too much.... the TWC is doing what it is doing, and that is what counts.

Coleman is no longer associated with the weather channel. I would also note that his only education seems to be in journalism. He was not a weather man, just a weather copy reader.

Greg - you have in your post "11,9934" abstracts surveyed - it that a misplaced comma or an superfluous digit on the end?

By Doug Alder (not verified) on 17 May 2013 #permalink

Well, the first poster was Jim McGinn;
His argument was mighty thin...

So drill ye tarriers drill.

Jim: The percentage of climate-change deniers who are willing to read the relevant research papers, or even look at the evidence reported on blogs like RealClimate or SkepticalScience, may not be zero. But it is very small.

Once again, if there were any actual evidence that AGW is not real, whoever presented it would be a hero. So what are you waiting for?

This, after all, is how science is done — not by staged debates where the winner is whoever is more glib.

By Chris Winter (not verified) on 19 May 2013 #permalink