Why the 97 per cent consensus on climate change still gets challenged

Here are some excerpts from an article I wrote  for the magazine Corporate Knights, that was published on May 14, 2015. Some references and links have been added at the end. This is cross-posted with Skeptical Science.

In 2004, science historian Naomi Oreskes published a short paper in the journal Science concluding there was an overwhelming consensus in the scientific literature that global warming was caused by humans.

After the paper’s release, there was some unexpectedly hostile reaction. This prompted Oreskes and her colleague Erik Conway to go even deeper with their research, leading to the publication of the book Merchants of Doubt. It documents how a small group of scientists with links to industry were able to sow doubt about the scientific consensus and delay effective policy on DDT, tobacco, acid rain and, now, global warming.

Fast forward to two years ago: a team of volunteer researchers (myself included) associated with the website Skeptical Science decide to update and extend Oreskes’ research. Led by University of Queensland researcher John Cook, we analyzed the abstracts of about 12,000 scientific papers extracted from a large database of articles, using the search terms “global warming” and “global climate change.” The articles had been published over a 21-year period, from 1991 to 2011.

As an independent check on our results, we also sent emails to the more than 8,500 scientist authors of these articles. (These were the scientists whose e-mail addresses we were able to track down). We asked them to rate their own papers for endorsement or rejection of man-made global warming.

Both approaches yielded a very similar result: 97 per cent of the scientific literature that expresses an opinion on climate change endorses the expert consensus view that it is man-made. The results were published in May 2013 in the journal Environmental Research Letters.

We were astonished by the positive reception. Mention of the paper was tweeted by U.S. President Barack Obama, Al Gore and Elon Musk, among others. Obama later referenced it in a speech at the University of Queensland, while U.S. Secretary of State John Kerry has referred to the 97 per cent consensus in recent speeches. John Oliver based an episode of his HBO comedy show Last Week Tonight around it, a clip viewed online more than five million times.


The paper has been also been downloaded over 300,000 times – so far – which makes it a blockbuster for a science paper. ….

[Snipped sections concern Richard Tol’s criticisms of Cook et al. and Tol’s history of public disputes along with discussions of the “consensus gap” and scientific consensus as a “gateway belief”.]

…. Climate contrarians everywhere protest there is no scientific consensus. If that were true, they should easily be able to show there is indeed a significant body of work that challenges mainstream science. Yet they haven’t and can’t, because a robust and coherent denial of man-made global warming does not exist.

Our study describes the state of expert opinion, it does not define scientific truth nor does it tell people what to think. Climate scientists today overwhelmingly endorse the consensus view that humans are the cause of most of recent global warming. That’s a fact.

If the goal is to sell doubt and delay action on climate, it’s a fact that has to be denied.

Click here to read the full article at Corporate Knights


References and links

Publications like Corporate Knights limit the number of hyperlinks in their articles. Here are some references and links that bolster the arguments I made.

President Obama’s speech at the University of Queensland.

Graham Readfearn’s article on Richard Tol’s attacks on Cook et al.

Richard Tol’s Energy Policy article on the consensus paper, our reply and his rejoinder (paywalled).

24 Critical Errors in Tol (2014), a document in which we lay out the case against Tol’s critique in more detail than Energy Policy allowed us room for.

Economist Frank Ackerman on the dispute that he and Richard Tol had.

A Statement of Support for Ackerman from many prominent economists.

A Statement from the Stockholm Environment Institute leadership in support of Ackerman (quoted from in my piece).

A Guardian article by Bob Ward on the mistakes that he and others found in one of Richard Tol’s frequently-cited papers.

Richard Tol’s correction in 2014 to his 2009 article, leading, with an attribution statement concerning gremlins.

A further correction in 2015.

Some critical commentary on gremlns by Andrew Gelman.

Yale Climate Change Communication study (2014) that shows the gap between public perception of the scientific consensus on climate and the actual degree of consensus.

The Scientific Consensus on Climate Change as a Gateway Belief: Experimental Evidence(van der Linden et al., 2015).

6 thoughts on “Why the 97 per cent consensus on climate change still gets challenged

    • Yes, I saw that. I believe that the National Post is considering whether or not to allow us to reply to that piece. I will post a link here if they do post a rebuttal.

  1. Good job on your research. I’ve used the 97% stat frequently in arguments with climate denialists 🙂

    I also use the following analogy: if your doctor told you he had detected cancer in your body, you would be wise to go to see another doctor, or even two more doctors, to verify his claims. It is such a life-changing claim that it’s perfectly reasonable for you to get a second or third opinion, before you accept the painful treatment required. But if all three doctors agree you have cancer, it would be unreasonable, and dangerous, to conclude that they’re all wrong, and that you need to do your own research.

    This is essentially what climate denialists are doing. They refuse to believe the experts and become pseudo-experts on climate science to rationalise their denial.

  2. Good luck with the reply. I’ve read the Financial Post for many years, and they rarely print rebuttals. When they do, they have their own response to the rebuttal printed right next to it.

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