Climate change: the real deal

21 May, 2013 02:00 AM

ON the weekend, the most comprehensive analysis of peer-reviewed climate research to date was published in the journal Environmental Research Letters.

Our analysis found that among papers expressing a position on human-caused global warming, over 97 per cent endorsed the consensus position that humans are causing global warming. Overwhelming agreement among scientists had already formed in the early 1990s. And the consensus is getting stronger.

In a previous Conversation article, I argued that climate denial is essentially consensus denial. For over two decades, attacking the scientific consensus has been a central part of the movement to prevent meaningful climate action.

As early as 1991, Western Fuels Association spent $510,000 on a campaign to “reposition global warming as theory (not fact)”. Their strategy was to construct the impression of active scientific debate using dissenting scientists as spokesmen. This approach was concisely articulated in a memo to Republicans by political strategist Frank Luntz, leaked in 2002:

Using Skeptical Science’s taxonomy of climate myths, a recent analysis tracked climate misinformation published in opinion editorials from 2007 to 2010 by syndicated conservative columnists. The most popular myth was “there is no consensus”. More recently, a variation of the “no consensus” myth has emerged – the notion that the consensus is “on the verge of collapse”.

Our analysis examined the status of the scientific consensus over 21 years of published climate research, from 1991 to 2011. We searched for any papers matching the search “global warming” or “global climate change” in the Web of Science, a database of scientific peer-reviewed research. We rated the level of endorsement of human-caused global warming in each abstract, a short summary at the start of each paper.

In 2007, Naomi Oreskes predicted that as a consensus forms, fewer papers should explicitly endorse the consensus position. For example, you don’t expect to see geography research papers endorsing the fact that the earth is round. Our analysis confirmed this prediction, finding most abstracts didn’t state a position on whether humans were causing global warming.

However, we did identify over 4000 abstracts that did state a position on human-caused global warming. Among those 4000 abstracts, 97.1pc endorsed the consensus. There was overwhelming agreement on human-caused global warming in every year since 1991.

To independently check our results, we also invited the thousands of scientists who authored the climate papers to rate the level of endorsement of their own papers. We received 1200 responses with over 2000 papers receiving a “self-rating”. Interestingly, most of the abstracts that we rated as “No Position” turned out to endorse the consensus in the full paper, according to the papers’ authors. Among all the papers that were self-rated as expressing a position on human-caused global warming, 97.2pc endorsed the consensus.

ABOVE: The level of consensus among climate papers stating a position on human-caused global warming (Cook et al 2013)

Our results are strikingly consistent with other measurements of consensus. The seminal work on consensus was conducted by Naomi Oreskes, who in 2004 analysed 928 climate papers. She found zero papers rejecting the consensus. We analysed the same papers as Oreskes and similarly found zero rejections in the papers matching her search parameters.

Two more recent studies have sought to measure the level of consensus in the scientific community. A survey of Earth scientists found that among actively publishing climate scientists, 97pc agreed that humans were significantly changing global temperature. A compilation of scientists making public statements on climate change found that for the scientists who had published peer-reviewed climate research, there was 97pc agreement.

While a number of studies have independently established overwhelming agreement among climate scientists, two decades of sustained attack on the consensus has been effective. There is a gaping chasm between the public perception and the actual 97pc consensus. When a US representative sample was asked how many climate scientists agree that humans are causing global warming, the average answer was around 50pc.

ABOVE: Perception of consensus (survey of US representative sample by John Cook) versus the 97% consensus (Doran et al 2009, Anderegg et al 2010, Cook et al 2013).

Why is climate denial synonymous with consensus denial? Social scientists are just starting to figure out what climate deniers have understood for decades. A 2011 study found that when people correctly understand that climate scientists agree, they are more likely to support policy to mitigate climate change. This is why a political operative hired by fossil fuel interests to undermine climate policy focused on attacking the consensus, arguing “If we win the science argument, it’s game, set, and match.”

This underscores the importance of correcting the mis-perception that scientists are still debating whether humans are causing global warming. An important step towards stronger public support for meaningful climate action is closing the consensus gap.

The results of the paper Quantifying the Consensus on Anthropogenic Global Warming in the Scientific Literature are summarised in a simple, user-friendly manner at

John Cook does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

The Conversation
  • This article was originally published at The Conversation. Read the original article.

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    21/05/2013 2:50:50 AM

    What a storm on an A4 form. Warmists can't explain the no rise in temperature, so they go back to the models they own and control and to the journals they have placed their activists on. Activists refused to print non human warming papers, so they are agreeing with themselves. According to them, Nature is wrong because it does not agree with their useless models.
    Dirty Redneck
    21/05/2013 8:30:26 AM

    These warmist people must be getting desperate. When the whole man made warming scam is collapsing around them, ramp the warming/consensus BS up even harder. The games up you idiots, continually repeating the same scaremongering AGW scaremongering crap has failed.
    21/05/2013 8:31:06 AM

    Wow. I've never seen a scientific community push their agenda with such hostility as this. If the science was sound, they would be happy to put their theories through the scientific method and let their research speak for itself. Instead we're threatened to agree with it or die. You don't see this agressive behaviour in any other scientific field. Why are the scientists so interested in forcing us to believe? Why are they so quick to shoot down any evidence that remotely contradicts their own? You receive more credibility if you allow critical review of your work.
    21/05/2013 8:47:45 AM

    Spot on the money Mathew. And there can only be a few logical answers to that question of why we are being forced to believe their lies. Money, power and control are the obvious conclusions.
    the kid
    21/05/2013 8:52:46 AM

    Wow yourself! Deniers listen to marketing posing as 'fact' paid for by the lobbyists. You don't seem to get it, you're falling for the same trick smokers fell for when the same marketing companies (paid by tobacco companies) told us that smoking isn't bad for your health.
    Bushie Bill
    21/05/2013 10:36:02 AM

    Ah kid, a spark of intelligence in an ocean of ignorance, (perceived) self-interest and brain-blowing lack of objectivity, study and independent open-mindedness. Absolutely breathtaking, but totally expected, and in a way, very comforting, because it fully justifies intellectually and educationally sophisticated polite society's opinion that RARA is populated by rednecks who are barely able to read and write. It makes it easier for whatever party is in power to keep a jackboot on their necks.
    Bill Pounder
    21/05/2013 11:22:30 AM

    Somehow or other JC missed these 1100 peer reviewed papers concluding otherwise. "I do confess a degree of fascination with Poptech's list..." 2009/10/peer-reviewed-papers-supp orting.html "The exception proves that the rule is wrong. That is the principle of science. If there is an exception to any rule and if it can be proved by observation, that rule is wrong." Richard Feynman
    Jezza yass
    21/05/2013 11:32:53 AM

    I have never heard of any scientists forcing any one to beleive in any thing. If you don't believe in climate change that's fine, I think it's on so I try to manage my place accordingly. Why are you folks getting so wound up over it?
    Dirty Redneck
    21/05/2013 11:43:22 AM

    And as usual Bushie all you have wrote is a lot of ignorant feel-good crap from someone who does not have anything intelligent to say at all because he knows his whole argument is baseless crap.
    john from tamworth
    21/05/2013 11:55:15 AM

    John Cook is a blogger and who knows how he constructed this fallacy and who cares. But there is no hiding from the fact that there has been no global warming for 16 years. There is also no hiding from the fact that all of the 24 IPCC global circulation models have been consistently wrong and have forecast temperature increases that simply have not occured. The AGW hypotheses has failed the test of science cannot predict the natural world, so it should be dropped before another $100 billion is wasted.
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