Andrew Montford: ‘Consensus’ On Climate Change Just PR Campaign
In recent months it has been stated repeatedly that 97 per cent of scientists agree global warming is real and man-made. These claims are based on a paper published by a team led by John Cook in the journal Environmental Research Letters.
The authors, all associated with controversial global warming activist website Skeptical Science, concluded that 97 per cent of papers expressing a view endorsed the “consensus” position that humans were causing global warming. The paper received an extraordinary reception, being downloaded more than 20,000 times in the first few days after it was published and receiving hundreds of citations from around the internet.
Even Barack Obama’s Twitter feed gave it a mention, claiming it showed “climate change is real, man-made and dangerous”, although the US President had this wrong, since the paper is silent about the possibility of any dangers of climate change.
The amount of media attention the paper received is unsurprising, given it appears to have been written for this express purpose.
Early last year, a security lapse at the Skeptical Science website led to an internal forum for its staff being exposed to public view, and among the contents were several discussions about what became the paper by Cook et al. In one such exchange, Cook explained the paper’s purpose was to establish the existence of a consensus:
“It’s essential that the public understands that there’s a scientific consensus on AGW. So (Skeptical Science activists) Jim Powell, Dana (Nuccitelli) and I have been working on something over the last few months that we hope will have a game-changing impact on the public perception of consensus. Basically, we hope to establish that not only is there a consensus, there is a strengthening consensus.”
These comments strongly suggest the project was not a scientific investigation to determine the extent of agreement on global warming but a public relations exercise. If that is what it was, then it was successful, but its headline-grabbing impact was possible only by drawing a veil over the precise methodology used.
A close examination of what was done shows the paper is built of straw. The authors’ basic approach was to review the abstracts of scientific papers on the subject of climate change, assessing the extent to which they endorsed the global warming “consensus”. However, this first required a definition of what that consensus was about: there is widespread agreement, including among sceptics, that carbon dioxide is a greenhouse gas and that humankind is therefore capable of warming the planet, so the main focus of debate is over how much warming may take place.
The vast majority of scientific papers do not take a position on this question, so the idea of determining the extent of any consensus by a review of the literature in the field was something of a nonsense. The Skeptical Science forum reveals Cook was well aware of this problem and he therefore appears to have decided to adopt a definition of the consensus that was deliberately vague.
The formulation used – “that humans are causing global warming” – could have two meanings. A “deep” consensus reading would take it to mean as all or most of the observed warming was being caused by humans, while a “shallow” one would imply only that some unspecified proportion was attributable to mankind.
By examining the exact protocols used in assessing papers, it is possible to determine which definition applied in practice: when the abstracts were rated, a paper was said to endorse the consensus if it accepted the concept of anthropogenic global warming, implicitly or explicitly, and regardless of whether it quantified the extent of human influence on the planet’s temperature.
A paper was said to reject the consensus only if it minimised the human contribution – for example, by proposing that natural mechanisms dominated – or, more explicitly, if it suggested the human contribution was minimal.
There was therefore an asymmetry in the classifications, with papers accepting the influence of a large or an unspecified level of human influence included in the consensus, and only those actively minimising the human influence recorded as rejecting it. This leads to the unavoidable conclusion the consensus as revealed by Cook et al was indeed the shallow one.
That consensus is therefore virtually meaningless and tells us nothing about the present state of scientific opinion, beyond the trivial observation that almost everybody in the climate debate agrees carbon dioxide is a greenhouse gas and human activities have warmed the planet to some extent.
As Mike Hulme, founder of the Tyndall Centre, Britain’s national climate research institute, put it: “The (Cook et al) article is poorly conceived, poorly designed and poorly executed (and it) obscures the complexities of the climate issue.” The paper is, on close examination, a damp squib.
Andrew Montford is the author of The Hockey Stick Illusion. This article is based on a briefing paper published by the London-based Global Warming Policy Foundation