Alan Wood in The Australian today firmly denies that a consensus on global warming has developed. He draws on an ABARE report emphasising the role of uncertainty in evaluating the issues. He also attacks the UN’s Intergovernmental Panel on Climate Change (IPCC) - the main source of the current consensus wisdom. The argument is the familiar one that the IPCC relies on the ‘hockey stick’ model of climate change - that after 900 years global warming during the 20th century takes off in a sharp upward surge like the end of a hockey stick. The 20th century was the warmest for the past 1,000 years, the 1990s were the warmest decade, 1998 was the warmest year and so on.
Michael Mann who developed this model has had his work criticised bySteve McIntyre and Ross McKitrick among others. These critiques have in turn been scrutinised both from the viewpoint of statistical logic and from a science/cultural viewpoint. Most recently the US National Academy of Sciences led by US statistician Edward Wegman have got into the act and supported the McIntyre-McKitrick critique of Mann.
‘Overall, our committee believes that Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis’.The Wall Street Journal editorialise on the basis of Wegman et al that current temperatures are within the range of normal variation given history. This poses problems for the IPCC which uses the hockey stick has a foundation for its views on climate change and uses the hockey stick as a logo. The hockey stick theory might be a lie!
An inconclusive exchange of insults on the Wegman et al document is at Deltoid. Generally the approach there seems to be – accept the evidence supporting the hockey stick and display impatience with respect to evidence that doesn’t. As debates go there is more heat than light.
What to make of this? Wegman et al comment in their report that the case for global warming isn’t suited for discussion on Web logs and maybe that is right. It is discouraging that such an important debate has taken such an inconclusive turn. But I don't change my pro-action views. On the balance of probabilities I think global action to deal with greenhouse gas emissions is sound policy. I'll have to live with the fact that I might be wrong.