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.
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8 comments:
You're a little vague on solutions. Are you willing to endorse nuclear power?
Jim Bugden
Using the term "denialists" is dishonest. It smacks of John Quiggin like inability to recognize that difference of opinion is acceptable. And it attempts to paint people who have questions about the extent of global warming as unreasonable. The term should be dropped, it adds nothing and makes those who use it appear unsure of their own views to the extent that they must denigrate others.
I strongly agree Civitas - the term adds nothing.
Jim I have posed before that I think we should keep an open mind about nuclear power - search under U3O8. It has expensive capital costs and Australia has lots of coal.
If your view is that we should act on global warming, then it isn't whether nuclear power is expensive relative to coal but whether it is expensive relative to, say, the Kyoto Protocol.
Obviously Jim I think all external costs should be factored in. Without including these coal will win compared to nuclear by a mile. This is well-known.
Harry,
I think you have got this all mixed up.
The Wegman report and the National
Academy of Science report are two
separate reports. The Wegman report
was commissioned by the chair of the
Energy Committee who is apparently a global warming skeptic.
Realclimate.org have a detailed post about it and to quote them:
"Wegman had been tasked solely to evaluate whether the McIntyre and McKitrick (2005) (MM05) criticism of Mann, Bradley and Hughes (1998) (MBH) had statistical merit. That is, was their narrow point on the impacts of centering on the first principal component (PC) correct? He was pointedly not asked whether it made any difference to the final MBH reconstruction and so he did not attempt to evaluate that. Since no one has ever disputed MM05's arithmetic (only their inferences), he along with the everyone else found that, yes, centering conventions make a difference to the first PC. This was acknowledged way back when and so should not come as a surprise."
They then show a number of graphs that show that despite the error, it makes no difference to the actual results. There are also a number of other independent studies using completely different data sets that get exactly the same hockey stick effect.
The National Academy of Sciences report (actually the National Research Council according to Tim Lambert at Deltoid) on the other hand basically said that
1)that they supported Mann et al on the last 400 years
2)and that prior to 1600, the results were plausible.
Go see the following for quotes from the NRC press release
http://scienceblogs.com/deltoid/
2006/06/nas_report_on_hockey_
stick_rel.php
Maybe I'm wrong on this, but the consensus from climate scientists is that AGW is happening.
I agree on the balance of probabilities that AGW is likely to be occurring and say so in the post. I have also been digging into the Wegman report (I may have incorrectly named it- I followed Wood) via John Quiggin's blog and hyperlinks there. I'll read the separate NRC report, thanks.
I don't know of the theory of principal components so have an obstacle. My understanding is that Wegman et al accept the proposition that temperatures have increased substantially over the past 100 years but dispute the inferences about it being the hottest century, the 1990s being the hottest decade etc.
Harry,
I went and read Wood's article and to
be honest it is very one-sided about
the situation. As Tim Lambert points
out why would a journalist trying to
put a balanced view mention the House of Lords report but fail to mention the Stein report which arises from the that very House of Lords report! There are a number of similar problems with his article
To my mind there is only two possible reasons:
1) Incompetence and a complete reliance on secondary sources
2) A deliberate attempt to present a biased view of the issue,
Wood clearly has an agenda, but regardless of which reason, it is hard to take anything that he writes
on climate change seriously.
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