Statistics Needed

JB has asked that we post this interesting article on the Global warming debate.

In the global warming debate, there are essentially two broad camps. One believes that the science is settled, that global warming is serious and man-made, and that urgent action must be taken to mitigate or prevent a future calamity. The other believes that the science is far from settled, that precious little is known about global warming or its likely effects, and that prudence dictates more research and caution before intervening massively in the economy.

The "science is settled" camp, much the larger of the two, includes many eminent scientists with impressive credentials. But just who are the global warming skeptics who question the studies from the great majority of climate scientists and what are their motives?


Statistics needed -- The Deniers Part I
Warming is real -- and has benefits -- The Deniers Part II
The hurricane expert who stood up to UN junk science -- The Deniers Part III
Polar scientists on thin ice -- The Deniers Part IV
The original denier: into the cold -- The Deniers Part V
The sun moves climate change -- The Deniers Part VI
Will the sun cool us? -- The Deniers Part VII
The limits of predictability -- The Deniers Part VIII
Look to Mars for the truth on global warming -- The Deniers Part IX
Limited role for C02 -- the Deniers Part X

Many in the "science is settled" camp claim that the skeptics are untrustworthy -- that they are either cranks or otherwise at the periphery of their profession, or that they are in the pockets of Exxon or other corporate interests. The skeptics are increasingly being called Deniers, a term used by analogy to the Holocaust, to convey the catastrophe that could befall mankind if action is not taken. Increasingly, too, the press is taking up the Denier theme, convincing the public that the global-warming debate is over.

In this, the first of a series, I examine The Deniers, starting with Edward Wegman. Dr. Wegman is a professor at the Center for Computational Statistics at George Mason University, chair of the National Academy of Sciences' Committee on Applied and Theoretical Statistics, and board member of the American Statistical Association. Few statisticians in the world have CVs to rival his (excerpts appear nearby).

Wegman became involved in the global-warming debate after the energy and commerce committee of the U.S. House of Representatives asked him to assess one of the hottest debates in the global-warming controversy: the statistical validity of work by Michael Mann. You may not have heard of Mann or read Mann's study but you have often heard its famous conclusion: that the temperature increases that we have been experiencing are "likely to have been the largest of any century during the past 1,000 years" and that the "1990s was the warmest decade and 1998 the warmest year" of the millennium. You may have also heard of Mann's hockey-stick shaped graph, which showed relatively stable temperatures over most of the last millennium (the hockey stick's long handle), followed by a sharp increase (the hockey stick's blade) this century.

Mann's findings were arguably the single most influential study in swaying the public debate, and in 2001 they became the official view of the International Panel for Climate Change, the UN body that is organizing the worldwide effort to combat global warming. But Mann's work also had its critics, particularly two Canadians, Steve McIntyre and Ross McKitrick, who published peer-reviewed critiques of their own.

Wegman accepted the energy and commerce committee's assignment, and agreed to assess the Mann controversy pro bono. He conducted his third-party review by assembling an expert panel of statisticians, who also agreed to work pro bono. Wegman also consulted outside statisticians, including the Board of the American Statistical Association. At its conclusion, the Wegman review entirely vindicated the Canadian critics and repudiated Mann's work.

"Our committee believes that the assessments that the decade of the 1990s was the hottest decade in a millennium and that 1998 was the hottest year in a millennium cannot be supported," Wegman stated, adding that "The paucity of data in the more remote past makes the hottest-in-a-millennium claims essentially unverifiable." When Wegman corrected Mann's statistical mistakes, the hockey stick disappeared.

Wegman found that Mann made a basic error that "may be easily overlooked by someone not trained in statistical methodology. We note that there is no evidence that Dr. Mann or any of the other authors in paleoclimate studies have had significant interactions with mainstream statisticians." Instead, this small group of climate scientists were working on their own, largely in isolation, and without the academic scrutiny needed to ferret out false assumptions.

read it all.