Questions haunt global warming ‘hockey stick’

July 11, 2005
In quick succession, the science of global warming has pushed its way into politics, and politics has pushed back.

In quick succession, the science of global warming has pushed its way into politics, and politics has pushed back.

On June 7, the national science academies of the G8 nations plus Brazil, China, and India issued a statement urging governments to act in response to climate change. “The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action,” the statement said, calling for “cost-effective steps” to reduce net global emissions of greenhouse gases. The statement obviously was timed to influence events at a G8 summit this month. Thus have the national academies become political institutions.

So politics responds. On June 23, US Reps. Joe Barton (R-Tex.), chairman of the House Committee on Energy and Commerce, and Ed Whitfield (R-Ky.), chairman of the Subcommittee on Oversight and Investigations, sent pointed inquiries to scientists associated with a politically crucial element of climate change research-the notorious hockey-stick record of abnormality in calculated global temperature.

On a plot of that record, temperature change is relatively flat from AD 1000 until a jump in the last century, when greenhouse gases have been building up in the atmosphere.

The hockey-stick curve seems to discredit temperature-proxy records indicating a period warmer than the present during 1000-1400, called the Medieval Warm Period, followed by a relatively cool period during 1400-1900, the Little Ice Age.

By flattening natural cycles, the hockey-stick plot makes the last century’s gain in measured temperature look unprecedented and strongly correlated to the greenhouse-gas increase. Scientists of the G8 national academies obviously put great store in it.

But the hockey stick has come under attack. Analysts see flaws in the underlying mathematics. With the alleged flaws corrected, curves reappear in the hockey stick’s handle, recent temperature changes no longer look unprecedented, and questions return about the extent to which the greenhouse-gas build-up contributes to apparent warming. Scientists eager for political remedies to global warming have so far dismissed challenges to the hockey-stick findings as heresy unworthy of response.

Now, thanks the Barton-Whitfield letter, dodges won’t work. As an answer to political questions, “How dare you ask?” just raises suspicion.

(Online July 2, 2005; author’s e-mail: [email protected])