Is climate science ‘settled’?

"Rigidly promulgating the idea that climate science is 'settled' (or is a 'hoax') demeans and chills the scientific enterprise."
September 23, 2014

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The claim that “climate science is settled,” which runs through today’s popular and policy discussions, is misguided, says computational physicist Steven E. Koonin*, Director of the Center for Urban Science and Progress at New York University, writing in The Wall Street Journal Friday.

“It has … distorted our public and policy debates on issues related to energy, greenhouse-gas emissions and the environment … and inhibited the scientific and policy discussions that we need to have about our climate future.”

He notes that “the impact today of human activity [on climate] appears to be comparable to the intrinsic, natural variability of the climate system itself,” and that “”we are very far from the knowledge needed to make good climate policy.”

Forecasting the next century

Koonin advises that the crucial, unsettled scientific question for policy is, “How will the climate change over the next century under both natural and human influences?” Answers to that question, he says, “should inform our choices about energy and infrastructure.”

Koonin mentions three measurement unknowns: future human additions to carbon dioxide in the atmosphere as a percentage of natural variability, how the oceans will change and how that will affect climate, and feedback between variable like the direct heating effect of carbon dioxide, which involves water vapor, clouds, and temperature — which “cannot be determined confidently from the basic laws of physics and chemistry, so they must be verified by precise, detailed observations that are, in many cases, not yet available.”

He also points out that the ensemble of some 55 different complex computer models that the IPCC uses provide widely varying descriptions of key variables, such as the past century’s global average surface temperature, which varies by more than three times in the entire warming recorded during that time.

“Rigidly promulgating the idea that climate science is ‘settled’ (or is a ‘hoax’) demeans and chills the scientific enterprise, retarding its progress in these important matters. Uncertainty is a prime mover and motivator of science and must be faced head-on. It should not be confined to hushed sidebar conversations at academic conferences.”

* Formerly undersecretary for science in the Energy Department during President Barack Obama’s first term, professor of theoretical physics and provost at Caltech, and chief scientist of BP.