My climate science blogging brethren have been typing up a storm about Naomi Oreskes’ Dec. 3 Science essay on the consensus about climate change, and amidst all the noise I missed Roger Pielke Jr.’s thoughtful take (he’s quoting here in his blog from a 2001 Nature paper):

Consider once again global climate change. For many years, policy debate has centred on the degree of certainty that decision-makers ought to attach to competing visions of the future climate. Lost in this doomed enterprise is the point that climate will certainly have an increasingly strong effect on the environment and society, simply because of growing vulnerability related to factors such as population, wealth and use of land. If a goal of climate policy is to reduce the effects of climate on the environment and society, then effective action need not wait until we are more certain about details.

Seen in this light, efforts to reduce uncertainty via ‘consensus science’ – such as scientific assessments – are misplaced. Consensus science can provide only an illusion of certainty. When consensus is substituted for a diversity of perspectives, it may in fact unnecessarily constrain decision-makers’ options. Take for example weather forecasters, who are learning that the value to society of their forecasts is enhanced when decision-makers are provided with predictions in probabilistic rather than categorical fashion and decisions are made in full view of uncertainty. As a general principle, science and technology will contribute more effectively to society’s needs when decision-makers base their expectations on a full distribution of outcomes, and then make choices in the face of the resulting – perhaps considerable – uncertainty.

Gavin Schmidt on RealClimate gives his take on Michael Crichton’s new anti-global warming novel. Schmidt’s discussion reads like a fundamental primer on the subject. My favorite bit:

The characters visit Punta Arenas (at the tip of South America), where (very pleasingly to my host institution) they have the GISTEMP station record posted on the wall which shows a long-term cooling trend (although slight warming since the 1970?s). “There?s your global warming” one of the good guys declares. I have to disagree. Global warming is defined by the global mean surface temperature. It does not imply that the whole globe is warming uniformly (which of course it isn?t). (But that doesn?t stop one character later on (p381) declaring that “..it?s effect is presumably the same everywhere in the world. That?s why it?s called global warming”). Had the characters visited the nearby station of Santa Barbara Aeropuerto, the poster on the wall would have shown a positive trend. Would that have been proof of global warming? No. Only by amalgamating all of the records we have (after correcting for known problems, such as discussed below) can we have an idea what the regional, hemispheric or global means are doing. That is what is meant by global warming.

David Appell has been trying to get to the bottom of the discrepancy between Naomi Oreskes’ claim in her Science paper that she had reviewed 928 papers in the ISI database with the keyword “climate change” and Benny Peiser’s claim that there are more than 11,000 such papers in ISI’s “Web of Science.”

Appell is making progress.

More on Latenberg’s Washington Post letter from Michael Mann and Gavin Schmidt.