A whiff of the Sunday Sport
May 24, 2013
Bishop Hill in Climate: sensitivity, Matt Ridley

Having failed to reply to Matt Ridley's request to respond to Myles Allen's critique, Damian Carrington and his band of merry men have responded with another, but rather grubbier, attack in the same direction, this time from Nuccitelli.

Given that even Nuccitelli's co-authors at Skeptical Science have pointed to his misrepresenting those who disagree with him, and given the car crash of his article about Nic Lewis the other day, a reputable newspaper would steer clear. But when you haemorrhaging money, I guess the priorities are different.

Here's a paragraph from Nuccitelli's article:

[Ridley] suggests, based on outdated references from Bjorn Lomborg, that the economic impacts of climate change are nothing to worry about. Cambridge economist Chris Hope tested this claim by running the climate sensitivity estimates from the new Otto paper in his economic assessment model, PAGE09. The model previously estimated the climate damage from greenhouse gas emissions at an average cost of approximately $100 per tonne of carbon dioxide. The revised estimate resulted in an average cost of $80 per tonne. Given that humans emit over 30 billion tonnes of carbon dioxide per year, that amounts to an annual increase in committed climate change damage of $2.4 trillion, or over 3% of the global gross domestic product, quite contrary to Ridley's rosy perspective.

Line one is, of course, not true. I'm not sure of the precise source for Ridley's quote, but Lomborg made similar remarks about the relatively mild economic impacts of global warming in his evidence to the US Congress on 25 April this year. To describe them as "outdated" is therefore yet another Nuccitelli "embellishment". Lomborg's remarks are very much in the economic mainstream, but of course this will not bother Nuccitelli (or the Guardian) in the slightest.

Chris Hope's $80 estimate is equally problematic. Nic Lewis has pointed out, in a comment that has yet to receive a response from Hope, that the estimate didn't actually use the Otto et al preferred figure of 1.3°C for transient climate response. Moreover, Hope's model seems to estimate the longer-term effects of climate change from the transient climate response and a "feedback response time" rather than a direct estimate of the effective climate sensitivity. In a Twitter exchange with yours truly, Hope explained that his method implied an ECS figure of 2.5°C. Unfortunately, the Otto et al estimate of for ECS was only 2°C (and watch this space for some rather exciting news on this subject). The difference is likely to be important. Earlier this year, I asked Hope to estimate the effect on his model of using a figure of 1.6°C for ECS (the Forster and Gregory value). The answer then came out at just $18. 

It's fair to say then that Hope's estimates are highly sensitive to the value of ECS. Given that his methodology seems to overestimate it, the value of $80 that the Guardian is touting looks to have little credibility.

Not that this will bother them of course. They are living in desperate times and every wild accusation and distortion and embellishment may serve to keep their heads above water for a time. It may even work for a while. Stories of alien landings worked for the Sunday Sport for a time. But only for a time.

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