James Annan is a scientist is a scientist who is a member of the Global Change Projection Research Programme at RIGC. His work is frequently cited in the blogosphere by the activist community, as he more or less declared some years back that atmospheric sensitivity to a doubling of CO2 concentrations was 3C, and he was pretty definitive about it.
The performance of several climate parameters over the past decade has caused him to rethink his view on the subject of atmospheric sensitivity and he posted his newer views on his weblog today.
Money quote: “the additional decade of temperature data from 2000 onwards (even the AR4 estimates typically ignored the post-2000 years) can only work to reduce estimates of sensitivity, and that’s before we even consider the reduction in estimates of negative aerosol forcing, and additional forcing from black carbon (the latter being very new, is not included in any calculations AIUI). It’s increasingly difficult to reconcile a high climate sensitivity (say over 4C) with the observational evidence for the planetary energy balance over the industrial era.”
For Lukewarmers it is welcome support for our views of a lower value for sensitivity.
We’ll get back to Matt Ridley’s questions later.