Lower climate sensitivity is getting some mainstream discussion. Last week at WUWT, we had this story: BREAKING: an encouraging admission of lower climate sensitivity by a ‘hockey team’ scientist, along with new problems for the IPCC which is now the most read story on WUWT in the past week.
This morning, WUWT carried this essay from Chip Knappenberger: The yearly lukewarm report which spurred some communication from Andrew Rekvin at NYT about the similar story he just posted today: A Closer Look at Moderating Views of Climate Sensitivity.
Andy just sent me a fascinating exchange from Gavin Schmidt of NASA and the Realcimate blog. Gavin sent sent this note as part of a group e-mail exchange and this is what Revkin forwared to me (and has now posted at Dot Earth):
Andy, I think you may be slightly misrepresenting where the ‘consensus’ on this issue has been. While there have been occasional papers that have shown a large tail, and some arguments that this is stubborn – particular from constraints based on the modern tranisent changes – there has always been substantial evidence to rule these out. Even going back to the 2-11deg C range found in the initial cpdn results in 2005, many people said immediately that the high end was untenable (for instance).
Indeed, the consensus statements in the IPCC reports have remained within the 1.5 – 4.5 range first set by Charney in 1979. James’ work has helped improve the quantifications of the paleo constraints (particular for the LGM), but these have been supported by work from Lorius et al (1991), Kohler et al (2010), etc. and therefore are not particularly radical.
By not reflecting that, you are implying that the wishful thinking of people like Ridley and Lindzen for a climate sensitivity of around 1 deg C is tenable. It is not, and James’ statement was simply alluding to that. For reference, James stated that his favored number was around 2.5 deg C, Jim Hansen in a recent letter to the WSJ quote 2.5-3.5 (based on the recent Palaeosens paper), and for what it’s worth the CMIP5 GISS models have sensitivities of 2.4 to 2.7 deg C. None of this is out of the mainstream.
I sent Schmidt and the group this reply:
In policy circles, including popular calculations of emissions trajectories necessary to avoid a high change of exceeding 2 degrees C. of warming, the hot tail has not been trimmed (unless I’m missing something?).
To me, that says the climate science community — including the Intergovernmental Panel on Climate Change science working group — has not adequately conveyed the reality you state here.
Anthony: This essay from Pat Michaels is relevant also: