Michaels misquotes Hansen

Pat Michaels (under the guise of the Greening Earth society) is particularly fond of misquoting Jim Hansen, director of the NASA GISS laboratory (and in the interests of full disclosure, GS’s boss).

Recently he claimed that Dr. Hansen has now come around to the ‘skeptics’ (i.e. Pat Michaels) way of thinking and suggests that they agree on the (small) amount of warming to be expected in the future. Michaels quotes Hansen from a 2001 PNAS paper:

Future global warming can be predicted much more accurately than is generally realized … we predict additional warming in the next 50 years of 3/4 +/- 1/4°C, a warming rate of 0.15 +/- 0.05°C per decade.

However, as is usual in these cases, the ‘…’ hides most of the point. The full quote is:

Given these constraints on climate forcing trends, we predict additional warming in the next 50 years of 3/4 +/- 1/4°C, a warming rate of 0.15+/- 0.05°C per decade.

What are these constraints that Hansen mentions? Precisely the control of CO2, methane and black carbon emissions that Michaels insists are unnecessary!

The fundamental difference in opinion (which has not changed since Michaels and Hansen started debating each other in 1988) is that Hansen (and the vast majority of relevant experts) think that climate sensitivity (how much the globe will warm under a doubling of CO₂) is around 3 (+/-1) °C, while Michaels thinks that it is much less (<1°C). Thus when Michaels ‘predicts’ a warming of a further 1°C by 2050, this is in the absence of any controls on greenhouse gas emissions. On the contrary, Hansen projects a similar change under the assumption that controls WILL be put in place. Thus under the same assumptions as Micheals, Hansen would project a much larger warming.

The suggestion that Hansen has some how come around to Pat Michaels’ way of thinking is simply not true.

Update: Steve Milloy makes a similarly erroneous point commenting on another recent paper (PNAS, 2004) on the same topic

Hansen and Sato are actually talking about trace gases other than CO2 here and that’s where it becomes interesting. Essentially, the ‘father of global warming,’ James Hansen, admits that near-doubling atmospheric CO2 will have negligible effect on global climate – an increment of <1°C. So, after all this time and money, he now agrees with Michaels? What a silly game this is.

Since Hansen has been talking about all the different forcings for a while now (see above) and does not think that climate sensitivity is anywhere near 1°C (let alone less), one might question who is actually playing silly games.