Subject:  	Re: The Sunday Times
Date: 	Mon, 11 Jan 2010 16:37:57 +0100
From: 	Stefan Rahmstorf 
To: 	Leake, Jonathan 

Dear Jonathan,

I read your article and find there is a substantial error in it. You
call our PNAS paper "research from the Copenhagen summit" and
"underpinning the Copenhagen talks", but in fact it has nothing to do
with the Copenhagen summit and was not presented or discussed there
(as far as I know - it was however presented by me at the Copenhagen
climate science congress in march, which is the proper place to debate
a scientific study like this). Could you please publish a correction
of this point, which I think is not a minor issue since it serves to
feed suspicions about "politicised science" that are promoted by some
interested quarters.

Another factual correction is that the study was not published by the
Potsdam Institute, rather it is a collaboration of Martin Vermeer from
the Helsinki University of Technology (lead author of the paper) and
myself.

I doubt any negotiators would have been aware of our paper or that it
would have had any influence on them. After all, the debating points
amongst negotiators were not the impacts of climate change but rather
questions of who should do what in mitigation, technology transfer, or
financing of adaptation. The climate target of 2 ºC found in the
Copenhagen Accord has a very long history, e.g. having been adopted in
L'Aquila long before our paper was published. So the idea that a
single scientific paper could have an impact on these negotiations is
utterly unrealistic. And it should not have any impact. Since PNAS
published our paper not long before Copenhagen I was asked at the time
in a radio interview what our results mean for the negotiations, and I
replied: nothing. That's because I think any scientific study needs to
be debated and digested by the scientific community first, before it
is considered by policy makers. The latter should base their decisions
on broad-based science assessments like IPCC, not on the latest
individual paper just published.

By the way, I found your article rather one-sided, since you only
mention a few critics from Britain who found our numbers too high, but
you did not cite criticism from others who find them too low, nor did
you mention the wide acceptance that the semi-empirical method has
found since I first published it in 2007. My impression is that the
latter is the largest group of colleagues by far, see the 70 citations
of the paper, the adoption of its numbers in at least three recent
broad-based assessments (plus the Dutch Delta Commission, which used
it in parts of its assessment to estimate numbers out to the year
2200, against my initial advice but after thorough testing with the
help of comprehensive climate models). There is also several research
groups who have adopted and/or modified the approach in their own
studies, see e.g. refs. 4 and 8 in our paper. So while I welcome any
robust and controversial discussion of our results (in fact we publish
in order to stimulate such discussion), I think the impression that
your article could easily give, namely that everyone but myself thinks
our paper is a methodologically ill-founded piece of alarmist,
politicised science, is incorrect and doesn't inform your readers very
well about the actual state of discussion in the science community.

Best regards, Stefan

ps This is not my only "extreme" piece of science - as you can see in
the IPCC report I have co-authored also an extreme data-constrained
estimate of climate sensitivity: it is the lowest of all 13 estimates
discussed in the report.

-- 
Stefan Rahmstorf
www.ozean-klima.de
www.realclimate.org