I noted in an update to the the "Stern Exposed" thread that Chris Hope said that he had found an error in Peter Lilley's article about the Stern Report. Lilley has now added a comment pointing out what has happened. I'm reproducing it here.

I have posted this response to Chris Hope's query on his website:

Dear Chris
Thank you for querying the figures I attribute to the PAGE2002 Impact Assessment Model.
In fact the figures I quote do come from your model – Figure 5 on page of your explanatory article The Marginal Impact of CO2 from PAGE2002: An Integrated Assessment Model Incorporating the IPCC’s Five Reasons for Concern. They are line 7 and refer to India so my paragraph should have read:

“The model is given a range of assumptions of impacts on the GDP of each geographic area for a 2.5°C rise in temperature. Thus, IN INDIA a 2.5°C temperature rise is deemed to reduce GDP by between 1.5% and 4% - with a median 2% loss. The loss is then set to increase as a power of temperature ranging between linear and cube – averaging 1.3.”

The words IN INDIA somehow got erased and I will reinstate them in future versions especially as it then makes more sense.

You also single out India in your excellent presentation to the Yale Symposium – page 48 where you point out that though “adaptation reduces impacts by 90% in OECD countries” it reduces it by only “50% in India”. That was the point I was referring to in the second quote to which you refer. Please correct me if I have misinterpreted your model, but as I understand it, even when India and other poor countries which constitute the bulk of the world reach current OECD levels of development they will still be deemed to adapt only by 50% not by 90%?

I am sorry if you thought I was trying to misrepresent your model. Far from it. The clarity and transparency with which you present all your assumptions and equations stood out as a model which I only wish others on all sides of this debate would emulate. So I regret all the more that a proofing error – mea culpa – led to that impression.

Best regards

Peter Lilley