Sir

Your News in Brief story 'Germany counts the costs of climate change' (Nature 446, 360; 2007) reports the conclusions of a study by the German Institute for Economic Research (DIW) that you state is based on my work. This is not correct. As I had previously documented (R. Roson and R. Tol Integr. Assess. 6, 75–82; 2006), the DIW model is based on egregious misinterpretation of my work.

The German gross domestic product (GDP) was about €2,000 billion (US$2,700 billion) in 2006. If the German economy grows by 1.65% per year without climate change and 0.5% slower with climate change, as the DIW study suggests, then the gap between the two scenarios is the €800 billion in 2050 that you reported. This corresponds to 20% of German GDP in 2050, without climate change. This is at the upper end of the range of the Stern Review. However, you call the DIW study “less pessimistic” than the Stern Review.

You are correct to say that my estimates of the impacts of climate change are lower than those of the Stern Review, and, by implication, the DIW study. Indeed, as I showed earlier (R. Tol Energy Policy 33, 2064–2074; 2005), peer-reviewed estimates are lower than estimates in the grey literature. Neither the DIW study nor the Stern Review were reviewed by independent peers.