It was surprising to read the article, “ >Climate change threatens food production ” (Sept. 4), which gives the impression that carbon dioxide is a pollutant. It is not a pollutant, and the original letter in Nature Climate Change does not use this word. It only says that nitrate assimilation was slower under elevated than ambient CO and this would affect food production. The word pollutant refers only to substances which do not occur naturally in the atmosphere. There is a distinction between saying that CO will affect nitrogen assimilation and labelling CO as a pollutant. This distinction must be kept in mind while interpreting scientific results for the public.
S. Raghavan,
Chennai
