Letters from the November 24, 2007, issue of Science News

Blame where it’s due

Although multinational agreements on global warming try to spread the burden among all nations, data from the MILAGRO project in Mexico City (“What Goes Up,” SN: 9/8/07, p. 152) suggest that the major responsibility for excess production of greenhouse gases and other pollutants lies with the megacities, which constitute a rather small number of culprits and ones that not all nations possess.