From Bryn Glover, Kirkby Malzeard, North Yorkshire, UK
Your point that methane has less impact as a greenhouse gas than carbon dioxide overall may be true over a timescale of centuries, but given that humanity has only a couple of decades to get its act in order, I would have thought that we need to pay much more attention to the significantly greater short-term effects of the gas than the original article implied (27 April, p 20).
