On the train this weekend, I was sitting accross the aisle from a lady reading George Monbiot's new book.
Every few minutes, she put the book down and loudly pontificated on global warming. We should all stop flying, of course, and carbon emissions should be set at a world level (!) with everyone given the same individual ration (never mind the economics or enforceability of that one...).
I was sorely tempted to point out the error of her ways, when her husband stepped in and did the job for me. Eager to get on with reading his own book, he said: "You know darling, there would be a lot less carbon dioxide in the atmosphere if people would just shut up!"