I sometimes feel sorry for politicians. The other day, Ed Miliband, Britain’s bright young energy and climate minister, urged concerned citizens to stiffen the sinews of their political masters in the fight against global warming. With exquisite timing a bunch of climate change activists promptly set up camp on the runway of London’s Stansted airport, stirring the wrath of thousands of delayed air travellers. We can assume that this was not the sort of public-spirited action the minister had had in mind when he told The Guardian newspaper that “popular mobilisation” would empower politicians to take the hard decisions needed to create a low-carbon global economy.