It takes some variety of wilful ignorance to dismiss the need for action to avert the threat of climate change.

From imaginings of vast conspiracies to complacency that global warming can only be benign, the arguments against taking the danger seriously are rooted in a refusal to face reality. The climate is a complex system, of course, and forecasting it fraught with uncertainty. But the evidence is strong enough to make it clear that the risk of catastrophe cannot be dismissed.

Yet advocates of action on climate change often display their own varieties of irrationality. The campaign for universities, charities, local governments and others to sell their holdings in fossil fuel companies, which has been gathering momentum in recent years, is a case in point.