Dyson's views on global warming were criticized. Climate scientist James Hansen said that Dyson "doesn't know what he's talking about… If he's going to wander into something with major consequences for humanity and other life on the planet, then he should first do his homework – which he obviously has not done on global warming." Dyson replied that "y objections to the global warming propaganda are not so much over the technical facts, about which I do not know much, but it's rather against the way those people behave and the kind of intolerance to criticism that a lot of them have."