What’s so scary about climate change? The term is not scary — at last not in a visceral, skin-crawling sense. Scientists have shown that the likely 2 degrees of global warming to come this century will be extremely dangerous, but, you know, “2 degrees” is hardly a phrase from nightmares and horror films. How about “rat explosion”? As the climate warms, rats in New York, Philadelphia and Boston are breeding faster — and experts warn of a population explosion. Like rats, humans are hardy animals, and we’ve adapted to all kinds of climates.