In February President Obama said, a little carelessly, that climate change is a greater threat than terrorism. Next week he will be in Paris, a city terrorized yet again by mass murderers, for a summit with other world leaders on climate change, not terrorism. What precisely makes these world leaders so convinced that climate change is a more urgent and massive threat than the incessant rampages of Islamist violence?

It cannot be what is happening to world temperatures, because they have gone up only very slowly, less than...