Environmentalists were aghast when President Donald Trump withdrew the U.S. from the Paris climate treaty, with some declaring that the very survival of our civilization was at stake. But is the Paris accord really all that stands between the planet and the worst of climate change? Certainly not.

This is not to deny that President Trump’s announcement was problematic. He failed to acknowledge that global warming is real and wrongly claimed that China and India are the “world’s leading polluters.” (China and the U.S. are the...