Slate: I have just swallowed my greens–1,000 pages of them–and I am torn. If the planet warms by 6 degrees in my lifetime, as the climatologists say it really could, we will face vast and violent weather of mass destruction. The last time the world warmed so much, so fast, was 251 million years ago–and almost everything on Earth died. So I have no doubt environmentalism is the most urgent ideology left standing, reducing every other disagreement to a second-rank squabble. Yet it is–as an …