Think of everything you know about global warming. Think, especially, of the sense you might have that there are twenty, thirty, fifty years left before the Earth’s levels of climate change become truly catastrophic. Now, think again. We’re already there, says Bill McKibben in Eaarth (Times Books, $24.00), an eloquent and passionate call to action. In fact, says McKibben, we’ve changed our planet so much that we can no longer think of it as Earth: now it’s Eaarth, a place of melting ice caps, expanding tropics, and increasingly dramatic “weather events”. And we have to learn to live there.
     McKibben should know what he’s talking about. A leading journalist and environmental activist, he’s been writing on this subject for more than twenty years. In 1989, his The End of Nature was the first book on global warming for a general audience. In the past two years, his nonprofit 350.org has mobilized millions of people across the world to combat climate change.
     In Eaarth, he makes no bones about how serious the situation has become. We’ve already raised the temperature of the planet by one degree Celcius, he writes; as a result, the Arctic ice cap is 1.1 million square miles smaller, and (since warmer air holds more water vapor) global rainfall is increasing by 1.5 percent a decade. But this isn’t just a book full of dry statistics. McKibben is expert at explaining, lucidly and frankly, just what the numbers mean, and what we can do about them. “Forget the grandkids,” he writes. “It turns out this was a problem for our parents.”