Global warming, we're often told, is an issue we must address for the sake of our grandchildren. We need to cut carbon because of our moral obligation to future generations.

But according to Bill McKibben, that's a 1980s view. As McKibben writes in his new book Eaarth: Making Life on a Tough New Planet, the increasingly open secret is that global warming happened already. We've passed the threshold, and the planet isn't at all the same. It's less climatically stable. Its weather is haywire. It has less ice, more drought, higher seas, heavier storms. It even appears different from space.

And that's just the beginning of the earth-shattering changes in store—a small sampling of what it's like to trade a familiar planet (Earth) for one that's new and strange (Eaarth). We'll survive on this sci-fi world, this terra incognita—but we may not like it very much. And we may have to change some fundamental habits along the way.

Eaarth, argues McKibben, is our greatest failure.

Bill McKibben is a former staff writer for the New Yorker magazine, and author of the famous 1989 book The End of Nature, as well as over a dozen other works. He is currently a scholar in residence at Middlebury College in Vermont, and founder of the global warming grassroots organization 350.org, which lobbies for tougher climate policies. In 2009, the group conducted what CNN later called "the most widespread day of political action in the planet's history."