Some 3 million years ago, when the earth was a little more than 3°C warmer than preindustrial levels (about 2.2°C warmer than today), Antarctica had far less ice and sea levels were a stunning 25 meters higher than today. If we stay on our current emissions path, the planet will almost certainly be that warm by the century's end.

The world beyond 450 ppm atmospheric concentrations of carbon dioxide, the world that crosses carbon cycle tipping points that quickly take us to 1000 ppm, is a world not merely of endless regional resource wars around the globe. It is a world with dozens of Darfurs. It is a world of a hundred Katrinas, of countless environmental refugees

Since 1955 the oceans have absorbed roughly twenty times more heat than the atmosphere.

Ideology trumps rationality. Most conservatives cannot abide the solution to global warming - strong government regulations and a government-led effort to accelerate clean-energy technologies in the market.

As long as a handful of U.S. scientists, most receiving funds from the fossil fuel industry, get equal time with hundreds of the world's leading climate scientists, the public inevitably ends up with a misimpression about the state of our scientific understanding.

By the end of the third decade of this century, all of American life - politics, international relations, our homes, our jobs, our industries, the kind of cars we drive - will be forever transformed by the climate and energy challenge.

The best thing about improvements in health care is that all the climate-change deniers are now going to live long enough to see how wrong they were.