Four decades ago, he spoke out bravely against the Vietnam War. Will he show the same courage today, in helping to end the fossil-fuel era?
 

The growing threats of nuclear war and environmental catastrophe make it hard to bet on the survival of our species.

Allowing polluters to trade carbon could keep poor Californians breathing unhealthy air.

Yes, he said the word “climate”—but he hasn’t committed to any of the big steps needed to avert catastrophe.

On a Farther Shore captures the conservationist’s deep sense of geologic time and the forces of evolution.

"We're not going to outspend the fossil fuel industry," the 350.org founder explains. "We have to find other currencies to work in, and those are the currencies of movements."

If the earth's temperature rises by another 2 degrees celsius, our planet faces mass extinctions.

Awaiting a Keystone decision, environmentalists make a historic vow to engage in mass civil disobedience. 

The latest trend toward fossil fuels is dangerous for the entire planet, since China is the world’s largest emitter of greenhouse gases.

There is something eerily disquieting about Antarctica, where humanity isn’t capable of enduring long.