The real negotiation is between humans on the one hand and chemistry and physics on the other. And chemistry and physics, unfortunately, don't bargain.

The fight around climate change, which I've spent my life on, is somewhat more difficult than gay marriages because no one makes trillions of dollars a year being a bigot, and that's how much the fossil-fuel industry pulls in pumping carbon into the air. But the principle is the same, I think.

A third of summer sea ice in the Arctic is gone, the oceans are 30 percent more acidic, and since warm air holds more water vapor than cold, the atmosphere over the oceans is a shocking five percent wetter, loading the dice for devastating floods.

If you look at the polling data, long before anyone had thought about Iraq, it was the [George W.] Bush Administration's decision in the first few weeks in its tenure in office to abnegate the Kyoto treaties that set our international perception into a nose-dive. People around the world looked on in amazement as the biggest part of the problem decided it wasn't going to make any effort to help with the solution.

It's our own throat that we are cutting in the end along with everyone else's. We need to be exercising precisely the kind of leadership that might allow us to nudge China and India, say, onto different energy trajectories, in order to improve our own chances of surviving this century.

We also have to engage - and I think this is important - in national politics because there is no way to address questions of this scale in the short time that we have to address them without engaging in real political change.

We can no longer imagine that we are part of something larger than ourselves - that is what all this boils down to.