I've always believed that you should stick as closely to the science as possible. And my biggest advice to reporters has been, if you're doing a climate story, talk to climate scientists. The best climate stories are done by the people who talk to climate scientists.

On our current path, all our great Gulf and Atlantic coast cities are at risk of meeting the same fate as New Orleans.

Replacing half of the U.S. ground-transport fuels with hydrogen from wind power by 2050, for example, might require 1,400 gigawatts of advanced wind turbines or more... replacing those fuels with electricity might require less than 400 GW.

If our government won't spend the money to protect New Orleans sufficiently today, what are the chances we will spend the money to protect dozens of coastal cities post-2050, once everyone knows that sea levels will keep rising and intense hurricanes will occur relentlessly?

The science is crystal clear: we humans are the primary cause of global warming, and we face a bleak future if we fail to act quickly.

On moral grounds, I think that if you believe a certain outcome is a very possible outcome, you have an obligation to tell people that. With global warming, the probability of a bad outcome if we stay on our current emission trends is incredibly high. If you know a bad outcome is likely to happen, what right do you have not to communicate that? You go into a doctor's office, what are they going to do - not tell you the diagnosis?

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.