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.

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.

When people ask me what they should do, I reply, "Get informed, get outraged, and then get political."

Conservatives... are so opposed to government regulations that they are skeptical of anyone who identifies a problem that requires regulatory solutions - and they are inherently accepting of those who downplay such problems.

The entire western Siberian sub-Arctic region is melting, and it has all happened in the last three or four years.

The great political tragedy of our time is that conservative leaders in America have chosen to use their superior messaging and political skills to thwart serious action on global warming.

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.