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.

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 Americans in 2100 came to see 12 meters sea-level rise as inevitable by 2200, who can even begin to fathom how the nation would respond?

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

Would PBS go so far as to give air time to an even more extreme kind of disinformer, a Holocaust denier?

Do believe that if we fail to act in time, it will be the single biggest regret any of us has at the end of our lives.

The first few feet of sea-level rise alone will displace more than 100 million people worldwide and turn all our major Gulf and Atlantic coast cities into pre- Katrina New Orleans - below sea level and facing super-hurricanes.