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?

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?

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.

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.

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?

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.

The coal plants that will be built from 2005 to 2030 will release as much carbon dioxide as all of the coal burned since the industrial revolution more than two centuries ago.