I'll do something a little more substantive on this tomorrow night, but I had a powerful image come up early in the talk that seems worth relating.

Elizabeth was talking about the Greenland Ice Sheet. It's too warm, now, for the ice sheet to form. It has sustained itself because it is cold enough that it doesn't melt away, and enough new snow falls onto it to actually build some parts of it each year (although we are suffering net loss of ice there). But in today's climate, and the climate of the last ten thousand years,it would not get built.

Last week, it snowed on us in Washington, and we experienced very low temperatures for a few days after that. Well, snow is rare for us, and so we played in it and with it, and made snow sculptures and snowballs. Some of that snow we'd sculptured -- and turned into ice balls -- stayed with us for literally days after the untouched surface snow was melted and rained off.

But it's not there now.

The ice sheet holds so much water that if it all melts away, we could see a twenty-foot rise in sea level.