Local and state governments have outrun the federal government. The EPA has served notice that it will enact a rule requiring CO2 reductions by major emitters in the absence of major legislation. But it's a blunt instrument that is a little more difficult to use than a legislative remedy.

The golden thread of reason that used to be stretched taut to mark the boundary between the known and the unknown is now routinely disrespected.

I've been dreaming of this moment since I was a kid growing up in Tennessee: that one day, I'd have the chance to come here to Madison Square Garden and be the warm-up act for Elvis.

Anyone who deals with the climate crisis has an internal dialogue between hope and despair, because the challenge is so huge and the danger is so great and the stakes are so high. But I have always resolved that in favour of hope, and actually I'm more hopeful now than I was a decade ago when the solutions were visible on the horizon, but you had to seek reassurance that the technology experts that they're coming, they'll be here.

The sooner we switch away from carbon-based fuel and start relying on renewable energy sources available in the United States, the sooner we will grow our economy by creating the millions of new jobs that will come from retrofitting homes and businesses, building smart grids, renewable energy systems and planting trees and all the rest. We need to create a lot of jobs that can't be outsourced.

What we've often seen is that when we Americans say, look, we've got to reduce pollution, business - some businesses complain about it, but almost every time, it's turned out to be easier and cheaper and accomplished faster, and they've gained confidence, and then we go farther.

The entire North Polar ice cap is disappearing before our very eyes. It's been the size of the continental United States for the last 3 million years and now 40 percent is gone and the rest of it is going.