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.

We need to remake the Democratic party. We need to remake America.

We ought to approach this challenge [of global warming] with a sense of profound joy and gratitude: that we are the generation about which, a thousand years from now, philharmonic orchestras and poets and singers will celebrate by saying, they were the ones that found it within themselves to solve this crisis and lay the basis for a bright and optimistic human future.

CO2 is the exhaling breath of our civilization, literally... Changing that pattern requires a scope, a scale, a speed of change that is beyond what we have done in the past.

I think it's harder for people than it should be. But as more and more of us become carbon neutral and change the patterns in our lives to be part of the solution instead of part of the problem, we are now beginning to see the changes in policy that are needed.

Eventually we'll use a CO2 tax offset by a reduction in taxes elsewhere alongside a cap-and-trade plan, but the degree of difficulty associated with a CO2 tax far exceeds that with a cap-and-trade plan. We're seeing it's hard to get a cap-and-trade plan and it's much easier to use as a basis for a global agreement than a CO2 tax.

This is by far the most serious crisis civilisation has ever faced.