Carbon-free energy is simply something we have to do. The time for talk is past. If we turn around net carbon emissions by 2020 rather than 2040, we get another 2° of fever rather than 3° - and that's a big difference.

It's going to be like herding stray cats, and the political leaders who can do it will be remembered as the same kind of geniuses who pulled off the American Revolution.

Our CO2 mixes with everyone else's within a year, then hangs around for centuries like a shroud.

Stopping emissions growth represents the most minimal of do-something responses.

Even if we stop the growth, we'd still be adding a constant amount of fossil carbon to the atmosphere each year.

Unless we redesign our civilization in numerous ways, all of the science in the world won't save us.

If we don't start thinking big about the CO2 problem, we may miss our opportunity to stop a climate runaway that will trash the habitable parts of the earth.