Since Serengeti-scale savanna scenes are only one or two million years old, our earliest after-the-apes ancestors didn't move into this scene so much as they evolved with it, as the slower climate changes and uplift produced more grass and less forest.

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

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.

Anyone who would tackle our current addiction to fossil fuels is going to have to maneuver around denial.

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.

Since Serengeti-scale savanna scenes are only one or two million years old, our earliest after-the-apes ancestors didn't move into this scene so much as they evolved with it, as the slower climate changes and uplift produced more grass and less forest.

You can always spot the pioneers by the arrows in their backs.