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

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

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.

Climate change has a very high procrastination penalty that just grows with each passing year of inaction - rather like what happens if you don't pay off your credit card. But for climate, there is no such thing as a fresh start from bankruptcy.

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.

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

Perhaps we should put up posters in such places reminding people that where they stand was underwater the last time that the Earth ran a 3°F fever.