Why Copenhagen matters

In December of 2007, NASA's James Hansen presented his conclusions. According to climate activist Bill McKibben, Hansen has given a simple measure of what is happening to the planet.

...above 350 [ppm of atmospheric carbon] you couldn't have a planet "similar to the one on which civilization developed and to which life on earth is adapted."

It's as if we suddenly discovered what normal body temperature was, so we'd be able to tell when we were running a fever. In that sense, it came as a great relief.

But in every other sense, it was a pretty devastating number. For one thing, we're already past it, at 390 ppm and rising two ppm annually--that's why the Arctic is melting. For another thing, it means the work nations and individuals must do to reduce their carbon footprints is much larger, and must happen much more swiftly, than we'd believed...

Are Hansen and McKibben right? Most of us aren't equipped to know. Those of us not on coal company payrolls or angrily dismissive of "smarty pants" opinion have to believe the scientific consensus that human-caused activity is driving global warming.

Are we, collectively, going to do anything about it? It feels insane to even be asking that question.