The Science of 350, the Most Important Number on the Planet
Courtesy 350.org
By Bill McKibbon
350 is the most important number on the planet.
Which is odd, because until about 22 months ago no one even knew it mattered.
But that’s when, in December of 2007, NASA’s Jim Hansen gave a slide show at the American Geophysical Union annual meeting in San Francisco. He’d been thinking about what it meant that we’d just come through a summer of very rapid ice melt in the high Arctic, and that researchers were reporting “ahead of schedule” changes in dozen other of the earth’s big physical features–melting glaciers, acidifying oceans and so on.
Combined with reams of paleo-climate data, his team believed they now had enough information to finally draw a red line for the planet: when atmospheric concentrations of carbon dioxide were above 350 ppm, they said, global warming would be dangerously out of control. In fact, they said in the abstract of the paper they soon published, above 350 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. Hansen’s data shows that as a planet we’d need to get off coal by 2030 in order for the planet’s forests and oceans ever to bring atmospheric levels back down below 350–that’s the toughest economic and political challenge the earth has ever faced. Click here to read the full article at its source.
