Naturally Interesting

A while back James Hansen, chief climatologist at NASA’s Goddard Institute for Space Studies, published a paper Target Atmospheric CO2: Where should humanity aim? I finally got around to reading it, you should too.

Decreasing CO2 was the main cause of a cooling trend that began 50 million years ago, large scale glaciation occurring when CO2 fell to 425±75 ppm, a level that will be exceeded within decades, barring prompt policy changes. If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm. If the present overshoot of this target CO2 is not brief, there is a possibility of seeding irreversible catastrophic effects.

The most difficult task, phase-out over the next 20-25 years of coal use that does not capture
CO2, is herculean, yet feasible when compared with the efforts that went into World War II. The
stakes, for all life on the planet, surpass those of any previous crisis. The greatest danger is
continued ignorance and denial, which could make tragic consequences unavoidable.

Mr. Hansen uses some pretty strong language, but backs it up with some equally strong data. There is also a Powerpoint presentation available here.