Another message from the nation’s top climate scientist is out (here). I’ll let Hansen explain the baseball analogy. His bottom line is:
Basic fossil fuel facts (about reserves) must be combined with basic climate facts described in the paper “Target Atmospheric CO2: Where Should Humanity Aim?”. That paper has been submitted to Science and is available in arXiv, the permanent archive for physics preprints. The main paper is here and the Supporting Material is here.
Our conclusion is that, if humanity wishes to preserve a planet similar to the one on which civilization developed and to which life on Earth is adapted, CO2 must be reduced from its present 385 ppm to, at most, 350 ppm. We find that peak CO2 can be kept to ~425 ppm, even with generous (large) estimates for oil and gas reserves, if coal use is phased out by 2030 (except where CO2 is captured and sequestered) and unconventional fossil fuels are not tapped substantially. Peak CO2 can be kept close to 400 ppm, if actual reserves are closer to those estimated by “peakists” (people who believe that we are already at peak global oil production, having extracted about half of readily extractable oil resources)….
A near-term moratorium on coal-fired power plants and constraints on oil extraction in extreme environments are important, because once CO2 is emitted to the air much of it will remain there for centuries.
HANSEN ISSUES A CALL TO ARMS