That’s the conclusion of one of the first analyses to explore the relationships among energy use, mid-century targets and long-term policy options, published Monday by the Proceedings of the National Academy of Sciences.
The study establishes the notion of “feasibility frontiers,” the point at which end-of-century goals become unobtainable or increasingly unlikely unless specific mid-century benchmarks are met.
The study also for the first time establishes odds of hitting specific long-term targets. If energy demand remains high, for instance, it finds that even if the world’s governments manage to cut global emissions in half by 2050 and then do everything possible to limit emissions from 2050 on, society has only even odds of limiting global temperature increases to 2º, a goal noted in the recent Copenhagen Accord. “The long-term target discussion, as important as it is, is less important than the interim,” said Michael Oppenheimer, a climate scientist and policy expert at Princeton University. Emissions today are on a path toward 550 ppm or beyond. If a 50 percent emissions cut is deemed too expensive for today’s economies, and emissions instead remain flat for the next few decades – no easy feat in itself – the chances of holding atmospheric carbon dioxide concentrations at 480 parts per million or less evaporate.
http://wwwp.dailyclimate.org/tdc-newsroom/2010/01/disappearing-options