If your goal is keeping the earth’s temperature rise below 2°C, the only thing you have left is hope. Hope that the climate sensitivity—how much the global temperature rises from an increase in greenhouse gas concentrations—is far beneath what the climate models calculate it to be. When it comes to trying to use emissions cuts to achieve the 2°C goal, the cat is already out of the bag—maybe not in terms of emissions-to-date, but almost certainly so for emissions-to-come.
Such is the conclusion implicit in the recent analysis by Joeri Rogelj and colleagues published in a recent issue of Nature magazine.
Rogelj et al. did yeoman’s work in collecting all the varied (non-binding) efforts pledged by all of the various countries of the world to reduce their greenhouse gas emissions under the Copenhagen Accord that came out of last December’s big United Nations Climate Conference.…