The current elements text provides options for countries to consider as the long-term goal. Curiously, only one of the options refers to the science of the Intergovernmental Panel on Climate Change. The IPCC science is, in fact, consistent with several possible long-term goals, and in particular with several different end dates. It’s just the background assumptions and choice of gases that differ. However, there is one ironclad requirement for any goal that wishes to limit warming: CO2 emissions must most certainly, at some point, come down to zero. The particular day of reckoning depends upon how much warming and risks … Continue reading The Least-Cost, Least-Risk Long Term Goal