Abstract for talk, "Dangerous" Climate Change and Climate Policy" by Michael Oppenheimer

The timescales and lags associated with the physical, biological, and technological responses inherent in the climate system indicate the need for near term policy responses guided by a long term policy framework. For instance, Article 2 of the UN Framework Convention on Climate Change enjoins the Parties to avoid �dangerous anthropogenic interference with the climate system�. Defining �danger� reaches beyond natural science. Questions arise as to what scale of impacts may be considered dangerous, as well as what metric to employ is their quantification. Some potential impacts, e.g., loss of unique cultures such as those of the Arctic or island nations, may defy quantification yet may nevertheless be considered �dangerous�. The distribution of impacts and resulting equity issues also merit careful scrutiny. One approach to defining danger relies on the potential vulnerability of Earth�s large ice sheets. Recent evidence indicates that both ice sheets are shrinking faster than indicated by models, raising the possibility of substantial deglaciation on a timescale of centuries rather than millennia as previously thought. I argue for an initial, precautionary definition of �danger� based on preserving the West Antarctic ice sheet. Given uncertainties in our understanding of ice sheets, this approach suggests 20C global warming above recent temperatures as a benchmark for long term climate policy.