Mitigation: Major Climate Change Can Be Avoided. Warren M Mitigation: Major Climate Change Can Be Avoided! Warren M. Washington, Reto Knutti, Gerald A. Meehl, Thomas M. L. Wigley, Haiyan Teng, Claudia Tebaldi, David Lawrence, Lawrence Buja, and W. Gary Strand National Center for Atmospheric Research, Boulder CO

Overview Mitigation versus adaptation…if we do nothing about emission then it is adaptation If we go to an low emission mitigation scenario, what does this mean in terms of climate change and impacts

Low Emission Future Climate Change Simulations Can we stabilize global warming using the new CCSP Report 2.1a scenarios? Can we limit global warming to 2ºC from years 1870 to 2100? What are climate change impacts on surface temperature, precipitation, and sea ice?

Actual Emissions vs. Scenario Emissions CDIAC = Carbon Dioxide Information and Analysis Center, DOE EIA = Energy Information Administration, DOE Difference mainly due to difference in how Chinese emissions were estimated. Mike Raupach et al., PNAS 2007

Trajectory of Global Fossil Fuel Emissions 50-year constant growth rates to 2050 B1 1.1%, A1B 1.7%, A2 1.8% A1FI 2.4% 2006 Current emissions are tracking above the most intense fossil fuel scenario established by the IPCC SRES (2000), A1FI- A1 Fossil Fuel intensive; and moving away from stabilization scenarios of 450 ppm and 650 ppm. Observed 2000-2006 3.3% Raupach et al. 2007, PNAS; Canadell et al. 2007, PNAS

Assumptions If conservation, renewables, solar, wind, biomass, and nuclear became a larger component of the energy mix, it is possible that CO2 concentration could be limited to roughly 450 ppm (Level 1 of the new CCSP scenarios) and we could limit warming from 1870 to 2100 to about 2ºC.

Reduction in CO2 Emissions Reference (non-mitigation) Level 4 Level 3 Level 2 Level 1 (mitigation) ~ 70% cut in carbon emissions by the end of century

Impacts Ecology Animals…Polar bears Ocean Permafrost Extremes: Heat waves and water ( flooding and droughts)

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