GC14A-07
Rate and Velocity of Climate Change Caused by Cumulative Carbon Emissions

Monday, 14 December 2015: 17:33
3014 (Moscone West)
Anna LoPresti1, Steven J Davis1, Noah S Diffenbaugh2, James Tremper Randerson3, Dawn Woodard4 and Allison Charland5, (1)University of California Irvine, Irvine, CA, United States, (2)Stanford University, Earth System Science, Stanford, CA, United States, (3)University of California Irvine, Department of Earth System Science, Irvine, CA, United States, (4)Appalachian State University, Boone, NC, United States, (5)Stanford University, Stanford, CA, United States
Abstract:
International climate mitigation efforts are focused on limiting increase in global mean temperature, which has been shown to be proportional to cumulative CO2 emissions. However, the ability of natural and human systems to successfully adapt to climatic changes depends on both the magnitude and rate of change, the latter of which will depend on how quickly a given level of cumulative emissions occurs. We show that cumulative CO2 emissions of 4,620 Gt CO2 (reached in 2100 in RCP4.5 and 2057 in RCP8.5) produce globally averaged warming rates that are nearly twice as fast in RCP8.5 than RCP4.5 (0.34±0.08°C per decade versus 0.19±0.05°C per decade, respectively). Similarly, the globally averaged velocity of climate change calculated according to the “nearest equivalent climate” is greater by a factor of ~2 in RCP8.5 than in RCP4.5 (2.51±0.67 km y-1 versus 1.32 ± 0.39 km y-1, respectively), despite equivalent cumulative emissions. These differences in the projected velocity of climate change represent uncertainty for ecosystems that may be unable to adapt to the faster changes. Particularly at risk are boreal forests, of which 48% are projected to experience rates of change beyond their expected adaptive capacity (i.e. >0.3°C per decade) in RCP4.5, compared with 95% in RCP8.5. Thus, the same budget of cumulative carbon emissions may result in critically different impacts on natural and human systems, depending on the amount of time over which that budget is expended.