Impact of Uncertainty of Boundary Conditions on Simulations of the Last Millennium

Tuesday, 16 December 2014: 8:00 AM
Allegra N LeGrande, NASA Goddard Institute for Space Studies, New York, NY, United States and Kostas Tsigaridis, Columbia University, NASA/GISS, New York, NY, United States
Goddard Institute for Space Studies (GISS)-E2-R sampled the broadest range of boundary conditions for simulations of the last millennium, with a dozen different experiments sampling three different volcanic forcing scenarios, three anthropogenic land use change scenarios, and three different solar (TSI) scenarios. This suite of experiment yields 15,000 years of simulations for the last millennium. Here the forcings of these experiments are distilled down into basic fingerprints of each type of change – volcanic, solar, and, anthropogenic land use – to test whether it is feasible to detect these climate changes in various proxy archives. I will illustrate the difficulty in the detection of any of these changes in individual proxy archives, and establish the minimum critieria (given a perfect simulation) to identify solar minima, volcanic eruptions, and large changes in land use. Further, preliminary new results to illustrate the impact of various degrees of sophistication in applying volcanic forcing on the resultant climate signal will be presented.

We will also study the impact of atmospheric composition on climate, by presenting results from atmosphere-only model simulations with the GISS-E2 model, which includes interactive gas-phase chemistry and aerosols at decadal-scale time slices, driven by the millennial-length coupled atmosphere-ocean simulations.