Apparent Climate Sensitivity from the Vostok Ice-Core

H S Kheshgi (Exxon Research and Engineering Company, Annandale, NJ 08801; ph. 908-730-2531; fax 908-730-3301; Internet: hskhesh@erenj.com); A G Lapenis (Department of Geography and Planning and Department of Earth and Atmospheric Sinces, State University of New York at Albany, Albany, NY 12222; ph. 518-442-4586; fax 518-442-4494; Internet: alapenis@csc.albany.edu)

The apparent sensitivity of paleotemperature from the Vostok core to components of global forcing of climate is estimated under the assumption that global forcing causes a proportionate change in temperature at Vostok. Records of CO2, CH4 and dust from the Vostok core along with d18O records are used to reconstruct components of global forcing due to CO2, CH4, aerosols and albedo. The inferred Vostok temperature over the time period from 5 kyr to 150 kyr BP is much more closely correlated to components of forcing derived from Vostok records than from reconstructed forcing due to albedo changes which are derived from sea-core records. This leads to a higher apparent climate sensitivity to Vostok-based forcings than to albedo which is sensitive to the choice of time period and resolution. However, since the last deglaciation (5 kyr to 20 kyr BP), during which there is an accurate chronology, reconstructed albedo forcing is closely correlated to the Vostok temperature. Over this time period, the asynchronous behavior albedo forcing and CO2 + CH4 + aerosol forcing allows robust estimation of the apparent partial climate sensitivity to albedo and to CO2 + CH4 + aerosol forcing which are found to both be close to 1 C/(w/m2) at Vostok.