Aerosol radiative forcing and climate sensitivity deduced from the Last Glacial Maximum to Holocene transition

Abstract

We use the temperature, carbon dioxide, methane, and dust concentration record from the Vostok ice core to deduce the aerosol radiative forcing during the Last Glacial Maximum (LGM) to Holocene transition and the climate sensitivity. A novel feature of our analysis is the use of a cooling period between about 42 KYBP (thousand years before present) and LGM to provide a constraint on the aerosol radiative forcing. We find the change in aerosol radiative forcing during the LGM to Holocene transition to be 3.3 ± 0.8 W/m2 and the climate sensitivity between 0.36 and 0.68 K/Wm-2 with a mean value of 0.49 ± 0.07 K/Wm-2. This suggests a 95% likelihood of warming between 1.3 and 2.3 K due to doubling of atmospheric concentration Of CO2. The ECHAM5 model simulation suggests that the aerosol optical depth during the LGM may have been almost twice the current value (increase from 0.17 to 0.32). Copyright 2008 by the American Geophysical Union.