Robert F. Cahalan
Head of NASA/Goddard’s Climate and Radiation Branch
Temperature Responses to Spectral Solar Variability on Decadal Time Scales
Results from the Solar Radiation and Climate Experiment (SORCE) and its implications for Earth’s energy budget and climate are summarized. We briefly describe a proposed new approach to determine the pre-satellite history of Total Solar Irradiance (TSI) from lunar borehole observations. Then we conider two scenarios of decadal solar spectral irradiance variations – conventional in-phase variations, for which the spectral shape remains unchanged, and out-of-phase variations that are based on SORCE-SIM observations. These scenarios are used to force a tropical one-dimensional radiative-convective model, and the global three-dimensional GISS modelE. Both scenarios and models give maximum temperature responses in the upper stratosphere, decreasing to the surface. Upper stratospheric peak-to-peak responses to out-of-phase forcing are about a factor of 5 larger than responses to in-phase forcing. Stratospheric responses are in-phase with TSI and UV variations, and resemble HALOE observed 11-year temperature variations, while responses to conventional spectral forcing are not consistent with the HALOE observations. Some of these results appear in: Cahalan et al, 2010: Geophys. Res. Lett., 37, L07705, doi:10.1029/2009GL041898.