Climate Responses to Total and Spectral Solar Forcing on Decadal and Centennial Time Scales in the GISS/GCMAM

We present results of a series of modeling experiments that explore climate responses to two types of solar spectral forcing with the same variations in total solar irradiance (TSI) on decadal and centennial time scales, one based on prior reconstructions, and another implied by recent observations from the SORCE (Solar Radiation and Climate Experiment) SIM (Spectral Irradiance Monitor). The current version of GISS GCMAM couples atmosphere with ocean, and has a model top near the mesopause, allowing us to examine the full response to the two solar forcing scenarios. We show that atmosphere has different temperature, ozone, and dynamic responses to different solar spectral forcing scenarios even if the variations in TSI are the same. We conclude that that both accurate observations of TSI and SSI are required for better understanding climate response to solar variability.