"Solar Forcing of Climate - The Previous Millennium, the Coming Millennium"
Numerous empirical associations suggest that the climate system has been responding to solar forcing on multiple time scales throughout the past millennium. Despite this growing empirical evidence, solar forcing of climate remains enigmatic because neither the extent of long-term irradiance variability, nor the magnitude of climate change, nor the responsible geophysical mechanisms have been well specified as yet. Changes of order one tenth percent in total solar radiative output recorded by space-based observations during the past 23 years are insufficient to account for the empirical associations with the processes simulated by current general circulation climate models. Furthermore, solar forcing occurs in concert with other climate forcings and is superimposed on natural climate variability, making unambiguous attribution difficult. This talk will summarize purported Sun-climate relationships during the past millennium, describe current understanding of solar irradiance and climate variability, and climate responses, and speculate about the implications for the future.