SOLAR VARIABILITY AND CLIMATE CHANGE
Ms. Sallie Baliunas
Harvard-Smithsonian Center for Astrophysics
Monday, April 17, 3:30 pm
Ben Bandy Conference Center
Center for Applied Energy Research
Recent evidence for the sun's influence on climate change comes from modern measurement programs and computer simulations of the climate. Not only correlations between solar variability and climate change but also mechanisms underlying them are being studied.
One possible mechanism driving climate change is total irradiance change of the sun. Satellite measurements for nearly two decades show that the sun's total irradiance changes in step with the 11-year sunspot cycle.
Solar variations are generally only crudely predictable, thus leaving us with direct measurements over too short and interval to study properly the solar influence on climate change over time scales of centuries.
But studies of sun-like stars can yield information on solar variability over such time scales. At Mount Wilson Observatory the surface magnetic activity of sun-like stars has been monitored for over 30 years. These records detail the counterpart of the 11-year sunspot cycle in stars close in mass and age to the sun. In parallel, observations of brightness changes in sun-like stars have been made for over a decade. Considered together, these records on surface magnetism and brightness changes in sun-like stars yield estimates of solar variations over centuries.
Those estimated brightness variations have been studied in computer simulations of the climate which suggest that the solar irradiance change explains at least 50% of the variance of the changes in global surface temperature over the last 100 years.