Solar Irradiance: Earth’s Energy Source

Earth’s energy emanates from the Sun, a variable star. Solar irradiance heats Earth’s surface and atmosphere, initiating myriad chemical, radiative and dynamical processes that establish Earth’s surface climate, stratospheric ozone layer, upper atmosphere thermosphere and its embedded ionosphere. Changes in solar irradiance over the past century have been suggested to cause climate change that is a significant fraction of industrial-era warming… or so small as to be undetectable.

Now, with more than forty years of space-based observations of solar irradiance and multiple geophysical quantities, and extensive advances in modeling solar irradiance and terrestrial variability, we can clarify with greater certainty the extent to which changes in solar irradiance alter Earth’s environment, from surface to space, in the present space era and the pre-industrial past. Projecting this understanding to upcoming decades permits speculation of C21st global climate change, recovery of the ozone layer and future space environment impacts on earth orbiting spacecraft. This talk summarizes current observational evidence for solar irradiance variability and relates this variability to the Sun’s magnetic activity cycles that produce bright faculae and dark sunspots. Models of solar irradiance variability constructed from current observations are extended into the past and future, and used to quantify the Sun’s role in global climate change, ozone-depletion and recovery, and space environment climatology.