A paper published today in the Journal of Climate suggests that solar irradiance measurements from the $100 million Solar Radiation and Climate Experiment (SORCE) satellite mission are contradictory and erroneous due to "undetected instrument sensitivity drifts," to the extent that the data should no longer be used to simulate climate and atmospheric changes.
Journal of Climate 2012
How Does the Sun’s Spectrum Vary?
Judith L. Lean
Space Science Division, Naval Research Laboratory, Washington, DC 20375 USA
Matthew T. DeLand
Science Systems and Applications, Inc., Lanham, MD 20706 USA
Recent observations made by the Spectral Irradiance Monitor (SIM) on the Solar Radiation and Climate Experiment (SORCE) spacecraft suggest that the Sun’s visible and infrared spectral irradiance increased from 2004 to 2008, even as the total solar irradiance measured simultaneously by SORCE’s Total Irradiance Monitor (TIM) decreased. At the same time, solar ultraviolet (UV) irradiance decreased 3 to 10 times more than expected from prior observations and model calculations of the known effects of sunspot and facular solar features. Analysis of the SIM spectral irradiance observations during the solar minimum epoch of 2008, when solar activity was essentially invariant, exposes trends in the SIM observations relative to both total solar irradiance and solar activity that are unlikely to be solar in origin. We suggest that the SIM’s radically different solar variability characterization is a consequence of undetected instrument sensitivity drifts, not true solar spectrum changes. It is thus doubtful that simulations of climate and atmospheric change using SIM measurements are indicative of real terrestrial behavior.