Thursday, October 7, 2010

Lower Solar Irradiance, Higher Atmospheric Temps?

The Solar System is so complex! Just when climatologists think they have it figured out, they discover how little they understand. Here's an example:

The thermal structure and composition of the atmosphere is determined fundamentally by the incoming solar irradiance. Radiation at ultraviolet wavelengths dissociates atmospheric molecules, initiating chains of chemical reactions—specifically those producing stratospheric ozone—and providing the major source of heating for the middle atmosphere, while radiation at visible and near-infrared wavelengths mainly reaches and warms the lower atmosphere and the Earth’s surface1. Thus the spectral composition of solar radiation is crucial in determining atmospheric structure, as well as surface temperature, and it follows that the response of the atmosphere to variations in solar irradiance depends on the spectrum2. Daily measurements of the solar spectrum between 0.2µm and 2.4µm, made by the Spectral Irradiance Monitor (SIM) instrument on the Solar Radiation and Climate Experiment (SORCE) satellite3 since April 2004, have revealed4 that over this declining phase of the solar cycle there was a four to six times larger decline in ultraviolet than would have been predicted on the basis of our previous understanding. This reduction was partially compensated in the total solar output by an increase in radiation at visible wavelengths. Here we show that these spectral changes appear to have led to a significant decline from 2004 to 2007 in stratospheric ozone below an altitude of 45km, with an increase above this altitude. Our results, simulated with a radiative-photochemical model, are consistent with contemporaneous measurements of ozone from the Aura-MLS satellite, although the short time period makes precise attribution to solar effects difficult. We also show, using the SIM data, that solar radiative forcing of surface climate is out of phase with solar activity. Currently there is insufficient observational evidence to validate the spectral variations observed by SIM, or to fully characterize other solar cycles, but our findings raise the possibility that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations.

Correspondence to: Joanna D. Haigh1 Email:

Appears in Nature 467, 696-699 (7 October 2010)

Published here on 6 Oct. 2010


Anonymous said...

Alice, GREAT Post! So many of the evangelicals in Christendom focus way to much the emotional aspect of worship, why do you think this is? I understand that they have left the core values of Christianity, but are we just trying to be more relevant to culture or just plain heretical? Where could I get good reading material on this. I am an Anglican who is seemingly dealing with this sort of thing (praise bands), and why do Christians think that taking the Eucharist could be misunderstood as making people feel like outsiders? I don't understand, this is the MOST important thing we do on Sundays. Help me understand.
Dave Abshear

Alice C. Linsley said...


You will find several readings helpful in sorting tis out. You will find them here:

Best wishes,