Note on Solar Variability and Climatic Change

Abstract

The sun is a highly variable star, provided we look at it in sufficiently short and sufficiently long wavelengths. Also, radiation in the shorter of these wavelengths has a profound influence on the earth’s atmosphere, provided the layers of the atmosphere which we are examining are 100 km or more above the surface of the earth. The unquestioned accuracy of these two statements does not lead directly to any conclusions concerning the role of solar variability in climatic change, however. The energy in the solar x-ray and radio spectra combined is only a few millionths of the total solar energy. Furthermore, the level in the earth’s atmosphere at which is interrupted the more energetic of these two variables components, the x-ray, is so far removed from the troposphere that linking mechanisms for producing tropospheric effects from the x-rays are difficult to visualize. On the face of it, there seems to be considerably more hope to explain climatic changes from the relatively smaller changes in the energy flux of the solar photosphere—the visible and near infra-red radiation—than from the more variable long and short wavelengths.