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Discussion About the Possible Effects of the Solar Activity upon the Radiation Balance

Jan Olof Jonson
Year: 2010 Pages: 38
Keywords: Galactic cosmic ray, greenhouse effect, solar radiation, solar cycle
This paper is written as a bachelor thesis work at Stockholm University. It is a preliminary manuscript, based upon a more extensive version, shown on this website earlier. Please note the copyright rules with respect to the figures.

The paper has now after that a substantial reduction of the content has been undertaken,  been accepted as a BS thesis at Stockholm's University (April 27, 2012). The BS thesis paper is available through the author, E-mail address jajo8088@student.su.se

In searching for the reasons behind the rising temperature a broad scope of potential triggering factors is currently investigated by the scientific community. Among those are the effects of extraterrestrial origin. For the time span of the last one-and-a-half century it has been shown that there is a negative correlation between the solar activity and the temperature in the Northern Hemisphere. However, beginning with the 1990's, the overall temperature rise has increased to the extent that the scientific community has felt the need to search for new models capable of explaining this new phenomenon. As a physical explanation, variations in the irradiance from the sun have also been considered, but the effects have appeared to be too small to offer a complete explanation of the observed temperature rise.

Secondary effects of the solar activity have also attained increasing interest. It has among others been assumed that the Galactic cosmic ray flux affects aerosol formation, as decreased solar activity would allow for a deeper intrusion of cosmic rays into the Earth's atmosphere, which in turn is predicted to lead to an increase of the amount of condensation nuclei. Historic records further show that increased cloudiness namely corresponds to a decrease in the solar constant. Higher amount of aerosols leads to higher planetary albedo, and, accordingly to a lower temperature.

The effects of varying cosmic rays have been estimated to be of the same order as the radiative forcing of the increase of carbon dioxide since 1750. Given our knowledge today it is still difficult to judge which the main forcing effects behind the increased temperature are. The results that have been attained tend to corroborate the assumption that Galactic cosmic rays have the effect on temperature, as proposed above. However, there is also a partial ambiguity of the results, which points to the need for further investigation of the field. How each proposed variable affects cloudiness and temperature must further be explored and a serious effort is needed to attain the ?final formula'