by Allan Taylor

Created on: November 25, 2008

I shall rephrase this question. Is the sun a major factor in causing climate change?

The answer is YES and I shall endeavor to explain the current thinking on the subject.

Global warming is now more commonly called "climate change", which can include global cooling. Also, I don't wish to blame the sun because it can't help doing what suns and planetary systems have to do, by virtue of their existence. Do we blame dogs for barking?

The correlation of sun spot activity to climate was first reported by Sir William Herschel in 1801 who noticed a relationship between solar activity and the price of wheat, from the data given in Adam Smith's book "The Wealth of Nations" published in 1776.

The radiation from our sun is the ultimate source of energy and warmth on earth. Our atmosphere and the earth's surface is continually bombarded by a wide range of electromagnetic radiation, protons, electrons and cosmic rays, which emanate largely from our sun but also from outer space. The intensity of this radiation varies with sun spot activity which are enormous electromagnetic storm regions that are observed to develop periodically on the surface of the sun.

Historical observation of sun spot activity has shown it to be roughly cyclical in nature, time wise. The interval between maxima is about 11 years and for the big solar cycle of 100 years there are 9 individual 11 year cycles. Why this should be so will be speculated upon later.

The actual variation of the sun's total flux of electromagnetic radiation is very small, only a few tenths of a percent which directly can not adequately account for global warming and cooling. There is not a uniform change with all wavelengths from UV, visible and IR radiation etc. Some wavelengths may be more effective than others. However, what is important is whether or not a "multiplier effect" exists and how it may work.

The degree and nature of cloud cover is thought to be very important in determining global and regional temperatures and so climate change. On the micro scale animals and humans automatically know this on hot, cloudless days, by seeking the cooler shade of a bushy tree or by staying in doors in our homes where the sun's warming rays can not penetrate directly.

On the macro scale, the same phenomenon seems to happen when high altitude cloud (cirrus) develops and persists. Cirrus cloud consists of highly reflective ice particles (temperatures ca minus 50 degrees C) and reflect the sun's heat away from the earth, thus promoting a cooling

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