The Sun and Earth's Climate

The effects of space weather on Earth's climate are currently still a controversy. The idea that solar activity affects climate on our planet is a given, considering that the sun is our source of energy and heat. We are all familiar with a cloudy and rainy day and its colder temperatures as opposed to a sunny, warm day. But does solar activity affect climate in the long run?

One idea was that sun spot activity could relate to changes in short term weather cycles and long term climate changes. In the beginning of the 20th century some scientists concluded that higher sun spot numbers contributed to a rainier and colder weather in some areas of the planet. Others claimed that more sun spots meant a brighter star and hence more heat on Earth. [1]

While short term effects on weather could be eventually verified, this was not the case with long term climate changes, so speculations on this matter went even further. Slight changes in solar radiations were blamed for ice ages on Earth, to the extent that such changes were mentioned in textbooks as possible causes for ice ages, shifts in ocean currents and volcanic dust. [2] These speculations were unconfirmed as soon as the space age started and spacecraft were able to measure ultraviolet radiation, which turned out to fluctuate during high peak solar activity, however which are not able to pass through the stratosphere and have an impact on the climate. Solar wind was also blamed for climate changes. It was suspected that high energy particles generated by solar wind could have an impact on the climate. [3]

In 1980 NASA tried to solve the mystery of the solar constant and its effect on climate by adding a special instrument to a satellite. This instrument detected small variations in the constant, depending on the number and position of sunspots. [4] Since the only assumed way solar activity could affect climate was in the amount of the sun’s output of energy, more and more scientists focused on this idea. During the Nineties, scientists focused on other similar stars and noticed their output of energy varies. As it later turned out, those stars were not so similar to ours after all. [5] With the beginning of the 21st century the increase in global temperatures over the previous century were yet again blamed on solar activity. With the help of numerous satellites, accurate sea surface temperatures were taken and a connection between temperature small variations and the 11 years solar cycle were noticed. [6]

I believe that so far very small influences of solar activity on the climate were revealed, and it does not seem that solar activity would be the main engine behind climate change on Earth. So far human activity has proven a much stronger engine that drives climate changes. Since there is not much we can do to influence solar activity, but there is a lot we can do in terms of our behavior and activities, we should definitely put more energy into that in regard to climate change. Solar activity has other strong effects on our planet and it is important to understand how these work and what we can do to prevent such issues.
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Notes:
[1]
American Institute of Physics. Changing Sun, Changing Climate?  February 2013. http://www.aip.org/history/climate/solar.htm (accessed April 26, 2013), para. 4-6.
[2] Ibid, para. 10-11.
[3] Ibid, para. 13.
[4] Ibid, para. 36.
[5] Ibid, 41.
[6] Ibid, 47.