The link between the seasons and the Sun is pretty obvious on a blazing July day: more sunlight means hotter weather. But the link between the amount of sunlight and Earth's climate is a bit more complicated and subtle than that. Changes in the Sun's energy output may create regional or even global changes in Earth's climate.
The Sun's overall energy output varies on an 11-year cycle. At the cycle's peak, the Sun's magnetic field produces more sunspots and explosions of energy and particles. The Sun also grows a tiny fraction of a percent brighter. That extra energy warms Earth's outer atmosphere, causing it to expand, which creates extra drag on orbiting satellites. Some of that energy also reaches the surface, warming the whole planet by a fraction of a degree.
But a couple of studies released last year showed that there might be more pronounced effects on a regional scale.
One study found that Africa is more likely to see drenching rains about a year before the peak in the solar cycle. Another study found that there can be good-sized variations in temperature from region to region. During the last "solar maximum" in 2004 and 5, for example, the central U.S. grew about half a degree warmer than the country as a whole.
Several spacecraft will monitor the Sun and its interaction with Earth as we head toward the next peak in the solar cycle, around 2012.
More about the Sun tomorrow.
Script by Damond Benningfield, Copyright 2008
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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