Saturday, December 27, 2008

The Solar Connection

The amount of energy recieved from the sun varies over time at an 11 year frequencey as can be seen on the chart. Specifically, total solar irradiance cycles from approximately 1365.4 Watts/meter^2 to about 1366.4. This relatively small variation amounts to approximately 0.075% from peak to trough. In other words, not much!

Application of the Stephan-Boltzmann law shows that these variations correspond to about 0.05 degree C of temperature change. This chart is a good example of how easy it is to make mole hills look like mountains.

It should also be pointed out that longer term variations in the sun's irradiance are known. Notice how the minimum values are trending towards progressively lower values. Over the 22 years from the first valley in 1986 to the last in 2008, the change amounted to 0.12 Watts. This is equivalent to 0.0003 degree C / year; which is insufficient to counter the warming from increases in greenhouse gases.

Another interesting observation is that record high average annual global temperatures tend to occure shortly after solar minimums. Following the 1986 solar minimum, 1987 established a new record high global temperature. Similarly, following the 1996 solar minimum, 1997 and 1998 each established new record high temperatures.

So, although the next solar cycle is not expected to be as great as recent ones, the initiation of the cycle by itself may be associated with another record high average annual global temperature.

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