The Sun Isn't the Cause of Earth's Sudden Climate Change, Conclude Scientists

Wednesday, December 26, 2007 by: David Gutierrez, staff writer
Tags: global warming, solar radiation, health news

(NewsTarget) Changes in solar output cannot be the cause of recent global warming trends, according to a study published in Proceedings of the Royal Society, Series A.

The study was spurred in part by "The Great Global Warming Swindle," the TV documentary that featured a hypothesis that increased solar radiation may be causing global warming.

"All the graphs they showed stopped in 1980, and I knew why -- because things diverged after that," said researcher Mike Lockwood of the Rutherford-Appleton Laboratory in the United Kingdom. "[But] you can't just ignore bits of data that you don't like."

According to the cosmic ray hypothesis, increased solar radiation leads to a more powerful magnetic field, which blocks cosmic rays from reaching Earth. Because cosmic rays provide particles around which water vapor condenses to form clouds, a decrease in cosmic rays would thus lead to a drop in cloud cover. This means that more solar radiation would strike Earth, leading to warming.

But the current study showed that solar radiation has actually decreased, not increased, in the last 20 years. This same period corresponds to a rate of warming equal to or even greater than that of the rest of the century.

"This paper reinforces the fact that the warming in the last 20 to 40 years can't have been caused by solar activity," said Dr. Piers Forster, a professor at Leeds University and a significant contributor to the Intergovernmental Panel on Climate Change.

"I do think there is a cosmic ray effect on cloud cover," Lockwood said. "It works in clean maritime air where there isn't much else for water vapor to condense around. It might even have had a significant effect on pre-industrial climate, but you cannot apply it to what we're seeing now, because we're in a completely different ball game."