Sunspots make the world hot and wet

But climate change still down to humans

News that paleoclimatologists at Paul Smith's College in New York state have found a link between sunspot activity and rain reaches us on the same day that other mathematicians at the University of Washington have uncovered a correlation between variations in the global temperature and the cycle of solar activity.

The mathematicians Ka-Kit Tung and Charles Camp looked at satellite data on solar radiation and surface temperatures over the past 50 years. They report a 0.2°C shift in average temperatures across the planet as the sunspot cycle plays out, New Scientist reports (the work is published in Geophysical Research Letters).

This is significant, because although sunspots and surface temperature have been linked before, this is the first evidence of an impact on global temperatures.

The pair has also calculated the specific effect of an increase in heat energy in the atmosphere, and by how much this can change temperature on the ground. Using this information, they have calculated that if atmospheric carbon was doubled tomorrow, the planet would see an increase in temperature of between 2.3°C and 4.1°C.

They say their numbers fit well with the less conservative predictions of climate models, adding credibility to the models themselves.

Although the work of Tung and Camp doesn't paint a particularly rosy picture of our future, the idea that sunspots and rain appear to be linked is proving useful in predicting outbreaks of insect borne disease. The Paul Smith boffins say that over the last century, unusually heavy falls of rain in East Africa have preceded peak solar activity by about one year.

The researchers say they hope people will use the link to make predictions on the ground.

"These results are an important step in applying paleoclimate analyses to predicting future environmental conditions and their impacts on society," said Dave Verardo, director of the National Science Foundation's paleoclimate program, which funded the research. "It's especially important in a region [East Africa] perennially on the knife-edge of sustainability."

If the pattern is reliable, we can expect to see heavy rain in the region in 2010 or 2011, as the 11 year cycle of sunspots reaches its next peak. The rain could herald outbreaks of diseases such as Rift Valley Fever, the researchers say, as mosquitoes thrive in wet conditions. ®

Sponsored: Designing and building an open ITOA architecture