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Scientists believe a link observed between sunspots and heavy rainfall can be used to predict disease outbreaks in East Africa.

In a study, published this week (7 August) in the Journal of Geophysical Research – Atmospheres, researchers observed that the occurrence of extreme East African rainy seasons during the twentieth century corresponded with high numbers of sunspots — dark spots on the sun that indicate an increase in the energy output of the sun.

The researchers looked at the water levels of Lake Victoria and five other lakes in East Africa. They found that approximately one year before the peak of a sunspot cycle, water levels in the lakes peaked due to noticeably wetter rainy seasons.

The researchers suggest that this might be because the higher amount of energy produced by sunspot activity heats the earth, causing moist air to rise and rain to fall.

Because sunspot activity peaks in an approximately 11-year cycle, the researchers believe this information could give authorities an idea of when to prepare for major outbreaks of malaria and Rift Valley fever.

These diseases accompany rainy seasons because mosquitoes and other disease-carrying insects flourish in wet environments.

Dave Verardo, director of the National Science Foundation's paleoclimate programme, which funded the research, said in a press release that the study is an important step in using research into past climates to predict future conditions and how they might impact societies.

"It's especially important in a region [East Africa] perennially on the knife-edge of sustainability," he added. 

Using the climate models, the researchers warn of a major rainy period in 2010, which — if the pattern holds — will precede the next sunspot peak, expected in 2011–2012.

According to lead researcher Curt Stager from the Natural Sciences Division of the US-based Paul Smith's College, the research provides policymakers with information to prepare for the consequences of heavy rains.

"We hope that people who have the know-how and the resources to deal with outbreaks of Rift Valley fever, malaria, and cholera as well as with possible flood-damage to infrastructure can benefit from advance warning," Stager told SciDev.Net.

But, concedes Stager, the predictions can only reliably predict rainfall events due to sunspot peaks, not droughts or rainfall due to less cyclic weather patterns such as El Niño.

Link to abstract of paper in the Journal of Geophysical Research – Atmospheres

Journal of Geophysical Research – Atmospheres 112, D15106 (2007)