The research, conducted by paleoclimatologist Curt Stager of Paul Smith's College in Paul Smiths, N.Y. and colleagues, can be used by public health officials to increase measures against insect-borne diseases long before epidemics begin. The results are published online in the August 7 issue of the Journal of Geophysical Research.
The scientists showed that unusually heavy rainfalls in East Africa over the past century preceded peak sunspot activity by about one year.
"The hope is that people on the ground will use this research to predict heavy rainfall events," Stager said. "Those events lead to erosion, flooding and disease. With the help of these findings, we can now say when especially rainy seasons are likely to occur, several years in advance."
"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."
Sunspots indicate an increase in the sun's energy output, and peak on an 11-year cycle. The next peak is expected in 2011-12. If the pattern holds, rainfall would peak the year before.
Because mosquitoes and other disease-carrying insects thrive in wet conditions, heavy rains may herald outbreaks of diseases such as Rift Valley Fever.
The research relied on rainfall data going back a century. Historical records of water levels at lakes Victoria, Tanganyika, and Naivasha also demonstrated the link.
Stager demonstrated that while the link between sunspots and rainfall seemed to grow weaker from 1927 to 1968, the cyclic pattern held true throughout the 20th Century. Previous statistical analysis discounted the link for a variety of reasons, including the influence of climatic disturbances not
Contact: Cheryl Dybas
National Science Foundation