American Geophysical Union - Paul Smith's College Joint Release

6 August 2007 AGU Release No. 07-19 For Immediate Release

Sunspot abundance linked to heavy rains in East Africa

AGU Contact: Peter Weiss

+1 (202) 777-7507

pweiss@agu.org

Paul Smith's Contact:

Kenneth Aaron

+1 (518) 327-6297

kaaron@paulsmiths.edu

WASHINGTON - A new study reveals correlations between

plentiful sunspots and periods of heavy rain in East Africa.

Intense rainfall in the region often leads to flooding and

disease outbreaks.

The analysis by a team of U.S. and British researchers shows that

unusually heavy rainfalls in East Africa over the past century

preceded peak sunspot activity by about one year. Because periods

of peak sunspot activity, known as solar maxima, are predictable,

so too are the associated heavy rains that precede them, the

researchers propose.

"With the help of these findings, we can now say when especially

rainy seasons are likely to occur, several years in advance," says

paleoclimatologist and study leader Curt Stager of Paul Smith's

College in Paul Smiths, New York. Forewarned by such predictions,

public health officials could ramp up prevention measures against

insect-borne diseases long before epidemics begin, he adds.

The sunspot-rainfall analysis is scheduled to appear on 7 August

in the Journal of Geophysical Research - Atmospheres, a publication

of the American Geophysical Union.

Increasing sunspot numbers indicate a rise in the sun's energy

output. Sunspot abundance peaks on an 11-year cycle. The next solar

maximum is expected in 2011-2012. If the newfound pattern holds, rainfall

would also peak the year before.

"We expect East Africa to experience a major intensification of

rainy season precipitation, along with widespread Rift Valley Fever

epidemics, a year or so before the solar maximum of 2011-2012," the

team reports. Because mosquitoes and other disease-carrying insects

thrive in wet conditions, heavy rains may herald outbreaks of

diseases such as Rift Valley Fever.

The new analysis relies on rainfall data going back a century. The

scientists also used historical records of water levels at lakes

Victoria, Tanganyika, and Naivasha.

The work counters previous research that found no connection

between sunspot cycles and rainfall in East Africa. Stager's team

concludes that, although the link between sunspots and rainfall was

weak between 1927 and 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 El Nino and

other climatic disturbances not associated with sunspots.

Scientists have investigated apparent correlations between solar

variability and Lake Victoria's water levels since the beginning of

the last century, says co-author Alexander Ruzmaikin of NASA's Jet

Propulsion Laboratory in Pasadena, California. The new research

"shows that these correlations are, in fact, not accidental,

effectively resolving a longstanding historical puzzle and improving

our knowledge of how solar variability affects Africa's climate," he

adds.

Stager, Ruzmaikin and their colleagues offer several reasons why

sunspot peaks may affect rainfall. In a simple scenario, increased

solar energy associated with sunspots heats both land and sea, forcing

moist air to rise and triggering precipitation.

While sunspot peaks augur extraordinarily wet rainy seasons, heavy

rains are possible at other times as well, Stager acknowledges. But,

most of the rainiest times, he says, are consistently coupled with the

predictable rhythms of sunspot peaks. And, to be forewarned is to be

forearmed.

"The hope is that people on the ground will use this research to predict

heavy rainfall events," Stager says. "Those events lead to erosion,

flooding, and disease."

The National Science Foundation funded the study.

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Notes for Journalists

Journalists and public information officers of educational and

scientific institutions (only) can receive a PDF copy of this paper by

sending a message to Jonathan Lifland at jlifland@agu.org. Please

provide your name, the name of your publication, and your phone number.

Members of the public can read the abstract of any published paper by

clicking on the link in the citation below. The full scientific article

is available for purchase through a link in the abstract.

Neither the paper nor this press release are under embargo.

Title:

"Sunspots, El Nino, and the levels of Lake Victoria, East Africa"

Authors:

J. Curt Stager, Natural Sciences Division, Paul Smith's College, Paul

Smiths, NY 12970, USA;

Alexander Ruzmaikin, Jet Propulsion Laboratory, California Institute

of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA;

Declan Conway, School of Development Studies, University of East

Anglia, Norwich NR4 7TJ, UK;

Piet Verburg, Institute of Ecology, University of Georgia, Athens, GA

30602, USA;

Peter J. Mason, MWH UK Ltd, Terriers House, 201 Amersham Road,

High Wycombe, Bucks HP13 5AJ, UK.

Citation:

Stager, J. C., A. Ruzmaikin, D. Conway, P. Verburg, and P. J. Mason

(2007), Sunspots, El Nino, and the levels of Lake Victoria, East

Africa, J. Geophys. Res., 112, D15106, doi:10.1029/2006JD008362.

Contact information for authors:

Curt Stager, professor of natural resources, office phone: +1

(518) 327-6342, cstager@paulsmiths.edu