NASA Data Show Some African Drought Linked to Warmer Indian Ocean

GREENBELT, Md., Aug. 5 /PRNewswire-USNewswire/ -- A new study, co-funded by
NASA, has identified a link between a warming Indian Ocean and less rainfall
in eastern and southern Africa. Computer models and observations show a
decline in rainfall, with implications for the region's food security.

Rainfall in eastern Africa during the rainy season, which runs from March
through May, has declined about 15 percent since the 1980s, according to
records from ground stations and satellites. Statistical analyses show that
this decline is due to irregularities in the transport of moisture between the
ocean and land, brought about by rising Indian Ocean temperatures, according
to research published today in Proceedings of the National Academy of
Sciences. This interdisciplinary study was organized to support U.S. Agency
for International Development's Famine Early Warning Systems Network.

"The last 10 to 15 years have seen particularly dangerous declines in rainfall
in sensitive ecosystems in East Africa, such as Somalia and eastern Ethiopia,"
said Molly Brown of NASA's Goddard Space Flight Center, Greenbelt, Md., a
co-author of the study. "We wanted to know if the trend would continue or if
it would start getting wetter."

To find out, the team analyzed historical seasonal rainfall data over the
Indian Ocean and the eastern seaboard of Africa from 1950 to 2005. The NASA
Global Precipitation Climatology Project's rainfall dataset provided a series
of data covering both the land and the oceans. They found that declines in
rainfall in Ethiopia, Kenya, Tanzania, Zambia, Malawi and Zimbabwe were linked
to increases in rainfall over the ocean.

The team used computer models that describe the atmosphere and historical
climate data to identify and validate the source of this link. Lead author
Chris Funk of the University of California, Santa Barbara, and colleagues
showed that the movement of moisture onshore was disrupted by increased
rainfall over the ocean.

Funk and colleagues used a computer model from the National Center for
Atmospheric Research to confirm their findings. The combination of evidence
from models and historical data strongly suggest that human-caused warming of
the Indian Ocean leads to an increase of rainfall over the ocean, which in
turn adds energy to the atmosphere. Models showed that indeed, the added
energy could create a weather pattern that reduces the flow of moisture
onshore and bring dry air down over the African continent, reducing rainfall.

Next, the team investigated whether or not the decline in rainfall over
eastern Africa would continue. Under guidance from researchers at USGS, which
co-funded the study, the team looked at 11 climate models to simulate rainfall
changes in the future. Ten of the 11 models agreed that through 2050, rainfall
over the Indian Ocean would continue to increase - depriving Africa's eastern
seaboard of rainfall.

"We can be quite certain that the decline in rainfall has been substantial and
will continue to be," Funk said. "This 15 percent decrease every 20-25 years
is likely to continue."

The trend toward dryer rainy seasons in eastern and southern Africa directly
impacts agricultural productivity. To evaluate how potential future rainfall
scenarios and shifts in agriculture could affect undernourishment, the team
came up with a "food-balance indicator" model. The model considers factors
such as growing-season rainfall, fertilizer, seed use, crop area and
population to estimate the number of undernourished people a region can
anticipate.

Continuing along a "business as usual" scenario - with current trends in
declining rainfall and agricultural capacity continuing as it is currently to
2030, the team found that the number of undernourished people will increase by
more than 50 percent in eastern Africa.

Still, the food-balance indicator also showed that in the face of a
continuation of the current downward trend in rainfall, even modest increases
in agricultural capacity could reduce the number of undernourished people by
40 percent.

"A strong commitment to agricultural development by both African nations and
the international community could lead fairly quickly to a more food-secure
Africa," Funk said.

For information about NASA and agency programs, visit:

http://www.nasa.gov/home

SOURCE NASA

Lynn Chandler of NASA Goddard Space Flight Center, Md., +1-301-286-2806,
lynn.chandler-1@nasa.gov