Uncertainty in West African climate models addressed

May 28, 2002

Plans to meet the outcome of global climate change are underway worldwide, but nowhere is that planning more difficult than in West Africa where the climate has some of the largest signals of change and the climate models have the greatest level of uncertainty, according to Penn State meteorologists.

"Adaptability to change is important, but it is hard to determine what to do until we have good climate assessments and can model potential impacts," says Dr. Gregory S. Jenkins, assistant professor of meteorology. "We know the area is in a trend of less precipitation and higher temperatures, but we do not fully understand why."

Jenkins, working with A. T. Gaye, Cheikh Anta Diop University, Senegal, and A. J. Adedoyin, University of Botswana, Botswana, as part of a United Nations environmental program, is looking at the climate trends and at the global climate models. The climate in West Africa -- the area north of the equator and south of the Sahara desert from Chad in the east to Guinea and Senegal on the west -- has suffered repeated droughts since the 1960s. Recent studies show that the mean rainfall in the Sahel, the area south of the Sahara in West Africa, dropped 37 percent in the period from 1968 to 1997 compared to the period from 1930 to 1960. Temperatures in the region are also warming, with most increases in the spring, summer and autumn months.

"Trying to use observations to extrapolate to the future is not easy,"Jenkins told attendees today (May 28) at the spring meeting of the American Geophysical Union in Washington, D.C. "Rain occurs in West Africa in the hundred to thousand kilometer ranges, but this mesoscale range is too small for the global models. Storms are too small to be noticed by the global climate models."

The solution is to use nested models, regional climate models linked to the global climate models. To do this, the regional models must be tested against observations and then applied to climate change scenarios.

"Eventually, we want the results to go to the end user," says Jenkins. "The water resource planners, health planners and agriculturalists who can use the models to plan adaptations to change. These are people who need to know how the timing, patterns and amounts of rain have changed."

Jenkins hopes to begin to answer questions about what is happening to climate in West Africa. Researchers know that when rainfall decreases, the winds of the African Easterly Jet at 10,000 feet decrease in intensity and the winds of the Tropical Easterly Jet at 30,000 feet decrease as well. However, what is not known with climate change is if the rainy season gets shorter, or if less rain falls over the same period of time. Or does the season begin earlier and end later?

Questions like these are important not just for water and food security, but also for economic development because most power in the region comes from hydroelectric plants that depend on river flows.

"People in this area frequently lose power once or twice a week," says Jenkins. "Climate changes could seriously impact power supply."

A better understanding of the changes occurring in the region and the way it will alter life in West Africa will hopefully be the result of a better modeling of climate in the area. Before regional plans are formulated to meet future climate change and help the peoples of West Africa adapt to the changes, researchers must understand the dynamics in the region.

Penn State

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