Young boys working in a newly cropped field in Africa.

USGS geographer Michael Marshall has been studying the effects of evaporative processes on land – water emitted into the atmosphere from the soil and from plants – in East Africa and in the Sahel belt that crosses north-central Africa. Using output from a land surface model, Marshall found substantial drying over much of the Sahel and East Africa during the growing seasons.

“The Sahel is getting drier, and the land process that buffers the decline in rainfall is breaking down under increased warming,” said Marshall, a postdoctoral scholar with the USGS Western Geographic Science Center based in Flagstaff, Ariz. Marshall studies evapotranspiration – the combined effects of water entering the atmosphere via evaporation from the soil or from a plant surface, as well as transpiration, in which plants open their stomata (pores) to take in carbon from the atmosphere for food.

Most research into the effect of evaporation on global climate change deals with the oceans, since they form more than 75 percent of the earth’s surface. But evaporative processes on land are also important, because these processes can more easily be influenced by human activity and because, in some places, they can have a local effect on climate. Evapotranspiration triggers convection – the movement of columns of air – and rainfall. In the Sahel, evapotranspiration and localized convection are especially important because of the distance from the ocean or other large water bodies.

Using remote sensing satellite data and surface reanalysis data, downscaled from global general-circulation models, Marshall and his team analyzed evaporation in Africa over a 31-year period. In contrast to many Intergovernmental Panel on Climate Change (IPCC) simulations, which predict increased moisture over the Sahel, they identified substantial drying over much of the Sahel during the growing season, particularly in the last 10 to 12 years. To explain the discrepancy, Marshall suggested that the negative impacts of warming temperatures may be overcoming any possible rainfall recovery across the Sahel. He hypothesized that lands converted from natural vegetation to agriculture might have contributed to the change.

A herder moves cattle through a barren landscape in eastern Africa.

“The climate models for Africa tend to be uncertain in general, due to a lack of station data in Africa and the complexity of climate in the tropics. There is still much to be learned,” Marshall said.

Marshall suggested that the new agricultural crops, which have smaller root systems and are in the ground for a shorter time than the native perennials, may be so stressed by their harsh conditions that they are releasing less water into the atmosphere and thus affecting the climate. Very few African farmers have access to irrigation. Thus, any disruption of the process that creates convection and rainfall would greatly affect them in the long term.

Marshall aims in further research to use higher-resolution data to compare satellite and ground information from Africa with data from the central United States and from India, where the movement of air produced by evapotranspiration can also induce rainfall.  He hopes his work will give land managers tools to better understand these regions.

Marshall’s research supports the Famine Early Warning Systems Network (FEWS NET), which helps target more than $1.5 billion of food-related assistance to more than 40 countries each year. The USGS is actively involved in FEWS NET, which is sponsored by the U.S. Agency for International Development (USAID) Office of Food for Peace. FEWS NET examines the populations of the developing world with the most food insecurity, identifying critical situations in which food aid will be needed. Often the populations most in need are those whose livelihoods are tied to subsistence rain-fed agriculture and pastoralism.

Marshall’s findings, published in a recent issue of Climate Dynamics, are available online.

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Top Story: Science Helping to Save Lives in Africa

Top Pick: Poor Spring Rain Predicted in Africa

Young boys working in a newly cropped field in Africa.

Spring rains in the eastern Horn of Africa are projected to begin late this year and be substantially lower than normal.

From March–May, the rains are expected to total only 60 to 85 percentage of the average rainfall in this region. This is a significant deterioration compared to earlier forecasts.

Lower rain amounts would have significant impacts on crop production, rangeland regeneration for livestock, and replenishment of water resources.

This would put greater stress on the region, particularly Somalia which is still recovering from a famine declared last year, as well as Kenya and Ethiopia which also experienced a severe food crisis. An increase in food insecurity and in the size of the food insecure population is likely.

The State Department released a statement on this forecast and their intent to provide additional funding to aid refuges and drought-affected communities.

Famine Early Warning Systems Network

 The rainfall projections were completed by the Famine Early Warning Systems Network (FEWS NET), which helps target more than $1.5 billion of assistance to more than 40 countries each year. FEWS NET monitors high risk areas of the developing world with the most food insecurity, identifying critical situations in which food aid will be needed.

FEWS NET is sponsored and led by the U.S. Agency for International Development (USAID) Office of Food for Peace. Implementing partners include the U.S. Geological Survey (USGS), Chemonics International, Inc., National Aeronautics and Space Administration (NASA), National Oceanographic and Atmospheric Administration (NOAA), and the U.S. Department of Agriculture (USDA).

USGS Science

A herder moves cattle through a barren landscape in eastern Africa.

The USGS led the climate analysis for the recent FEWS NET rainfall projection.

“Rainfall projections were estimated by looking very closely at all the prior droughts from March–May since 1979 in the eastern Horn of Africa,” said USGS scientist Chris Funk, who led this research. “We found that sea surface temperatures in the western/central Pacific and the Indian oceans are key drivers of rainfall during that time period. So we compared sea surface temperatures from past years to March 2012, and developed an updated rainfall forecast for this spring season.”

Climate modeling analysis was done in collaboration with others, including Greg Husak and Joel Michaelsen with the Climate Hazards Group at the University of California, Santa Barbara, as well as Bradfield Lyon at The International Research Institute for Climate and Society. Lyon’s research identified the important role of the Pacific Ocean in recent droughts.

The USGS also contributes satellite remote sensing data and analysis of vegetation and rainfall to support FEWS NET activities throughout the world. Remote sensing from space allows scientists to provide rapid, accurate assessments of a broad range of environmental and agricultural conditions. A newly completed vegetation monitoring system allows FEWS NET analysts to track conditions across all of Africa in tremendous detail.

“The concerning picture that emerged from FEWS NET climate monitoring services was that despite the good rains of the past winter, the situation east Africa has deteriorated very rapidly, to a point that the water deficits and vegetation health looked as bad as this time last year,” said Funk.

Link between Sea Surface Temperatures and Rainfall

 As the globe has warmed over the last century, the Indian and central/western Pacific oceans have warmed particularly fast. USGS scientists found that the warming of these oceans affects rainfall over large areas of the Horn of Africa.

The resulting warmer air and increased humidity over the Indian and Pacific oceans produce more frequent rainfall over the oceans. The air then rises over the equatorial Indian and Pacific oceans, and flows westward, descending over Africa. Since the air has already lost moisture from rainfall over the oceans, this leads to decreased rain amounts in parts of eastern Africa. Trends toward increased frequency of drought that we are seeing now appear likely to continue into the future as warming continues.

“Essentially, our research has progressed to the point where we can recognize fairly well the climate patterns linked to the recent droughts, and we hope this helps identify potential bad seasons in advance to raise awareness,” said Funk.

More Information

Learn more about USGS science helping to save lives in Africa.

Listen to a podcast interview on FEWS NET and USGS research in Africa.

Young boys working in a newly cropped field in Africa.

In parts of eastern Africa, drought is of increasing concern, as poor families suffer from food shortages and the inability to grow crops and sustain livestock. Stunted growth in children due to malnutrition has also been linked to climate trends in Africa.

Drought conditions are expected to continue as global temperatures continue to rise and rainfall declines across parts of eastern Africa.

This poses increased risk to millions of people in Africa who currently face potential food shortages.

What’s being done to help?

The USGS is involved in a variety of research efforts to help understand current and future conditions in Africa, helping to inform plans to provide aid.

The Famine Early Warning Systems Network, or FEWS NET, is one endeavor that has already made great strides in helping to address this issue. FEWS NET helps target more than $1.5 billion of assistance to more than 40 countries each year.

FEWS NET examines the populations of the developing world with the most food insecurity, identifying critical situations in which food aid will be needed. These are populations whose livelihoods are typically tied to subsistence rain-fed agriculture and pastoralism.

FEWS NET is sponsored by the U.S. Agency for International Development (USAID) Office of Food for Peace and the USGS is actively involved.

FEWS NET at the United Nations Climate Convention

A USGS presentation on FEWS NET will be a featured side event on November 30, 2011, at the United Nations 17^th annual Conference of the Parties (COP-17) in Durban, South Africa. The convention’s purpose is to develop international agreements and a declaration of policies and practices for combating climate change and its impacts around the world.

A herder moves cattle through a barren landscape in eastern Africa.

Climate forecasts and remote sensing help spot future trouble

FEWS NET has developed its own climate services to provide decision makers with early identification of agricultural drought that might trigger food insecurity. Scientists use climate forecasts to develop forward-looking food security assessments that are based on expected agricultural outcomes for the season ahead.

Since networks of ground observation stations are often sparse or reported late in FEWS NET countries, satellite remote sensing of vegetation and rainfall fills in the gaps. Remote sensing from space allows for rapid, accurate assessments of a broad range of environmental and agricultural conditions. USGS scientists provide the technologies and expertise to support remote sensing for FEWS NET activities.

Early warning of famine in Somalia helps pre-position food supplies

On July 20, 2011, the United Nations declared parts of Somalia as a region of famine. The decision was supported by FEWS NET and USGS observational evidence of conditions in the area.

The declaration was the culmination of early warning communications encouraging — months before the crisis — that government and other agencies pre-position food and supplies in the region.

“None of the many uses of Earth-observing satellites is more vital — or has as much potential for prompting timely humanitarian intervention — as famine early warning,” said USGS Director Marcia McNutt. “Remote sensing from space allows USGS scientists to provide rapid, accurate assessments of a broad range of environmental and agricultural conditions.”

The eastern Horn of Africa, the continental region that encompasses Somalia, has experienced two consecutive seasons of very poor rainfall resulting in the worst drought in 60 years. Crops have failed, livestock deaths are widespread, and food prices are very high. While the rains this winter have been good, food prices remain high, and the food security situation remains insecure.

Stunted growth linked to malnutrition and climate change

Other USGS research is helping to identify the impacts of a changing climate on Africa’s people. Scientists recently discovered that malnutrition and dry hot living conditions are linked to stunted growth in Mali, West Africa.

USGS research found that Mali was becoming substantially warmer and a little bit drier. Scientists also knew that farmers and those who make a living raising sheep, cattle, goats, or camels were poor, and that stunted growth was occurring throughout Mali.

Scientists wondered if there could be a link between human health and increasingly warm and dry conditions.

To investigate, the USGS worked with the University of California, Santa Barbara, to study climate observations and demographic and health data. The Demographic and Health Survey program routinely compiles data from surveys in 90 countries to study trends in health and population. Scientists analyzed statistics on specific villages in Mali and found that there was a link between a warmer climate and increased stunting.

Population growth combined with the impacts of warming will further increase these health impacts.

Stunting was also linked to other factors, such as mother’s education and the water supply system. Women’s education, improved water supplies, and agricultural development could help to address malnutrition and stunting in Mali.

An article on this research was published in in the journal, Applied Geography, by San Diego State University, the University of California, Santa Barbara, and the USGS.

A Food Security Assessment in Somalia found severe impacts on livestock due to drought conditions.

Other studies underway

Other new research includes the discovery that the warming of the Indian and western Pacific oceans (which is linked to global warming) affects rainfall over large areas of the Horn of Africa. As the globe has warmed over the last century, the Indian Ocean and western Pacific have warmed especially fast.

The resulting warmer air and increased humidity over the Indian and western Pacific oceans produce more frequent rainfall in that region. The air loses its moisture during rainfall, and then flows westward and descends over Africa, leading to decreased rain in parts of eastern Africa. Trends toward increased frequency of drought that we are seeing now are likely to continue into the future as warming continues.

A few recent articles on this research were published in the journal, Climate Dynamics, by scientists with the USGS, the University of California, Santa Barbara, and Los Alamos National Laboratory. The most recent article concludes that global warming will lead to a decrease in rainfall during the summer monsoon season, from June to September, across southern Sudan, southern Ethiopia, and northern Uganda.  Another article concluded that eastern Africa, particularly Kenya and southern Ethiopia, will also have a significant decrease in rainfall during the long-rains season from March to June.

USGS scientists are working hard to translate these technical studies into reports for decision makers. To date, they have completed summary fact sheets focused on Sudan and Kenya.

Scientists also found that some regions, like northern Ethiopia, are not getting drier due to current warming temperatures. Rainfall varies dramatically across all of eastern Africa, with high mountainous areas typically receiving many times the rainfall received in low-lying areas. Therefore, agricultural growth in these climatically safe regions could help offset rainfall declines in other locations.

Start with science

Scientists are looking at clues and changes in nature to understand the impacts of global warming. In Africa, impacts are seen across the landscape — on farms and even in humans.

By starting with science, well-informed decisions can be made to help Africa as it faces drought, famine, and health concerns.

FEWS NET partners include the USAID, Chemonics International, the USGS, NASA, NOAA, and the USDA. The Geography Department at the University of California, Santa Barbara, is a partner to the USGS in this effort.

Want more information?

Listen to a podcast interview with USGS scientists as they discuss ongoing efforts to understand conditions in Africa.