Continental divide: why Africa's are change burden is greater

Environmental Health Perspectives, August, 2005 by Scott Fields

Africa can easily be said to contribute the least of any continent to global warming. Each year Africa produces an average of just over 1 metric ton of the greenhouse gas carbon dioxide per person, according to the U.S. Department of Energy's International Energy Annual 2002. The most industrialized African countries, such as South Africa, generate 8.44 metric tons per person, and the least developed countries, such as Mall, generate less than a tenth of a metric ton per person. By comparison, each American generates almost 16 metric tons per year. That adds up to the United States alone generating 5.7 billion metric tons of carbon dioxide per year (about 23% of the world total, making it the leading producer), while Africa as a whole contributes only 918.49 million metric tons (less than 4%). It is a cruel irony that, in many experts' opinion, the people living on the continent that has contributed the least to global warming are in line to be the hardest hit by the resulting climate changes.

"The critical challenge in terms of climate change in Africa is the way that multiple stressors--such as the spread of HIV/AIDS, the effects of economic globalization, the privatization of resources, and conflict--converge with climate change," says Siri Eriksen, a senior research fellow in sociology and human geography at the University of Oslo. "It is where several stressors reinforce each other that societies become vulnerable, and impacts of climate change can be particularly severe." She cites the example of the 2002 drought-triggered famine in southern Africa, which affected millions due partly to populations" coping capacity being weakened by HIV/AIDS.

"Climate change could undo even the little progress most African countries have achieved so fat in terms of development," says Anthony Nyong, a professor of environmental science at the University of Jos in Nigeria. With climate change has come an increase in health problems such as malaria, meningitis, and dengue fever, he says. This means that the few resources these poor countries have that would have been channeled into essential projects to further economic development must instead be put toward health crisis after health crisis, providing emergency care for the people.

Models of Change

Africa may already be feeling the effects of global warming, says Isaac Held, a senior research scientist at the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory, and more marked effects are likely to come, according to models developed by climate scientists around the world Projected effects of global warming on precipitation throughout the world can be summarized in a single sentence, according to Held: areas that already get a tot of rainfall--such as the equatorial and subpolar rain belts will get more, and areas that get little--such as the subtropical dry zones will get less.

Climate models suggest that subtropical Africa south of the equator will follow this trend, and a plausible case can be made that global warming has already reduced rainfall in that region. In a paper published in the September 2004 issue of the International Journal of Climatology, NOAA scientist Pingping Xie and colleagues wrote, "Large decreasing rainfall trends were widespread in the Sahel from the late 1950s to the late 1980s; thereafter, Sahel rainfall has recovered somewhat through 2003, even though the drought conditions have not ended in the region." The study also found that major multiyear oscillations have appeared to occur more frequently and to be more extreme since the late 1980s.

About 300,000 people died in a prolonged drought in the Sahel during the 1970s. Until recently the scientific community attributed that drought to the severe loss of vegetation accompanying such factors as overgrazing and overpopulation; according to this model, the reduction in vegetation meant greater reflectivity of the Earth's surface and less moisture being returned to the atmosphere, with a net drying effect. But now, Held says, "we think of that drought as having been driven by changes in the ocean temperatures."

New climate models posit that precipitation changes are occurring because of alterations in the temperature gradient between the Southern and Northern hemispheres. "When the [ocean] waters are warmer in the Northern Hemisphere, rains are attracted farther north, and when they are warmer in the Southern Hemisphere, it doesn't get as far north," Held explains.

But it is a subject of debate, he says, whether the changes in temperature gradient that caused the Sahel drought were due to natural variability of the oceans or were partly the result of man-made changes in the composition of the atmosphere. There is as yet no consensus among climate modelers on the most likely future trend of Sahel rainfall, he emphasizes.

Still, climatologists agree that warming is happening. In Climate Change 2001: Impacts, Adaptation and Vulnerability, the Intergovernmental Panel on Climate Change Working Group II reported, "The historical climate record for Africa shows warming of approximately 0.7[degrees]C [1.3[degrees]F] over most of the continent during the twentieth century; a decrease in rainfall over large portions of the Sahel ... and an increase in rainfall in east central Africa."