The historical climate record for Africa shows warming of approximately 0.7°C over most of the continent during the 20th century, a decrease in rainfall over large portions of the Sahel, and an increase in rainfall in east central Africa. Climate change scenarios for Africa, based on results from several general circulation models using data collated by the Intergovernmental Panel on Climate Change (IPCC) Data Distribution Center (DDC), indicate future warming across Africa ranging from 0.2°C per decade (low scenario) to more than 0.5°C per decade (high scenario). This warming is greatest over the interior of semi-arid margins of the Sahara and central southern Africa.
Projected future changes in mean seasonal rainfall in Africa are less well defined. Under the low-warming scenario, few areas show trends that significantly exceed natural 30-year variability. Under intermediate warming scenarios, most models project that by 2050 north Africa and the interior of southern Africa will experience decreases during the growing season that exceed one standard deviation of natural variability; in parts of equatorial east Africa, rainfall is predicted to increase in December-February and decrease in June-August. With a more rapid global warming scenario, large areas of Africa would experience changes in December-February or June-August rainfall that significantly exceed natural variability.
Water: Africa is the continent with the lowest conversion factor of precipitation to runoff, averaging 15%. Although the equatorial region and coastal areas of eastern and southern Africa are humid, the rest of the continent is dry subhumid to arid. The dominant impact of global warming is predicted to be a reduction in soil moisture in subhumid zones and a reduction in runoff. Current trends in major river basins indicate a decrease in runoff of about 17% over the past decade. Reservoir storage shows marked sensitivity to variations in runoff and periods of drought. Lake storage and major dams have reached critically low levels, threatening industrial activity. Model results indicate that global warming will increase the frequency of such low storage episodes.
Natural Resources Management and Biodiversity: Land-use changes as a result of population and development pressures will continue to be the major driver of land-cover change in Africa, with climate change becoming an increasingly important contributing factor by mid-century. Resultant changes in ecosystems will affect the distribution and productivity of plant and animal species, water supply, fuelwood, and other services. Losses of biodiversity are likely to be accelerated by climate change, such as in the Afromontane and Cape centers of plant endemism. Projected climate change is expected to lead to altered frequency, intensity, and extent of vegetation fires, with potential feedback effects on climate change.
Human Health: Human health is predicted to be adversely affected by projected climate change. Temperature rises will extend the habitats of vectors of diseases such as malaria. Droughts and flooding, where sanitary infrastucture is inadequate, will result in increased frequency of epidemics and enteric diseases. More frequent outbreaks of Rift Valley fever could result from increased rainfall. Increased temperatures of coastal waters could aggrevate cholera epidemics in coastal areas.
Food Security: There is wide consensus that climate change, through increased extremes, will worsen food security in Africa. The continent already experiences a major deficit in food production in many areas, and potential declines in soil moisture will be an added burden. Food-importing countries are at greater risk of adverse climate change, and impacts could have as much to do with changes in world markets as with changes in local and regional resources and national agricultural economy. As a result of water stress, inland fisheries will be rendered more vulnerable because of episodic drought and habitat destruction. Ocean warming also will modify ocean currents, with possible impacts on coastal marine fisheries.
Settlements and Infrastructure: The basic infrastructure for developmenttransport,
housing, servicesis inadequate now, yet it represents substantial investment
by governments. An increase in damaging floods, dust storms, and other extremes
would result in damage to settlements and infrastructure and affect human health.
Most of Africa's largest cities are along coasts. A large percentage of Africa's population is land-locked; thus, coastal facilities are economically significant. Sea-level rise, coastal erosion, saltwater intrusion, and flooding will have significant impacts on African communities and economies.
Desertification: Climate change and desertification remain inextricably linked through feedbacks between land degradation and precipitation. Climate change might exacerbate desertification through alteration of spatial and temporal patterns in temperature, rainfall, solar insolation, and winds. Conversely, desertification aggravates carbon dioxide (CO2)-induced climate change through the release of CO2 from cleared and dead vegetation and reduction of the carbon sequestration potential of desertified land. Although the relative importance of climatic and anthropogenic factors in causing desertification remains unresolved, evidence shows that certain arid, semi-arid, and dry subhumid areas have experienced declines in rainfall, resulting in decreases in soil fertility and agricultural, livestock, forest, and rangeland production. Ultimately, these adverse impacts lead to socioeconomic and political instability. Potential increases in the frequency and severity of drought are likely to exacerbate desertification.
Given the range and magnitude of the development constraints and challenges facing most African nations, the overall capacity for Africa to adapt to climate change is low. Although there is uncertainty in what the future holds, Africa must start planning now to adapt to climate change. National environmental action plans and implementation must incorporate long-term changes and pursue "no regret" strategies. Current technologies and approachesespecially in agriculture and waterare unlikely to be adequate to meet projected demands, and increased climate variability will be an additional stress. Seasonal forecastingfor example, linking sea-surface temperatures to outbreaks of major diseasesis a promising adaptive strategy that will help save lives. It is unlikely that African countries on their own will have sufficient resources to respond effectively.
Climate change also offers some opportunities. The process of adapting to global climate change, including technology transfer, offers new development pathways that could take advantage of Africa's resources and human potential. Examples would include competitive agricultural products, as a result of research in new crop varieties and increased international trade, and industrial developments such as solar energy. Regional cooperation in science, resource management, and development already are increasing.
This assessment of vulnerability to climate change is marked by uncertainty. The diversity of African climates, high rainfall variability, and a very sparse observational network make predictions of future climate change difficult at the subregional and local levels. Underlying exposure and vulnerability to climatic changes are well established. Sensitivity to climatic variations is established but incomplete. However, uncertainty over future conditions means that there is low confidence in projected costs of climate change.
Improvements in national and regional data and capacity to predict impacts is essential. Developing African capacity in environmental assessment will increase the effectiveness of aid. Regional assessments of vulnerability, impacts, and adaptation should be pursued to fill in the many gaps in information.
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