Climate change in Africa
In the coming decades, billions of people, particularly those in developing countries, will face shortages of water and food and greater risks to health and life as a result of climate change. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC 2007a) dispelled many uncertainties about climate change. Warming of the climate system is now unequivocal, and mostly due to man-made emissions of greenhouse gases. Over the past century, atmospheric concentrations of carbon dioxide increased from a pre-industrial value of 278 parts per million to 379 parts per million in 2005, and the average global temperature rose by 0.74° C – the largest and fastest warming trend discerned in the history of the Earth. An increasing rate of warming has taken place particularly over the past 25 years. The IPCC Report's detailed projections for the 21st century show that global warming will continue to accelerate. The best estimates indicate that the Earth could warm by 3° C by 2100. Even if cou ntries reduce their greenhouse gas emissions, the Earth will continue to warm. Predictions by 2100 range from a minimum of 1.8° C to as much as 4° C rise in global average temperatures, resulting in serious effects; these include reduced crop yields in tropical areas leading to increased risk of hunger, spread of climate sensitive diseases such as malaria, and an increased risk of extinction of 20–30% of plant and animal species (IPCC 2007b).
Africa is already a continent under pressure from climate stresses and is highly vulnerable to the impacts of climate change. Many areas in Africa are recognized as having climates that are among the most variable in the world on seasonal and decadal time scales. Serious floods and droughts can occur in the same area within months of each other. These events can lead to famine and widespread disruption of socio-economic well-being. An estimated one-third of African people already live in drought-prone areas and 220 million are exposed to drought each year. Many factors contribute to and compound the impacts of current climate variability in Africa. These include poverty, weak institutions, limited infrastructure, lack of technology and information, low levels of primary education and health care, poor access to resources, and armed conflicts. The overexploitation of land and water resources, increases in population, desertification and land degradation pose additional threats (UNDP 2006).
Climate change forecasts for Africa predict that the continent's weather patterns will become more variable, and extreme weather events are expected to be more frequent and severe, with increasing risk to health and life (McMichael et al. 2006). This includes increasing risk of drought and flooding in new areas (Few et al. 2004), and inundation due to sea-level rise in the continent's coastal areas (Nicholls 2004). Within the next 50 years, the number of people facing water stress will increase dramatically (Arnell 2004).
Climate change will be an added stress to already threatened species and ecosystems in Africa, and is likely to trigger species migration and habitat reduction on an unprecedented scale. Up to 50% of Africa's total biodiversity presently is at risk due to land-use conversion for settlement and agriculture, deforestation, pollution, poaching, civil war, population growth, and the introduction of exotic species (Boko et al. 2007). Freshwater ecosystems, especially river systems, have experienced rapid degradation due to the past century of water resources development, and are particularly vulnerable to the added effects of climate change (Palmer et al. 2008; Pittock et al. 2008; Vorosmarty et al. 2010).