But if you look at the [Medieval] warm centuries with a global perspective, the wide incidence of drought is truly striking and offers a sobering message about tomorrow's world. Prolonged aridity was widepread in medieval times and killed enormous numbers of peope. Evidence is mounting that drought is the silent and insidious killer associated with global warming. The casualty figures are mind numbing. About 11 million people between Kenya, Somalia, Ethiopia, and Eritrea were in serious danger of starvation as a result of multiyear droughts in 2006. The International Institute of Tropical Agriculture in Nigeria estimates that by 2010 around 300 million people in sub-Saharan Africa, nearly a third of the population, will suffer from malnutrition because of intensifying drought ...-- Brian Fagan, The Great Warming: Climate Change and the Rise and Fall of Civilizations
The long-term future is even more alarming. A study by Britain's authoritative Hadley Center for Climate Change documents a 25 percent increase in global drought during the 1990s, which produced well documented population losses. The Hadley's computer models of future aridity resulting from the impacts of greenhouse gas emissions are truly frightening. At present, extreme drought affects 3 percent of the earth's surface. The figure could rise as high as 30 percent if warming continues, with 40 percent suffering from severe droughts, up from the current figure of 8 percent. Fifty percent of the world's land would expereince moderate drought, up from the present of 25 percent. Then the center ran the model without factoring in the impact of greenhouse gases, which they assumed were the temperature change villans. The results implied that future changes in drought without anthropogenic warming would be very small indeed.
In human terms, the United Nations Environment Program reports that 450 million people in twenty-nine countries currently suffer from water shortages. By 2025, an estimated 2.8 billion of us will live in areas with increasingly scarce water resources.
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