Climate change effects on the water supply in some major river basins
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2005 by Taylor & Francis Group, LLC. While the Green Revolution during the latter part of the 20th century may have been facilitated by higher-yield grain varieties, the impact of increased water harvesting techniques (dams, irrigation systems) on agricultural production cannot be ignored. The promotion of agriculture to sequester carbon will require the careful evaluation of future water availability. The following are widely thought to impact the water cycle in a future climate: (1) greenhouse gases (GHGs) such as CO2, CH4, and N2O, are expected to increase from human related activities such as fuel emission and fertilizer application; (2) air and sea surface temperatures (SST) will rise due to GHGs; (3) the number of extreme events (flooding, drought, tornados due to SST-related El Nio/Southern Oscillation [ENSO] events) precipitation intensity may increase, that is, the wet periods will get wetter and the dry periods will get drier; (4) the quality of arable land may decline due to increased salinization, erosion, and poor management; and (5) urban population growth will continue at or above current rates. Iraq serves as an example of point 4. While about 3.5 million ha are potentially cultivable in irrigated agriculture, roughly half, 1.94 million ha, are actually cultivated due to water logging and salinization problems (Food and Agriculture Organization [FAO], 1997). Recent extreme events from the late 1990s to the present - such as the flooding of the Elbe in Central Europe in August 2002, the 1998 flooding of the Yangzte in China, the 2000 and 2002 droughts in monsoondependent India, and the highest recorded tornado activity in the United States in 2003 - are visible signs of potential trends in extreme events. During 2003, the World Meteorological Organization took the unprecedented step of announcing likely changes in extreme events in its reporting. Historical analysis has traced changes in civilization from changes in the Holocene climate (DeMenocal, 2001).