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摘要

When the worst drought in 60 years hit America's corn belt this summer, many people wondered if it was caused by climate change. It is too early to say much about such a recent episode but various studies have attributed earlier individual heatwaves or drought to global warming, notably those in Europe in 2003, Russia in 2010 and the sweltering summer of 2011 in Texas. The most recent (2007) assessment by the Intergovernmental Panel on Climate Change (ipcc) said bluntly: "higher temperatures and decreased precipitation have contributed to changes in drought." This week a study for the World Bank by the Potsdam Institute for Climate Impact Research argued that "extreme summer temperatures can now largely be attributed to climatic warming since the 1960s."