The wrath of 2007: America's great drought

America is facing its worst summer drought since the Dust Bowl years of the Great Depression. Or perhaps worse still. From the mountains and desert of the West, now into an eighth consecutive dry year, to the wheat farms of Alabama, where crops are failing because of rainfall levels 12 inches lower than usual, to the vast soupy expanse of Lake Okeechobee in southern Florida, which has become so dry it actually caught fire a couple of weeks ago, a continent is crying out for water. In the south-east, usually a lush, humid region, it is the driest few months since records began in 1895. California and Nevada, where burgeoning population centres co-exist with an often harsh, barren landscape, have seen less rain over the past year than at any time since 1924. The Sierra Nevada range, which straddles the two states, received only 27 per cent of its usual snowfall in winter, with immediate knock-on effects on water supplies for the populations of Las Vegas and Los Angeles...But the long-term implications are escaping nobody. Climatologists see a growing volatility in the south-east's weather - today's drought coming close on the heels of devastating hurricanes two to three years ago. In the West, meanwhile, a growing body of scientific evidence suggests a movement towards a state of perpetual drought by the middle of this century. "The 1930s drought lasted less than a decade. This is something that could remain for 100 years," said Richard Seager a climatologist at Columbia University and lead researcher of a report published recently by the government's National Oceanic and Atmospheric Administration (NOAA). While some of this year's dry weather is cyclical - California actually had an unusually wet year last year, so many of the state's farmers still have plenty of water for their crops - some of it portends more permanent changes. In Arizona, the tall mountains in the southern Sonoran desert known as "sky islands" because they have been welcome refuges from the desert heat for millennia, have already shown unmistakable signs of change....