This appeared in The New York Times last Saturday. It’s written by three scientists: Christopher R. Schwalm, research assistant professor of earth sciences at Northern Arizona University; Christopher A. Williams, assistant professor of geography at Clark University, and Kevin Schaefer, research scientist at the National Snow and Ice Data Center.
[I]t is increasingly clear that we already live in the era of human-induced climate change, with a growing frequency of weather and climate extremes like heat waves, droughts, floods and fires … [L]ong-term climate records from tree-ring chronologies show that [the 2000-4] drought was the most severe event of its kind in the western United States in the past 800 years. Though there have been many extreme droughts over the last 1,200 years, only three other events have been of similar magnitude, all during periods of “megadroughts” … Most frightening is that this extreme event could become the new normal … These climate-model projections suggest that what we consider today to be an episode of severe drought might even be classified as a period of abnormal wetness by the end of the century and that a coming megadrought — a prolonged, multidecade period of significantly below-average precipitation — is possible and likely in the American West.
The current drought plaguing the country is worryingly consistent with these expectations. Although we do not attribute any single event to global warming, the severity of both the turn-of-the-century drought and the current one is consistent with simulations accounting for warming from increased greenhouse gases. The Northern Hemisphere has just recorded its 327th consecutive month in which the temperature exceeded the 20th-century average. This year had the fourth-warmest winter on record, with record-shattering high temperatures in March. And 2012 has already seen huge wildfires in Colorado and other Western states. More than 3,200 heat records were broken in June alone … Many Western cities will have to fundamentally change how they acquire and use water. The sort of temporary emergency steps that we grudgingly adopt during periods of low rainfall — fewer showers, lawn-watering bans — will become permanent. Some regions will become impossible to farm because of lack of irrigation water. Thermoelectric energy production will compete for limited water resources. There is still time to prevent the worst; the risk of a multidecade megadrought in the American West can be reduced if we reduce fossil-fuel emissions. But there can be little doubt that what was once thought to be a future threat is suddenly, catastrophically upon us.
Full story: “Hundred-Year Forecast: Drought,” The New York Times, August 11, 2012