An opinion piece in the Sunday, August 12, 2012 New York Times by three scientists (listed at the end) deserves repeating. Here are some excerpts:
Until recently, many scientists spoke of climate change mainly as a “threat,” sometime in the future. But it 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.
In terms of severity and geographic extent, the 2000-4 drought in the West exceeded such legendary events as the Dust Bowl of the 1930s. More seriously still, long-term climate records from tree-ring chronologies show that this drought was the most severe event of its kind in the western United States in the past 800 years.
Most frightening is that this extreme event could become the new normal: climate models point to a warmer planet, largely because of greenhouse gas emissions. Planetary warming, in turn, is expected to create drier conditions across western North America, because of the way global-wind and atmospheric-pressure patterns shift in response.
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.
And yet that may be only the beginning, a fact that should force us to confront the likelihood of new and painful challenges. A megadrought would present a major risk to water resources in the American West, which are distributed through a complex series of local, state and regional water-sharing agreements and laws. Virtually every drop of water flowing in the American West is legally claimed, sometimes by several users, and the demand is expected to increase as the population grows.
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.
(Christopher R. Schwalm is a research assistant professor of earth sciences at Northern Arizona University. Christopher A. Williams is an assistant professor of geography at Clark University. Kevin Schaefer is a research scientist at the National Snow and Ice Data Center)
Courtesy Mark Svoboda, National Drought Mitigation Center.