Climate Science

Wetter or Drier?

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Science  16 May 2008:
Vol. 320, Issue 5878, pp. 850
DOI: 10.1126/science.320.5878.850a

One expected result of global climate warming is an overall increase in precipitation. Not every place will receive more rain—some will receive less, even though the average should increase. Certain changes are already apparent in various regions, such as a greater frequency of extreme rainfall events and a higher number of rainy days. Another potential change that could have important effects is an increase in prolonged dry spells. Groisman and Knight have compiled rainfall data covering the last 40 years from more than 4000 carefully selected stations across the conterminous United States, in order to determine if this pattern already has begun there. They find that it has. More precisely, they show that the mean duration of prolonged dry spells in the warm season has increased significantly, and that the return period of 1-month-long dry episodes over the eastern United States has decreased from 15 years to between 6 and 7 years. This pattern could be hazardous for terrestrial ecosystems and agriculture. — HJS

J. Climate 21, 1850 (2008).

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