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Using a combination of tree ring estimates of drought variably of the

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last thousands years along with the state of art climate models simulations

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of the next hundred years. We've been studying drought try to understand

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what affect global warming and climate change will have on drought

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in the western United States, over the next hundred years. If you

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think about the current on going droughts, such as the drought in California

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the drought in the southwest, the, even the historical dust bowl drought of the

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1930s. these are natural occurring droughts that lasted on the order of

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or will last on the order of several years and some cases even

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a decade. What our projections shows is that these, in the future we can

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expect droughts that will last 20, 30, 40 years, even exceeding

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the duration of the long term intense mega droughts that characterized

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the really arid time period known as the mid-evil climate anomaly

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These droughts are likely to have major implications and major stresses

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on water resource use in the United States. Because

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there longer droughts than really anybody has experienced in the entire history of the United States.

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An while much of the work are based on computer model simulations

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these computer models really represent the best, our best

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understanding of how the climate system works. They are tested very extensively

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against observations. An at the end of the day, they are the only tool we really have

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to investigate future climate change.

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We expect that these droughts are going to begin sometime in the middle of the 21st century.

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They are going to present potently a very large management challenge

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for agricultural, eco-systems and

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people in western north America.

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