[ d r o u g h t s   :   p r e d i c t i o n ]

Scientists have been able to tell when droughts have occurred in the past by dendrochronology, the science of studying tree rings. The rings represent the amount of growth each tree has undergone in a given year. Wide rings usually mean that the tree grew a lot in that year, while thin rings indicate there was little nutrition and less growth. Usually, thin rings occur at the same time as droughts, when little water is available. From looking at ancient trees and fossilized remains, scientists can tell that the southwestern United States experienced a serious drought, lasting twenty-six years, 2,000 years ago. Recently, scientists have discovered that droughts occur in cycles of every twenty-two years. In other countries, such as China, they appear once every ten years. Researchers think that such cyclic patterns are caused by sunspots, dark, cool areas on the surface of the sun. Sunspots also appear every twenty-two years, growing larger and fading in that period of time. Related to sunspots are hot particles that shoot out from the sun and hit the earth’s atmosphere, heating it up. Although they do not make that great a change in air temperature, it may be enough to cause the slight changes that increase the probability of drought. If this theory is correct, then it will be easier to predict droughts in the future. However, no substantial proof has been found of a distinct correlation between the two. It is also possible to predict droughts from weather forecasts, by examining areas of high-pressure and looking at global climate patterns.

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