Current Drought Could Get Much Worse

The National Oceanic and Atmospheric Administration sees some easing of drought conditions this winter. Continued global warming, however, may portend much longer and more serious dry spells, a team of scientists says.

The five-years-plus drought affecting western North America pales in comparison with a series of ?EUR??,,????'??megadroughts?EUR??,,????'?? that slammed the continent from AD 900 to 1300, a team of researchers reports in Science magazine this month.

Using tree-ring data, the scientists found that at least four droughts lasting decades, not years, ravaged North America around AD 936, 1034, 1150 and 1253. Together, the monumental dry spells coincide with the Medieval Warm Period, a time of elevated global temperatures already known to climatologists. Comparing the two, the authors of the paper conclude that elevated global temperatures led to the droughts and that contemporary warming could be a harbinger of much more serious and persistent droughts than residents have experienced so far.

?EUR??,,????'??Compared to the earlier 'megadroughts'?EUR??,,????'??? the current drought does not stand out as an extreme event, because it has not lasted nearly as long,?EUR??,,????'?? the authors write. ?EUR??,,????'??This finding shows that the West can experience far more severe droughts than any found in the 20th century?EUR??,,????'??? including the current one.?EUR??,,????'??

The climatologist authors do not speculate on the biological impact of these megadrought conditions, but do note a greater number of fire scars on California's giant sequoia trees during the 400-year drought period. Other data shows elevated levels of charcoal in lake bottom sediment during the same period.

Source: Science, Vol. 306, Nov. 5, 2004