Dec 11, 2009

A 1,200-year perspective of 21st century drought in southwestern North America

by
Connie A. Woodhouse, David M. Meko, Glen M. MacDonald, Dave W. Stahle, Edward R. Cook
,
Proceedings of the National Academy of Sciences
  • States a key feature of anticipated 21st century droughts in Southwest North America is the concurrence of elevated temperatures and increased aridity
  • Assesses instrumental records and paleoclimatic evidence for past prolonged drought in the Southwest that coincide with elevated temperatures to provide insights on temperature-drought relations and to develop worst-case scenarios for the future
  • Looks at, in particular, the medieval period from ~AD 900-1300 when the Northern Hemisphere experienced temperatures warmer than all but the most recent decades, finding that:
    • Paleoclimatic and model data indicate increased temperatures in western North America of approximately 1 °C over the long-term mean
    • This was a period of extensive and persistent aridity over western North America
    • Paleoclimatic evidence suggests drought in the mid-12th century far exceeded the severity, duration, and extent of subsequent droughts
    • The driest decade of this drought was anomalously warm, though not as warm as the late 20th and early 21st centuries
  • Holds that the mid-12th century may serve as a conservative analogue for severe droughts that might occur in the future due to the convergence of prolonged warming and arid conditions
  • Concludes that the causes of past and future drought will not be identical but warm droughts, inferred from paleoclimatic records, demonstrate the plausibility of extensive, severe droughts, provide a long-term perspective on the ongoing drought conditions in the Southwest, and suggest the need for regional sustainability planning for the future