Environment Counts | Assessment of the droughts of the 20th century compared to droughts for the past 300 years
Author: Geoff Zeiss – Published At: 2011-07-19 00:41 – (831 Reads)
Droughts of the last four centuries are well documented in paleoclimatic proxies such as historical documents and tree rings. Spatial patterns of drought for every year since 1700 have been generated from a gridded network of tree-ring reconstructions. Highlighted are those periods with droughts that appear to have been more severe than any we have experienced in the 20th century.
Longer records show strong evidence for a drought that appears to have been more severe in some areas of central North America than anything we have experienced in the 20th century, including the 1930s drought. Tree-ring records from around North America document episodes of severe drought during the last half of the 16th century. Drought is reconstructed as far east as Jamestown, Virginia, where tree rings reflect several extended periods of drought that coincided with the disappearance of the Roanoke Colonists, and difficult times for the Jamestown colony. These droughts were extremely severe and lasted for three to six years, a long time for such severe drought conditions to persist in this region of North America.
Coincident droughts, or the same droughts, are apparent in tree-ring records from Mexico to British Columbia, and from California to the East Coast (See examples in the graph to the right). Winter and spring drought conditions appear to have been particularly severe in the Southwestern U.S. and northwestern Mexico, where this drought appears to have lasted several decades. In other areas, drought conditions were milder, suggesting drought impacts may have been tempered by seasonal variations.