The data base focuses on drought variability in North America for the past 300 years. It combines data from weather instruments for the past 100 years with a network of drought records reconstructed from tree ring chronologies dating from 1700. These reconstructions also enable an assessment of the severity of 20th century droughts in the context of the past three centuries. For example, when the extreme 1950s drought is compared with other droughts in the past 300 years, reconstructions suggest that a drought that occurred around 1820 was similar in length, and perhaps greater in severity and spatial extent. The data base was created by scientists at NOAA's National Geophysical Data Center in Boulder, Colo., NOAA's National Climatic Data Center in Asheville, N.C., and researchers from the University of Arizona, the University of Arkansas, and the Lamont- Doherty Earth Observatory of Columbia University.
Plans call for adding additional centuries-long records and information.
The goal will be to expand the geographic coverage, sample density, and record lengths covered. In studying past climates that existed before instruments were invented, scientists use proxy data such as sediments, tree rings, lake level changes, archaeological data, and historical accounts.