Droughts, periods of below-normal precipitation, are a naturally occurring phenomenon in most areas of the
world.

Droughts may be short in duration-- such as an agricultural drought that lasts only a few months but nevertheless devastates crops-- or they may be severe hydrologic droughts that go on for a decade or longer, as in the case of the "mega-drought" in American Southwest during the 16th Century.

Because instrumented records are limited to primarily the past 100-150 years, paleoclimate records are crucial to gaining a long-term perspective on drought variability, particularly when it comes to multi-decadal droughts that have occurred prior to the instrumented records. Such an expanded view provides insight into what a "normal" climatic range is for a region.

Links to Drought Resources from the WDC for Paleoclimatology

• The Paleo Perspective on North American Drought provides an overview of drought in North America over the span of hundreds and thousands of years.
  
  
• The NOAA/NESDIS North American Drought Variability project uses instrumental and tree ring data to present both instrumented and reconstructed Palmer Drought Severity Index (PDSI) values as maps and gridded times series formats.
  
  
• 2000 Years of Drought Variability in the Central United States by Woodhouse and Overpeck's compares 20th century records with paleo records over the past two millennia.
  
  
• Paleoclimate Reconstructions include reconstructions of a variety of moisture-related variables such as precipitation, drought and streamflow.
  
  
• Paleoclimatic State of the Climate Reports from NOAA/NCDC.
  
  Examples of these reconstructions include:
• North American Great Plains Drought, by Laird et al. (1996) examines greater drought intensity and frequency before A.D. 1200.
  
  
• Rainfall and drought in equatorial east Africa during the past 1,100 years by Verschuren et al.
  
  
• Droughts Through Time by Jain, Hoerling
  and Woodhouse.

In addition to the long-term perspective on drought provided by the NOAA Paleoclimatology Program, there are numerous other resources within NOAA regarding drought that can be accessed through the NOAA Drought Information Center.