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 Washington, December
15 — NOAA Scientists reported today that droughts more severe than the 1930s Dust Bowl
could occur in the Great Plains sometime in the next century.
Click here for graphics.
Connie Woodhouse, a University
of Colorado research scientist working at NOAA's National
Geophysical Data Center in Boulder, Colo., and Jonathan Overpeck,
head of NOAA's Paleoclimatology
Program, report the results of their research in the December
issue of the Bulletin of the American Meteorological Society.
The authors reviewed existing
paleoclimatic literature, including a variety of data sources,
to determine what droughts were like before instruments were
invented, and to compare droughts of the past 2000 years with
more recent droughts. The data sources consist of historical
documents, tree rings and archaeological remains, as well as
lake, river and wind-blown sediments.
The authors found a greater range
of drought variability in the past than found in the instrumental
record. Droughts of the 20th century have been only moderately
severe and relatively short, compared with droughts of much longer
ago. Woodhouse said that paleoclimatic records of the past 400
years strongly indicate that the severe droughts of the 20th
century, the 1930s Dust Bowl and the l950s drought, were not
unusual events and suggest that we can expect to have droughts
of this magnitude once or twice a century.
"However, when we look even
farther back in time, we see indications of droughts with much
greater duration," said Woodhouse. During the 13th to 16th
centuries, there is evidence for two major droughts that probably
significantly exceeded the severity, length, and spatial extent
of 20th century droughts, the authors report. The most recent
of these "megadroughts" occurred throughout the western
United States in the second part of the 16th century. This drought
appears to have been the most
severe and persistent drought in the Southwest in the past 1000
to 2000 years. Another megadrought occurred in the last quarter
of the 13th century.
"Conditions that lead to
severe droughts such as that of the late 16th century could recur
in the future, leading to a natural disaster of a dimension unprecedented
in the 20th century," Overpeck said. "Besides the fact
that natural variability could have more severe droughts in store
for us in the future, two human factors could make the Great
Plains even more susceptible to a severe drought in the future.
These are land use practices and global warming."
"Even in the absence of
significant greenhouse warming, however, future droughts may
be much more severe and last much longer than what we have experienced
this century," Woodhouse said.
Overpeck said that paleoclimatic
data in combination with instrumental data, satellite observations,
and climate models are essential to understanding the full range
of natural drought variability, and also to reduce uncertainty
with respect to what human-induced and natural climatic change
will occur in the future. |
