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Global Warming Can Impact Monsoons and Lower Crop Production
New research
shows abrupt climate change over 14,000 years ago associated with a shift in
monsoon patterns and a decline in vegetation growth
Oxygen gas in ice cores has shown
evidence for abrupt climate change.
June 11, 2009
When the climate warmed relatively quickly about 14,700 years ago, seasonal
monsoons moved northward. Prior to that, the monsoons were dropping more rain
on the Earth's oceans at the expense of tropical areas, according to climate
researchers.
In an article to be published in the June 12 issue of the journal Science,
researchers from the Desert Research Institute in Nevada, the Scripps
Institution of Oceanography and Oregon State University present their findings
after comparing oxygen isotopes in air that was captured in ice cores and
previously published data from ancient stalagmites found in caves. The
research was supported by the National Science Foundation.
The ice cores, gathered from different locations in Antarctica and Greenland,
contain air bubbles that were trapped as the ice formed over tens of thousands
of years. By measuring the amount of certain oxygen isotopes in those air
bubbles, the researchers were able to determine patterns in vegetation growth
worldwide over that same span of time.
The researchers found that beginning about 14,700 years ago, the mixture of
oxygen isotopes began to change in a way that suggests more vegetation growth,
and this process continued for at least 200 years. The researchers then
compared these findings with data from an earlier study that determined the
amount of rainfall that fell in China over many millennia by examining
stalagmites in caves. They discovered that this period of low vegetation
growth corresponded with a time of reduced monsoon rainfall.
By climate standards, the researchers say, this shift happened abruptly over a
few decades. They also caution that observations of past climate events may
not be able predict future conditions. Given the vital roll that monsoons play
in sustaining billions of people, however, this connection between climate
change and monsoon patterns may be an ominous sign of what climate change in
the 21st century may bring.
Media Contacts
Dana W. Cruikshank, NSF (703) 292-7738 dcruiksh@nsf.gov
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