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USGCRP
Program Elements
Atmospheric Composition
Ecosystems
Global Carbon Cycle
Decision-Support Resources Development and Related Research on Human Contributions and Responses
Climate Variability
and Change The
Global
Water Cycle
Observing and Monitoring the Climate System
Communications
International Research and Cooperation
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The following are some of
the USGCRP's major accomplishments related to Paeloenvironment & Paleoclimate
during Fiscal Year 2000:
Recent
progress in synthesizing various proxy records of past climates enables
placement of 20th century climate warming within a longer-term perspective.
Recent results indicate that much of the variability during the past 1,000
years prior to the rise in emissions of greenhouse gases from human activities
(beginning in about 1850) can be attributed to pulses of volcanism or
changes in the output of the Sun's energy. Neither of these mechanisms -- or
natural climate variability in the ocean-atmosphere system -- can explain
the late 20th century rise in the globally averaged surface temperature.
Greenhouse gases appear to emerge as the dominant forcing during the 20th
century. According to proxy temperature records, the 1990s appear to have
been the warmest decade (and 1998 the warmest year) in the past 1,000
years.
A
partnership between two sets of researchers has resulted in the acquisition
of ice core and meteorological data from the Sajama ice cap in Bolivia.
This research has provided a record of glacial versus interglacial tropical
climate dynamics over the past 25,000 years and is contributing to a better
understanding of past and present tropical Pacific climate variability.
Note: As of October
2000, this category is mostly covered under the broad "Climate
Variability and Change" research element. However
categorized on this web site, paleoenvironment and paleoclimate continues
to be an important element of global change research
and is essential to our understanding not only of the past but of future climate change.
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