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

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.