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While scientists have learned to interpret receding glaciers as well as changing trends in snow cover, sea ice extent, and sea level as "indicators" of climate change, they are still working to better understand the role that frozen soils play within the Earth's climate system. NOAA Climate and Global Change Program administrators recently funded Tingjun Zhang, research associate at the National Snow and Ice Data Center, Cooperative Institute for Research in the Environmental Sciences, and his colleague, Richard Armstrong, to investigate the seasonal freeze-thaw cycles of soils. Their investigation is an important part of the larger Global Energy and Water Cycle Experiment (GEWEX) Continental-Scale International Project (GCIP) study regions, centered on the Mississippi River Basin.

"Research on the effects of frozen soil indicates that it has a significant influence on land surface and overlying atmospheric processes," Zhang says. "The timing, duration, thickness and distribution of frozen soils are primarily controlled by heat exchange between the atmosphere and land surface. Changes in any of these events are good indicators of climate change."

global change research
The Causes of 20th Century Warming
Global air surface temperatures increased by about 0.6°C during the 20th century, but as Francis Zwiers and Andrew Weaver discuss in their Perspective in the 15 December issue of Science, the warming was not continuous. Two distinct periods of warming, from 1910 to 1945 and since 1976, were separated by a period of very gradual cooling. The authors highlight the work by Stott et al.--published in the same issue--who have performed the most comprehensive simulation of 20th century climate to date. The agreement between observed and simulated temperature variations strongly suggests that forcing from anthropogenic activities, moderated by variations in solar and volcanic forcing, has been the main driver of climate change during the past century.

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New Report Suggests that Climate Change May Have Serious Impacts on National Water Resources
Latest in a series of reports expected from the U.S. National Assessment predicts changes in runoff, rising sea levels, and increased risks of flooding
On 15 December, the Pacific Institute and the Department of the Interior released a new report titled Water: The Potential Consequences of Climate Variability and Change for the Water Resources of the United States, prepared as part of the U.S. Global Change Research Program's National Assessment of the Potential Consequences of Climate Change.

The report, a two-year compilation of scientific studies by representatives of the government, corporate and non-governmental organization sectors to evaluate the implications of both existing climate variability and future climate change on national water resources was prepared under the leadership of the Pacific Institute. It concludes that climate changes in this century may have serious implications for U.S. water resources.

"This reports is another reminder that climate change is upon us, and a wake up call that we need to begin long range planning efforts to prepare for the eventuality of global warming," said Deputy Secretary of the Interior David J. Hayes. "The good news is that the analysis and findings in this report are the basis for beginning that planning process now," Hayes added.

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global change research
New Study Shows Global Warming Trend Greater without El Niño and Volcanic Influences
Removing the masking effects of volcanic eruptions and El Niño events from the global mean temperature record reveals a more gradual and yet stronger global warming trend over the last century, according to a new analysis by Tom Wigley, a climate expert at the National Center for Atmospheric Research (NCAR). The analysis supports scientists' claim that human activity is influencing the earth's climate. The findings are published in the 15 December issue of Geophysical Research Letters. NCAR's primary sponsor is the National Science Foundation.

"Once the volcanic and El Niño influences have been removed," says Wigley, "the overall record is more consistent with our current knowledge, which suggests that both natural and anthropogenic influences on climate are important and that anthropogenic influences have become more substantial in recent decades."

Volcanic emissions cool the planet by blocking sunlight, while El Niño events raise global temperatures through warmer ocean waters. Sometimes the two occur simultaneously, muddying evidence of any underlying warming trend. During the past two decades, two massive volcanic eruptions--El Chichón in April 1982 and Mt. Pinatubo in June 1991--coincided with significant El Niños, making trend detection more difficult.

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