News Archive

Year-to-year changes in concentration of carbon dioxide and methane, two important greenhouse gases in the atmosphere, can be linked to fire activity associated with the El Nino-La Nina cycle, according to a study conducted by a team of NASA scientists and other researchers. Study results appear in an article in the Jan. 2, 2004, issue of Science. "Many scientists have attributed this atmospheric variability to changes in the balance between plant growth and microbial respiration," said James Randerson of the University of California-Irvine, one of the study's authors. "Our work indicates, however, that the sum of these two processes has a smaller impact on atmospheric carbon dioxide levels than previously believed." The scientists also determined almost all the increased levels of carbon dioxide and methane measured during 1997 and 1998 could be attributed to the worldwide fires at the time, underscoring the impact El Nino has on greenhouse gas emissions. Carbon is stored in vegetation, and when the vegetation burns, the carbon returns to the atmosphere.

Return to page index...

global change news
New Climate Monitoring Network Now Operational
NOAA announced recently that a new, high-tech climate monitoring network, designed to track the nation's temperature and precipitation trends, is now operating in 28 states. The U.S. Climate Reference Network (CRN), developed by NOAA scientists, will improve the ability of America's decision-makers to form policies about programs impacted by climate variability and change. "The climate reference network helps us fill an important land based gap of data in the United States that we will need in the larger and more comprehensive Earth observation system being developed by more than 34 countries in what could be the next 10 years," said retired Navy Vice Adm. Conrad C. Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. "With important links like the CRN, the Earth observation system will help address emerging global issues and lay the groundwork for improved environmental decision-making and economic growth and prosperity."

With more than $3 trillion of U.S. GDP affected by climate and weather, including the agriculture, energy, construction, travel and transportation industry sectors, there are powerful economic as well as environmental incentives for gaining a greater understanding of these phenomena. The United States has already made significant investments in space and in-situ or surface-based observing systems, including its ability to monitor the ozone layer using spacecraft and aircraft and the TAO/Triton Array of buoys that have helped forecast the most recent El Niño six months in advance. The CRN will provide the United States new data points in a swift and affordable manner. "The CRN will give America a first-class observing network for the next 50 to100 years that will serve as a benchmark for climate monitoring," said Gregory W. Withee, assistant administrator for the NOAA Satellites and Information Service. He made the announcement at a news conference at the American Meteorological Society’s annual meeting in Seattle.

Return to page index...

global change data
Department of Energy Releases Updated Greenhouse Gas Database
The U.S. Department of Energy's Carbon Dioxide Information Analysis Center (CDIAC) has released an updated data base from the global ALE/GAGE/AGAGE monitoring network (DB1001), which provides continuous high-frequency measurements of methane, nitrous oxide, several halogenated hydrocarbons, carbon monoxide, and hydrogen. This data base supports analyses and monitoring related to greenhouse gases and to the Earth's ozone layer. The data were contributed by R. Prinn, Massachusetts Institute of Technology; D. Cunnold, Georgia Institute of Technology; P. Fraser, Commonwealth Scientific and Industrial Research Organization (CSIRO, Australia); R. Weiss, Scripps Institution of Oceanography (SIO); P. Simmonds and S. O'Doherty, Bristol University (United Kingdom); L.P. Steele (CSIRO); P. Salameh, SIO; and R.H.J. Wang, Georgia Institute of Technology. Data through March 2003 are now available for all five existing sites: Cape Grim, Tasmania; Point Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and Trinidad Head, California (stations also previously existed at Cape Meares, Oregon, and Adrigole, Ireland).

Return to page index...

Two of the nation's premier atmospheric scientists, after reviewing extensive research by their colleagues, say there is no longer any doubt that human activities are having measurable--and increasing--impacts on global climate. Their study cites atmospheric observations and multiple computer models to paint a detailed picture of climate changes likely to buffet Earth in coming decades, including rising temperatures and an increase in extreme weather events, such as flooding and drought. The study appeared December 5 in Science as part of the journal's "State of the Planet" series. The coauthors--Thomas Karl, director of NOAA's National Climatic Data Center, and Kevin Trenberth, head of the Climate Analysis Section at the National Center for Atmospheric Research (NCAR)--conclude that industrial emissions have been the dominant influence on climate change for the past 50 years, overwhelming natural forces. The most important of these emissions is carbon dioxide, a greenhouse gas that traps solar radiation and warms the planet. "There is no doubt that the composition of the atmosphere is changing because of human activities, and today greenhouse gases are the largest human influence on global climate," they write. "The likely result is more frequent heat waves, droughts, extreme precipitation events, and related impacts, e.g., wildfires, heat stress, vegetation changes, and sea-level rise which will be regionally dependent."

Return to page index...

global change research
Increasing Greenhouse Gases Lead to Dramatic Thinning of the Upper Atmosphere
The highest layers of the Earth's atmosphere are cooling and contracting, most likely in response to increasing levels of greenhouse gases, according to a new study by scientists at the Naval Research Laboratory (NRL). This contraction could result in longer orbital lifetimes for both satellites and hazardous space debris. In a paper published February 5 in the Journal of Geophysical Research - Space Physics, John Emmert, Michael Picone, Judith Lean, and Stephen Knowles report that the average density of the thermosphere has decreased by about 10 percent during the past 35 years. The thermosphere is the highest layer in the atmosphere, and begins at an altitude of about 90 kilometers [60 miles].

This decrease in density had been predicted by theoretical simulations of the upper atmosphere's response to increasing carbon dioxide and other greenhouse gases. In the troposphere (the lowest layer of the atmosphere) greenhouse gases trap infrared radiation, causing the well-known "global warming" effect. Higher in the atmosphere, above about 12 kilometers [seven miles], however, these gases actually enhance the ability of the atmosphere to radiate heat out to space, thereby causing a cooling effect. As the amount of carbon dioxide increases, the upper atmosphere becomes cooler and contracts, bringing lower-density gas to lower heights. Consequently, at a given height, the average density will decrease. Because each layer of the atmosphere rests on the layers below it, small changes at lower altitudes become amplified at higher altitudes. The NRL study found that the observed decrease in density depends on height in the same way as predicted by the theoretical simulations, indicating that greenhouse gases are a likely source of the change.

Return to page index...

global change research
River Indicates Warmer Climate and Earlier Spring in Central Maine
"Warm" is hardly the first word most of us would think of when contemplating Central Maine's winter weather. Yet, a recent study by scientists at the U.S. Geological Survey (USGS), published in the November issue of the journal Climatic Change, suggests what long-time residents have suspected; winter in Central Maine just isn't quite what it used to be. "We compared long-term records of ice thickness and water flow for the Piscataquis River with air temperature for the surrounding area and found significant trends that are consistent with climate warming and advancing spring," said Thomas Huntington, lead author and hydrologist at the USGS Maine District Office. "During the 20th century, average winter temperatures increased by about 3 degrees Fahrenheit and ice on the Piscataquis River on about February 28 was thinner by an average of 9 inches," said Huntington. Other river-flow, temperature, and biologic data analyzed in this study and in studies completed in 1995-2001 throughout New England also consistently indicate systematic, regional late winter and early spring warming during the past century.

Return to page index...

Previous News Stories...