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The Laboratory
in the News

Space technologies adapted to fight terrorism
Detection technologies developed by Livermore researchers to study astrophysical phenomena such as black holes and supernovas have a new down-to-earth application—helping to fight terrorism. Now, technologies for finding and imaging space phenomena are assisting in the detection of nuclear materials or devices.
One such technology is the High-Energy Focusing Telescope (HEFT), scheduled to be launched in the fall of 2003. HEFT will be used primarily to study how supernovas create and distribute most of the elements heavier than helium. The telescope’s integrated circuits work in conjunction with cadmium–zinc–telluride crystals to detect and measure faint gamma-ray signals. HEFT’s mirrors focus the gamma rays into imaging detectors to produce clear pictures with high spectral resolution.
Simon Labov, the director of Livermore’s Radiation Detection Center, explains that “In both astrophysics and nuclear materials, the emissions are faint, and there is a lot of background noise. Having advanced high-sensitivity detectors can solve both problems. In effect, the efforts of about 50 researchers and $20 million spent during the past 5 years is being leveraged for detecting nuclear materials” to combat terrorism and support homeland security.
Detector technologies for studying black holes in space will also be used in small hand-held detectors for finding and analyzing nuclear materials on Earth.
Contact: Simon Labov (925) 423-3818 (labov1@llnl.gov).

Uncertainties found in global warming satellite data
Using a new analysis of satellite temperature measurements, a research team including Livermore scientists has discovered that satellite data used to measure temperature changes in various layers of the atmosphere contain uncertainties that may hamper the detection of human effects on climate change.
Since 1979, microwave sounding units (MSUs) flown on 12 polar-orbiting U.S. weather satellites have measured the microwave emissions of oxygen molecules, which are related to atmospheric temperature. By monitoring these emissions at different frequencies, researchers can work backward to determine temperature changes in various layers of the atmosphere.
Analysis of MSU data, which until recently was done solely by researchers from the University of Alabama at Huntsville, has indicated little or no warming of the troposphere (the lowest layer of the atmosphere) since 1979. These findings bring into question both the reality of human-induced global warming and the reliability of computer climate models that predict tropospheric warming in response to increases in greenhouse gases. The University of Alabama results are also at odds with thermometer measurements indicating pronounced warming of Earth’s surface during the satellite era.
Analysis of MSU data is, however, complicated by factors such as the gradual decay and drift of satellite orbits, which affect the time of day at which MSUs measure atmospheric temperatures, and by problems with MSU calibration.
Recently, a group of researchers led by Carl Mears, Matthias Schabel, and Frank Wentz of Remote Sensing Systems in Santa Rosa, California, conducted an independent analysis of the raw MSU data. Using different methods to correct for satellite orbital drift and calibration problems, they found that the troposphere probably warmed by roughly 0.18°F per decade from 1979 to 2001, for a total rise in tropospheric temperature of 0.4°F over that period.
Livermore scientists Benjamin Santer, Karl Taylor, James Boyle, and Charles Doutriaux, along with researchers from Remote Sensing Systems, the National Center for Atmospheric Research, Lawrence Berkeley National Laboratory, and the University of Birmingham in England, are exploring the implications of these uncertainties for the study of human effects on climate. Their findings are reported in the May 1, 2003, edition of Science Express, the online publication of Science magazine.
The team’s modeling yielded detailed patterns, or fingerprints, of tropospheric temperature change. These fingerprints are identifiable in the Remote Sensing Systems analysis of MSU data showing a warming troposphere, but not in the University of Alabama analysis.
According to Livermore’s Santer, lead author of the Science Express paper, “In the last 24 years, satellites have helped us observe the climate of our planet more intensively and systematically than at any other time in Earth’s history. Yet even over the satellite era, there are still large uncertainties in our estimates of how tropospheric temperatures have changed. It’s important to take these uncertainties into account in evaluating the reliability of climate models. . . . Our detection results point toward a real need to reduce current levels of uncertainty in satellite temperature measurements.”
Contact: Benjamin Santer (925) 422-7638 (santer1@llnl.gov).

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UCRL-52000-03-6 | June 24, 2003