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in the News

Delving further into climate change
Researchers at Livermore have completed several studies to better understand climate change.
Evaluating energy technologies. Late in 2002, Livermore researchers Ken Caldeira and L. John Perkins collaborated with a team of international researchers to evaluate a series of advanced energy technologies that do not emit carbon dioxide or that limit its release to the atmosphere. The candidate technologies include terrestrial, solar, and wind energy; solar-powered satellites; biomass; nuclear fission; nuclear fusion; fission-fusion hybrids; and fossil fuels from which carbon has been removed.
The researchers concluded that current technologies are not helpful to stabilizing the climate. Says Martin I. Hoffert of New York University, lead author of the study report, “. . . scientific innovation can only reverse this trend if we adopt an aggressive, global strategy for developing alternative fuel sources that can produce up to three times the amount of power we use today. Currently, these technologies simply don’t exist—either operationally or as pilot projects.”
Assessing geoengineering schemes. Using models that simulate the interaction between global climate and land ecosystems, Livermore researchers have shown that compensating for the carbon dioxide greenhouse effect by decreasing—geoengineering—the amount of sunlight reaching the planet could create a more vigorous ecosystem.
Bala Govindsasamy, Starley Thompson, Philip Duffy, Ken Caldeira, and University of Wisconsin collaborator Christine Delire published a report in the November 26, 2002, online edition of Geophysical Research Letters. They modeled the effect of various schemes to reduce sunlight reaching Earth’s surface and determined that the reduction would have little effect on the terrestrial biosphere. “In fact,” says Caldeira, “turning down the Sun a bit reduces evaporation and therefore gives plants more water for photosynthesis so that they may actually grow better in a geoengineered world than they do today.” However, researchers strongly caution against adopting geoengineering interventions because of the risks of system failure and unpredictable responses from Earth’s climate system.
Measuring tropopause height. Climate researchers have discovered another sign of human effects on global climate. They have observed that the height of the tropopause—the transition zone between the troposphere and the stratosphere—has increased, and those increases agree with projections made by climate models of greenhouse warming. The warming affects atmospheric temperature, which in turn affects tropopause height.
The observations and modeling undercut claims that no warming has occurred during the last two decades because satellite temperature measurements of the troposphere have shown little or no warming. According to Livermore researcher Benjamin Santer, “Our best understanding is that this increase [in tropopause height] is due to two factors: warming of the troposphere, which is caused by increasing greenhouse gases, and cooling of the stratosphere, which is mainly caused by depletion of stratospheric ozone. Tropopause height changes give us independent evidence of the reality of recent warming of the troposphere.”
n addition to Santer, Livermore scientists James Boyle, Krishna Achutarao, Charles Doutriaux, and Karl Taylor teamed with researchers from the National Center for Atmospheric Research, National Aeronautics and Space Administration’s Goddard Institute for Space Studies, Max Planck Institute for Meteorology, and Institut für Physik der Atmosphäre in Germany to report their findings in the online Journal of Geophysical Research–Atmosphere.
Contact: Ken Caldeira (925) 423-4191 (caldeira2@llnl.gov) or Benjamin Santer (952) 422-7638 (santer1@llnl.gov).

Looking for small objects beyond Neptune
At the winter meeting of the American Astronomical Society in early January, a collaboration of astronomers, including several from Lawrence Livermore, presented their work to search for small, cometlike bodies in the outer solar system with four half-meter telescopes.
In normal practice, astronomers detect comet bodies by looking for the light reflected by them. But the astronomers on the Taiwanese–American Occultation Survey (TAOS) Project will instead be searching for those rare moments when one of the objects passes between telescopes and a nearby background star. During one of these brief moments, scientists will be able to study objects that are much too faint to be seen in reflected sunlight, even with the largest telescopes.
TAOS is probing the Kuiper Belt, known only through two objects (Pluto and its moon Charon) until a flood of its bodies was discovered in the 1990s. Much about the region remains unknown, but all theories about it predict that there are many more small objects than large ones. TAOS scientists believe that their technique will allow them to detect objects as small as 3 kilometers in diameter. It is believed that there are billions of objects this small in the outer solar system. “The TAOS survey will provide data on remnants of our early solar system and early planet formation,” says Livermore astronomer Kem Cook. “It will provide us insight into how the solar system evolved. We’ll be looking at the smallest objects that anyone has seen.”
The collaboration is made up of scientists from the Institute of Astronomy and Astrophysics in Taiwan, University of Pennsylvania, National Central University in Taiwan, Yonsei University in South Korea, and National Aeronautics and Space Administration as well as Livermore.
Contact: Kem Cook (925) 423-4634 (cook12@llnl.gov).