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GLOBALÝWARMINGÝNEWS
By Sean Henahan, Access Excellence BOSTON, MA (4/18/97) Recent satellite analysis shows an hitherto unexpected increase in photosynthesis in the northern hemisphere associated with a global warming trend, while ground observations in the tropics also report disturbing meteorological trends.  Researchers
at Boston University base their findings on analyses of data from three
National Oceanic and Atmospheric Administration (NOAA) weather satellites.
The satellites measure light reflected from the Earth's surface. By comparing
the ratio of infrared to visible light, the researchers can estimate vegetation
growth in a given area. The studies suggest that Spring now
comes one week earlier than it did in the early 1970's.
Caption: Llamas ponder the shrinking ice-cap (click for larger version) The period since 1980 has been the warmest in the past 200 years. The data from the satellites revealed that, on average, photosynthesis between latitudes 45 degrees N and 70 degrees N increased by about 10% between 1981-91. This area includes Boston, Bordeaux and Vladivostok. The data also showed that snow was disappearing about a week earlier in these areas than previously. Variations in the timing of the growing season are closely connected with the seasonal cycle in carbon dioxide concentration in the atmosphere, a cycle that is superimposed on a general long-term rise (and which is partly responsible for making the underlying trend so hard to spot). This cycle is the result of both plant growth and plant respiration and therefore strongly associated with the seasonal cycle in surface temperature, the researchers note. "Both the satellite data and the CO2 record indicate that the global carbon cycle has responded to interannual fluctuations in surface air temperature which, although small at the global scale, are regionally highly significant," said lead investigator Ranga B Myneni. "It's a marvelously provocative article," says Inez Fung, a global change scientist at the University of Victoria in British Columbia. "They convinced me that there's a positive trend, but I'm not sure about the magnitude ... 10% over a decade--that's a whopping number." The study will certainly stimulate debate, Fung predicted. Satellite sensors may be suspect, and the conclusions of this study represent extrapolations from a very small observed change. Nonetheless, the data are compelling and have yet to be disproved, noted Fung. More evidence suggesting global warming was presented at the Association of American Geographers in Fort Worth, TX. Ohio State University researchers reported that some of the most compelling evidence yet for recent global warming may be found in the tropics and subtropics, rather than in the polar regions where early signs of warming are anticipated. For example, ice caps in alpine regions throughout the tropics and subtropics are melting at a phenomenal rate. Moreover, other scientists discovered last year that the freezing point in the upper atmosphere has been gaining altitude. These findings, may be among the best evidence to date that the planet is experiencing a recent and rapid warming, said Ellen Mosley-Thompson, a professor of geography at Ohio State. The reported evidence includes:
"Most of the evidence for warming that we see in these high alpine ice caps is in regions that are already water stressed. These tropical areas are where most of the planet's population lives and where subsistence agriculture is incapable of feeding the population. And in the future, the greatest increase in population will occur here, Mosley-Thompson said. For years, scientists have argued whether the evidence for changes in world climate were being hidden behind normal climate variations. The Ohio State team now believes that the evidence is getting stronger at the same time our ability to decipher it has improved dramatically. They cited the loss of ice volume in the tropical and subtropical ice caps, in the Antarctic Peninsula, and in the Russian Arctic, along with increased snowfall over East Antarctica as further evidence of change. "We're making massive changes to the climate on an unprecedented scale in some parts of the globe," she said. "This kind of discussion has to find its way into the general conversation." There is wide disagreement currently on the topic of global warming. Another recent study by scientists at the National Center for Atmospheric Research (NCAR) questioned the use of temperature-measuring satellites for measuring global climate change. Other critics have recently published overviews on the potential limitations of using computer models that mimic the earth's atmosphere for research on climate change. Dr. Myneni's research appears in the April 17, 1997 issue of Nature. The NCAR research appeared in the March 13, 1997 issue of Nature (Hurrell et al.). The Association of American Geographers conference took place April 3, 1997. Related information on the Internet NOAA Climate Prediction Center Atmosphere & Climate Links Scientific American, 5/97: The Coming Climate AEÝActivity: Gaia Science Update: 2/14/97- Global .Weather Science Update: 4/96- CO2 Threat & Global Warming
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