Bad news from above

29/09/1996
Down To Earth

the first comprehensive global analysis of National Aeronautics and Space Administration's ( nasa 's) 15-year satellite data reveals that increasing amounts of solar ultraviolet ( uv ) radiation have been hitting the earth's surface, with the thinning of the atmospheric ozone shield (see Down To Earth , Vol 5, No 7).

The nasa analysis is being called comprehensive as it takes the masking effect of clouds and pollution into account. According to atmospheric scientist, Jay R Herman of nasa 's Goddard Space Flight Centre in Greenbelt, Montana, us , the team has used a new and more accurate analytical technique. The technique, which was developed over the past year, is being used to eliminate errors and recaliberate data obtained from the total ozone mapping spectrometer or ( toms ), flown aboard the orbiting Nimbus-7 satellite. toms is a part of nasa 's Mission to Planet Earth, a long-term, coordinated research effort to study the earth as a global system. The new technique involves the use of a space-borne instrument to determine the uv-b radiation at ground level. The Nimbus-7 toms measures neither ozone nor surface uv-b radiation directly. Instead, it measures the amount of radiation scattered back through the ozone layer.

To validate the new technique, the team has compared its findings with those arrived at by ground-based spectrometers in Canada, New Zealand and South America. These earlier ground-based studies on radiation have been comparatively limited as none of them have been in operation long-enough. Moreover, their findings have not been caliberated well-enough. As a result, their findings have been controversial and have reported the decrease and even the lack of any increase in radiation.

According to Herman, "The increase in radiation is the largest in the middle and high latitudes, where the majority live and where most of the agricultural activity takes place.' "At 55

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