February 28, 2007
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A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 9, NUMBER 1, JANUARY 1996
OZONE DEPLETION: UV MEASUREMENT
Two related items in Nature, 377(6551), Oct. 26, 1995:
"The Radiation Equation," S. Madronich (Atmos. Chem. Div., NCAR,
POB 3000, Boulder CO 80307), 682-683. Discusses the results of the next paper.
Perhaps the biggest uncertainty in the study concerns the validity of
extrapolating past ozone trends into the next centuryan issue that has as
much to do with humankind's ability to restrain its growing influence on
atmospheric composition as it does with atmospheric processes.
"Effects of Clouds and Stratospheric Ozone Depletion on Ultraviolet
Radiation Trends," D. Lubin (Calif. Space Inst., Univ. California, La Jolla
CA 92093), E.H. Jensen, 710-713. Uses global satellite measurements of cloud
reflectance to estimate the potentially large natural variability in UV
radiation resulting from variations in cloud opacity. Compares this UV
variability with trends in UV radiation calculated to accompany observed trends
in total ozone abundance. By the end of this century, throughout many temperate
regions, trends in summer average local-noon UV radiation dose rates relevant to
mammalian skin cancer or plant damage will be significant compared to cloud
variability. At some locations, this is already true.
"Trends and Interannual Variations in Erythemal Sunlight, 1978-1993,"
J.E. Frederick (Dept. Geophys. Sci., Univ. Chicago, 5734 S. Ellis Ave., Chicago
IL 60637), C. Erlick, Photochem. & Photobiol., 62(3),
476-484, Sep. 1995.
Attempts to define the long-term variability in solar UV irradiance received
by selected regions of the Earth by incorporating the effects of cloudiness into
estimates of UV irradiance, using a combination of measurements and numerical
models. Although the general decline in ozone amounts over the period acted to
increase erythemal (biologically active) irradiance, the changes tend to be
obscured by the erratic variability associated with cloudiness, effectively
widening the error bars for any estimate of trend. Over a period of 10-15 years
it is questionable whether ground-based data sets will be able to establish the
existence of a nonzero trend in erythemal irradiance at the 95% confidence
level. A more detailed statistical analysis of this issue is warranted.
"Increased UV Exposure in Finland in 1993," K. Jokela (Ctr.
Radiation & Nuclear Safety, POB 14, FIN-00881 Helsinki, Finland), K.
Leszczynski et al., ibid., 62(1), 101-107, July 1995.
Evaluates the UV exposure to the Finnish population during the period of
exceptionally low ozone in April-May 1993, using measurements and theoretical
calculations. Compared to periods of average ozone level, the erythemal UV
falling onto horizontal surfaces on clear days increased 10% on average, with a
maximum increase of 34%.
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