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 5, NUMBER 11, NOVEMBER 1992
GENERAL INTEREST--OZONE DEPLETION, STRATOSPHERIC AEROSOLS
"A Decrease in the Growth Rates of Atmospheric Halon Concentrations,"
J.H. Butler (CMDL, NOAA, 325 Broadway, Boulder CO 80303), J.W. Elkins et al.,
Nature, 359(6394), 403-405, Oct. 1, 1992.
A six-year record shows that the growth rates of the tropospheric mixing
ratios of the commonly used halons H-1301 and H-1211 have already begun to
decrease substantially through the influence of the Montreal Protocol. This
decrease is consistent with industry emission estimates, supports current
appraisals of atmospheric lifetimes, and suggests levels will stabilize or begin
to decrease within the next few years.
Two items from Nature, 359(6393), Sep. 24, 1992:
"Volcanic Aerosols Implicated," G. Brasseur (NCAR, POB 3000,
Boulder CO 80307), 275-276. Discusses recent papers on the relationship between
volcanic aerosols and ozone depletion by anthropogenic chemicals, particularly
the following by Hofmann et al.
"Observation and Possible Causes of New Ozone Depletion in Antarctica
in 1991," D.J. Hofmann (CMDL, NOAA, 325 Broadway, Boulder CO 80303), S.J.
Oltmans et al., 283-287. Local ozone reductions approaching 50% were observed
during the Antarctic spring at two altitudes where depletion had not been
observed previously, 11-13 km and 25-30 km. Depletion at the lower level
coincided with enhanced volcanic aerosol particles from the August 1991 eruption
of Mount Hudson in Chile, and apparently resulted from heterogeneous processes
on those particles. Depletion in the upper layer appears to have been associated
with transport of air from a region of enhanced polar stratospheric clouds.
"Increased Ultraviolet Radiation in New Zealand (45° S)
Relative to Germany (48° N)," G. Seckmeyer (GSF, Inst. Biochem.
Pflanzenpathol., Inglostädter Landstr. 1, D-8042 Neuherberg, Ger.), R.L.
McKenzie, ibid., 359(6391), 135-137, Sep. 10, 1992.
Uses a combination of spectral measurements made in Germany and New Zealand
with the same spectroradiometer, together with model calculations, to show that
in the New Zealand summer of 1990-91 biologically weighted UV irradiances were
nearly a factor of two greater than those in the summer at similar northern
latitudes in Germany. These unexpectedly large differences are due mainly to
decreased stratospheric ozone over New Zealand and increased tropospheric ozone
"Enhancements in Biologically Effective Ultraviolet Radiation
Following Volcanic Eruptions," A.M. Vogelmann (Dept. Meteor., Pennsylvania
State Univ., Univ. Pk. PA 16802), T.P. Ackerman, R.P. Turco, ibid., 359(6390),
47-49, Sep. 3, 1992.
Although volcanic particles may induce ozone destruction through
heterogeneous chemical reactions, the effect of ozone reductions on UV reaching
the Earth's surface is not obvious, because aerosols also reflect
sunlight. Here a radiative transfer model is used to show that
biologically-effective radiation at the surface increased in the cases of
particles produced by both the El Chichón (1982) and Mount Pinatubo
(1991) eruptions, because the effect of ozone depletion was dominant.
"Mount Pinatubo Aerosols, Chlorofluorocarbons and Ozone Depletion,"
G. Brasseur (NCAR, POB 3000, Boulder CO 80307), C. Granier, Science,
257(5074), 1239-1242, Aug. 28, 1992.
Uses a latitude-altitude global model describing chemical, radiative and
dynamical processes to show that changes in the solar and infrared radiation
budget caused by the eruption should produce a cooling of the troposphere and a
warming of the lower stratosphere, which could affect atmospheric circulation.
In addition, heterogeneous chemical reactions on the surfaces of sulfate aerosol
particles render the ozone molecules more vulnerable to anthropogenic chemicals.
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