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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 5, NUMBER 11, NOVEMBER 1992

PROFESSIONAL PUBLICATIONS...
GENERAL INTEREST--OZONE DEPLETION, STRATOSPHERIC AEROSOLS

Item #d92nov11

"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.

Item #d92nov12

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.

Item #d92nov13

"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 over Germany.

Item #d92nov14

"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.

Item #d92nov15

"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.