Ozone Depletion, Greenhouse Gases, and Climate Change (1989) / Chapter Skim
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5 The Role of Halocarbons in Stratospheric Ozone Depletion
5 The Role of Halocarbons in Stratospheric Ozone Depletion
Pages 33-47
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From page 33... ...
, intensive measurements have been made with automatic gas chromatography operating at five stations most of the time since July 1978. These GAGE measurements through 1983 for dichIorodifluoromethane (CCI2F2, known as CFC-12)
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From page 34... ...
(Note nonzero origin of ordinate.) CFCs rising rapidly during the 1980s, with the Southern Hemisphere lagging behind the Northern Hemisphere by about 10 percent.
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From page 35... ...
, together with January flask data obtained in Oregon (upper dots) and at the South Pole (lower dots)
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From page 36... ...
In 1974, the Northern Hemisphere contained chlorine compounds at about 1.8 ppbv; this has now increased to about 3.5 ppbv. Continued release at 1986 rates will result in increases to over 5.0 ppbv by the year 2000 (Figure 5-4~.
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From page 37... ...
of stratospheric chlorinated molecules assuming (1) continued release of CFCs at 1986 rates (solid curves)
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From page 38... ...
Neil Harris, University of California at Irvine, has examined the monthly averages of the data taken daily at Arosa. The amount of stratospheric ozone at Arosa, and generally in the north temperate zone, varies seasonally, with a peak in March or April and a minimum in October or November.
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From page 39... ...
Numerous factors are believed to affect the concentration of stratospheric ozone. The solar sunspot cycle affects the ozone concentration because there is increased UV radiation at around 200 nm during the sunspot maximum.
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From page 40... ...
between the periods August 1931 to December 1969 and January 1970 to July 1986. Negative values indicate lower ozone concentrations during the later period.
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From page 41... ...
In order to determine long-term ozone trends, Rumen Bojkov from the Atmospheric Environment Service in Canada, Peter Bloomfield, a statistician from North Carolina State University, Neil Harris, and T have compiled data from all the Dobson stations and the Soviet stations by latitude bands. (The Soviet stations use a different instrument, the M-83, with somewhat different characteristics but qualitatively similar measurement techniques.)
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From page 42... ...
_ - 1 5 _ 5 _ o 5 - 1 0 5 r O _5 - 1 0 - 1 5 F SHERWOOD RO WLAND PERCENT | OZONE CHANGE t 53°N ~ 64°N 1969 ~ 1986 I 1 1 1 1 1 1 1 1 1 1 1 JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN b t , , f PERCENT t t OZONE CHANGE 40-N - 52°N 1969 - 1986 -15 + , ~ I I ~ ~ t JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN C t ~ " ' + t ~ I t t ~ PERCENT OZONE CHANGE 30- N - 39°N 1969 - 1986 JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN FIGURE 5-7 Percent change in total column ozone between 1969 and 1986 as a function of month for three Northern Hemisphere latitude bands.
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From page 43... ...
In conclusion, the amount of measured ozone loss in the summer is in reasonable agreement with theory, but the amount of loss poleward of 40°N latitude in winter is greater than that indicated by theoretical calculations. The statistical analysis suggests that there is something missing from the atmospheric models of ozone depletion that affects ozone levels in the Northern Hemisphere in winter.
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From page 44... ...
F SHERWOOD ROWLAND LATITUDE BAND 40°N- 52°N MONTHLY L I NEAR REGRESSION COEFFICIENTS WITH SUCCESSIVE YEARS OF DATA, 1965 TO 1980 198 1 1982 1983 1984 1985 1986 :~ 11I o DEC o JAN o FEB o MAR ~O APR -2 ~ ~ ~ MAY 3 _ - 4 FIGURE 5-8 Computed regression coefficients for linear change in ozone concentrations after 1969, using data for the periods 1965 to 1980, 1965 to 1981, and 1965 to 1982 through to 1986 for each calendar month for the latitude band 40°N to 52°N.
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From page 45... ...
O m o C) - 1 -2 3 4 LATITUDE BAND 40°N-52°N MONTHLY LINEAR REGRESSION COEFFICIENTS WITH SUCCESSIVE YEARS OF DATA, 1965 TO 1980 198 1 1982 1983 1984 1985 1986 11t Tll tll Ili ITI ~ T FIGURE 5-8 (continued)
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From page 46... ...
Hence, the tropospheric contribution is increasing total ozone at a rate of about ~ percent per decade. If correct, this means that the stratospheric ozone losses are somewhat greater than the total ozone column measurements indicate because of the increase in tropospheric ozone.
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From page 47... ...
1984. Analysis of upper stratospheric Umkehr ozone profile data for trends and the effects of stratospheric aerosols.
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