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Concept
Scientific Assessment of Ozone Depletion
Summary
The Scientific Assessment of Ozone Depletion is a sequence of reports sponsored by WMO/UNEP. The most recent report is from 2018. The reports were set up to inform the Montreal Protocol and amendments about ozone depletion.
Ozone depletion and global warming
The Montreal and Vienna conventions were installed long before a scientific consensus was established. Until the 1980s, EU, NASA, NAS, UNEP, WMO and the British government had all issued further different scientific reports with dissenting conclusions. Sir Robert (Bob) Watson, Director of the Science Division of at National Aeronautics and Space Administration (NASA), played a crucial role in achieving unified reporting. The IPCC started from scratch with a more unified approach.
In the troposphere observations show that the total abundance of ozone-depleting compounds continues to decline slowly from the peak that occurred in 1992-1994.
Observations in the stratosphere indicate that the total chlorine abundance is at or near a peak, while bromine abundances are probably still increasing.
Analyses of air trapped in snow since the late 19th century have confirmed that non-industrial sources of the CFCs, halons, and major chlorocarbons were insignificant. The data suggest that substantial natural sources exist for atmospheric methyl bromide (CH3Br).
The abundances of HCFCs in the troposphere continue to increase.
water vapour is a greenhouse gas that has a greater overall effect on the ozone layer than carbon dioxide because of its higher concentrations but is not affected by human activities as it is caused mainly by evaporation and condensation rates.
Springtime Antarctic ozone depletion due to halogens has been large (40-50%; exceptionally 70%) throughout the last decade.
In some recent cold Arctic winters during the last decade, maximum total column ozone losses due to halogens have reached 30%, but in warmer winters Arctic ozone loss is small.
Ozone remains depleted in the midlatitudes of both hemispheres.
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