My thanks to talkshop reader Jamal Munshi for alerting me to his paper on ozone and aerosols. It makes a strong case for viewing the ozone level above the Antarctic as a special case due to its unique geography, calling into question conclusions about human emissions drawn by scientists and acted on by the Montreal protocol. This is important as this agreement has been used as a template for ‘climate action’ subsequently.
The overall structure of changes in total column ozone levels over a 50-year sample period from 1966 to 2015 and across a range of latitudes from -90o to +71o shows that the data from Antarctica prior to 1995 represent a peculiar outlier condition specific to that time and place and not an enduring global pattern. The finding is inconsistent with the RowlandMolina theory of chemical ozone depletion. 1 1.
In 1971, renown environmentalist James Lovelock studied the unrestricted release of halogenated hydrocarbons (HHC) into the atmosphere from their use as aerosol dispensers, fumigants, pesticides, and refrigerants. He was concerned that (1) these chemicals were man-made and they did not otherwise occur in nature and that (2) they were chemically inert and that therefore their atmospheric release could cause irreversible accumulation. In a landmark 1973 paper by Lovelock, Maggs, and Wade he presented the discovery that air samples above the Atlantic ocean far from human habitation contained measurable quantities of HHC (Lovelock, Halogenated hydrocarbons in and over the Atlantic, 1973). It established for the first time that environmental issues could be framed on a planetary scale and it served as the first of three key events that eventually led to the Montreal Protocol and its worldwide ban on the production, sale, and atmospheric release of HHC (UNEP, 2000).
Total column ozone data for each calendar month3 from twelve ground stations in a large range of latitudes are studied in a fifty-year sample period4 from 1966-2015. The study period is divided into ten Lustra. The average seasonal cycle within each Lustrum and the trends for each calendar month from Lustrum to Lustrum are compared across the range of latitudes from -90o to +71o in the sample period. The overall structure of changes in total column ozone in time and across latitudes shows that the data from the two stations in Antarctica prior to 1995 are unique and specific to that time and place. They cannot be generalized into a global pattern of ozone depletion. The findings imply that declining levels of total column ozone in Antarctica during the months of October and November prior to 1995 do not serve as empirical evidence that can be taken as validation of the Rowland-Molina theory of chemical ozone depletion.
The chemical theory implies ozone depletion across a greater range of latitudes and over a much longer period of time than what was found in the data. It is far more likely that the historical decline of total column ozone in the South Pole during the months of October and November are related to natural cycles in atmospheric circulation patterns that transport ozone from the tropics to the South Pole. All data and computational details used in this study are available in the online data archive for this paper (Munshi, Ozone paper data archive, 2016).