SUMMARY: 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 1985 are unique and specific to that time and place. They cannot be generalized into a global pattern of ozone depletion.

Here we show that declining levels of total column ozone in Antarctica during the months of October and November prior to 1985 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 that ozone depletion must be assessed across the full range of latitudes and over a much longer time span than what is found in Farman etal 1985 which serves as the sole basis for the ozone depletion hypothesis that led to the Montreal Protocol and the ascendance of the UN as a global environmental authority.

Details below. 

FIGURE 1: ROLAND MOLINA THEORY OF OZONE DEPLETION BY CHLORINE

FIGURE 2: THE FARMAN ETAL 1985 FINDINGS

TABLE 1: MEASURING STATIONS USED IN THE STUDY

DATA#1: AMS SOUTH POLE, ANTARCTICA

DATA#2: HLB, HALLEY BAY, ANTARCTICA

DATA#3: LDR, LAUDER, NEW ZEALAND

DATA#4: PTH, PERTH, AUSTRALIA

DATA#5: SMO, AMERICAN SAMOA

DATA#6: MLO, MAUNA LOA

DATA#7: WAI, WALLOPS ISLAND, VA

DATA#8: BDR, BOULDER, CO

DATA#9: CAR, CARIBOU, ME

DATA#10: BIS, BISMARK, ND

DATA#11: FBK, FAIRBANKS, AK

DATA#12: BRW, BARROW, AK

SUMMARY#1: LATITUDINAL PATTERNS AND HEMISPHERIC ASYMMETRY

SUMMARY#1 shows that the range of observed ozone levels is a strong function of latitude. It reaches a minimum of about 20DU in the tropics and increases asymmetrically toward the two poles. The hemispheric asymmetry has two dimensions. The northward increase in range is more gradual than the steep southward increase in range. Also, the northward increase in range is achieved mostly with a greater frequency of high values while southward increase in range is achieved mostly with a declining frequency of low values. The midpoint between the HIGH and LOW values is symmetrical within ±45 latitude but diverges sharply beyond 45 latitude with the northern leg continuing to rise while the southern leg changes to a steep decline. Hemispheric asymmetry in atmospheric circulation patterns is well known (Butchart, 2014) (Smith, 2014) and the corresponding asymmetry in ozone levels is also recognized (Crook, 2008) (Tegtmeier, 2008) (Pan, 1997). These asymmetries are also evident when comparing seasonal cycles among the ground stations. The observed asymmetries are attributed to differences in land-water ratios in the two hemispheres with specific reference to the existence of a large ice covered land mass in the South Pole (Oppenheimer, 1998) (Kang, 2010) (Turner, 2009). The climactic uniqueness of Antarctica is widely recognized (Munshi, Mass Loss in the Greenland and Antarctica Ice Sheets, 2015) (NASA, 2016) (NASA, 2015).

SUMMARY#2: THE SEASONAL CYCLE AT DIFFERENT LATITUDES

The ground stations in SUMMARY#2 are sorted by latitude from south to north. The right panel shows the relative amplitudes of the seasonal cycles at the twelve ground stations. The left panel indicates the time structure of the seasonal cycle. It shows that at all northern hemisphere stations north of 30 latitude, the seasonal cycle runs from a low in the northern autumn months of September-November to a high in the northern spring months of March-May. In the very shallow seasonal cycles in the northern tropics (MLO) the seasonal low changes from the northern autumn to the northern winter months of December-February but the seasonal high remains at the northern spring months of March-May. Once we cross the equator to the southern tropics the seasonal cycle change abruptly. The low remains at December-February but the seasonal high changes to the southern spring months of September to November. This reversal persists into the southern mid-latitudes down to 60 degrees south where we find that the seasonal low occurs at the southern autumn months of March-May with a high in the southern spring months of September-November. In terms of calendar months the southern ozone cycle is a mirror image of the northern ozone cycle but of course, in terms of seasons, they are exactly the same. Thus, no asymmetry in ozone cycles exists between the hemispheres within ±60o latitude. However, a dramatic asymmetry is found in the continent of Antarctica. Here we find a perfect 180-degree reversal of the seasonal cycle with a high in the southern summer (December-February) and a low in the southern spring (September to November). The timing of the seasonal cycle shown in the left panel of Figure 29 demonstrates the uniqueness of Antarctica. The size and location of the amplitude of the seasonal cycle further underscores Antarctica’s peculiarity on a global scale because it is fairly symmetrical within ±60 degrees but this symmetry is lost when we enter the higher latitudes. In the north, the HIGH value continues to rise from 350DU to well above 400DU while the LOW is stable at above 250 DU. The exact reverse of this pattern is seen in the south where the HIGH is stable at 350DU while the low collapses from 250DU to below 150DU. These data do not indicate that ozone depletion observed in Antarctica from 1975 to 1985 (Farman, 1985) can be generalized as a global chemical phenomenon (Molina, 1974) (UNEP, 2000). It is more
likely that the unique and peculiar changes in atmospheric ozone observed at AMS and HLB reflect changes in the ability of atmospheric circulations to transport ozone from the tropics to the South Pole (Kozubek, 2012) (Tegtmeier, 2008) (Weber, 2011).

SUMMARY#3: LATITUDINAL PATTERN OF OZONE DEPLETION

The left panel of SUMMARY#3 represents the southern hemisphere from AMS (-90o) to SMO (-14 latitude). The right panel represents the northern hemisphere from MLO (+19.5 latitude) to BRW (+71 latitude). The x-axis in each panel indicates the calendar months of the year from September = 1 to August = 12. The ordinate measures the average rate of change in total column ozone for each month among adjacent Lustra for all Lustra estimated using OLS regression of mean total column ozone against Lustrum number for each month. For example, in the left panel we see that in the month of September (x=1) ozone levels at HLB (shown in red) fell at an average rate of 15DU per Lustrum for the entire study period; and in the right panel we see that in the month of July (x=11) ozone levels at FBK (shown in orange) rose at an average rate of more than 2DU per Lustrum over the entire study period. The full study period is 50 years divided into 10 Lustra but it is abbreviated for some stations according to data availability. The concern about ozone depletion is derived from the finding by Farman et al in 1985 that ozone levels at HLB fell more than 100DU from the average value for October in 1957-1973 to the average value for October in 1980-1984. In comparison, changes of ±5DU from Lustrum to Lustrum seem inconsequential. In that light, and somewhat arbitrarily if we describe ±5DU per Lustrum as insignificant and perhaps representative of random natural variability, what we see in Figure 30 is that, except for the two Antarctica stations (AMS and HLB), no average change in monthly mean ozone from Lustrum to Lustrum falls outside this range. It is therefore not likely that the HLB data reported by Farman et al can be generalized globally. 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).

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1. ABSTRACT: Total column ozone data for each calendar month from twelve ground stations in a large range of latitudes are studied in a fifty-year sample period from 1966-2015. The study period is divided into ten Lustra (5-year periods). 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 -90 latitude to +71 latitude 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 that ozone depletion must be assessed across a greater range of latitudes and over a much longer period of time than what is found in Farman etal 1985 which serves as the only empirical basis for the ozone depletion hypothesis that led to the Montreal Protocol and the ascendance of the UN as a global environmental authority. It is far more likely that the historical decline of total column ozone in the South Pole during the months of October and November reported by Farman etal 1985 are related to natural cycles in atmospheric circulation patterns that transport ozone from the tropics to the South Pole. Data analysis over a wider range of latitudes does not show evidence of ozone decline. The data presented above imply that the Montreal Protocol is credited with solving a non-existent problem. 
2. BACKGROUND: 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 global 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). Since HHCs were non-toxic and, as of 1973, environmental science knew of no harmful effects of HHC, the fear of their accumulation in the atmosphere remained an academic curiosity. This situation changed in the following year with the publication of a paper by Mario Molina and Frank Rowland in which is contained the foundational theory of ozone depletion and the rationale for the Montreal Protocol’s plan to save the ozone layer (Molina, 1974). According to the Rowland-Molina theory of ozone depletion (RMTOD), the extreme volatility and chemical inertness of the HHCs ensure that there is no natural sink for these chemicals in the troposphere and that therefore once emitted they may remain in the atmosphere for 40 to 150 years and be transported by diffusion and atmospheric motion to the stratospheric ozone layer where they are subjected to solar radiation at frequencies that will cause them to dissociate into chlorine atoms and free radicals. Chlorine atoms can then act as a catalytic agent of ozone destruction in a chemical reaction cycle described in the paper and reproduced in Figure 1 (Molina, 1974). Ozone depletion poses a danger because the ozone layer protects life on the surface of the earth from the harmful effects of UVB radiation. The Rowland-Molina paper, the second key event that led to the Montreal Protocol, established that the atmospheric accumulation of HHC is not harmless and provided a theoretical framework that links HHC to ozone depletion.
3. FARMAN ETAL 1985: The third key event in the genesis of the Montreal Protocol was the paper by Farman, Gardiner, and Shanklin that is taken as empirical evidence for the kind of ozone depletion described by the RMTOD
   (Farman, 1985). The essential finding of the Farman paper is contained in the top frame of the paper’s Figure 1 which is reproduced here as Figure 2. Ignoring the very light lines in the top frame of Figure 2, we see two dark curves one darker than the other. The darker curve contains average daily values of total column ozone in Dobson units for the 5-year test period 1980-1984. The lighter curve shows daily averages for the 16-year reference period 1957-1973. The conclusions the authors draw from the graph are that (1) atmospheric ozone levels are lower in the test period than in the reference period and (2) that the difference is more dramatic in the two spring months of October and November than it is in the summer and fall. The difference and the seasonality of the difference between the two curves are interpreted by the authors in terms of the ozone depletion chemistry and their kinetics described by Molina and Rowland (Molina, 1974). The Farman paper was thus hailed as empirical evidence of RMTOD and the science of ozone depletion due to the atmospheric release of HHC appeared to be well established by these three key papers. First, atmospheric release of HHC caused them to accumulate in the atmosphere on a global scale because they are insoluble and chemically inert (Lovelock). Second, their long life and volatility ensure that they will end up in the stratosphere where HHC will be dissociated by radiation to release chlorine atoms which will act as catalytic agents of ozone depletion (Molina-Rowland). And third, empirical evidence validates the depletion of ozone and the role of HHC in the depletion mechanism (Farman et al). The Montreal Protocol was put in place on this basis. This study is an extension of a prior work that involved a survey of total column ozone data from ground stations (Munshi, Trends in atmospheric ozone, 2015). Its purpose is to evaluate the Farman findings across a range of latitudes and over a longer time period. The objective is to determine whether the findings by Farman can be generalized globally in terms of the Rowland-Molina theory of chemical ozone depletion.
4. DATA AND METHOD:  Total column ozone (TCO) measurements made with Dobson spectrophotometers at ground stations are used in this study. Twelve stations are selected to represent a large range of latitudes. The selected stations, each identified with a three-character code, are listed in Figure 1. The location of these stations are described and identified with global coordinates. The twelve stations may be classified into five groups according to latitude as (1) high southern latitudes (90o south to 60o south with stations AMS and HLB), (2) mid- southern latitudes (60o south to 30o south with stations LDR and PTH), (3) tropical latitudes (30o south to 30o north with stations SMO and MLO), (4) mid- northern latitudes (30o north to 60o north with stations WAI, BDR, CAR, and BIS), and (5) high northern latitudes (60o north to 90o north with stations FBK and BRW). The data are provided online by the NOAA (NOAA, 2015) (NOAA/ESRL, 2016) (NOAA/ESRL, 2016) and the British Antarctic Survey (BAS, 2016). Most stations provide daily mean values of total column ozone in Dobson units. The time span of the data ranges from 1957 to 2015. The first year of data available varies from station to station in the range of 1957 to 1987, and the last month from August 2013 to December 2015. Some months and some years in the span of measurements do not contain data for many of the stations. The core study period is somewhat arbitrarily defined as consisting of ten Lustra (5-year periods) from 1966 to 2015 (Table 2). The Farman paper may be cited as a precedence for the use of changes in 5-year means in the evaluation of long term trends. The period definitions are not precise for the first and last Lustra. The first Lustrum is longer than five years for some stations and shorter than five years for others. The last Lustrum is imprecise because of the variability in the last month of data availability. The calendar month sequence is arranged from September to August in the tables and charts presented to maintain seasonal integrity. The seasons are roughly defined as follows: September-November (northern autumn and southern spring), December-February (northern winter and southern summer), March-May (northern spring and southern autumn), and June-August (northern summer and southern winter). Daily and intraday ozone data are averaged into monthly means for each period. These monthly means are then used to study trends across the ten Lustra for each calendar month and also to examine the average seasonal cycle for each Lustrum. Trends in mean monthly ozone and seasonal cycles are compared to examine the differences among latitudes. These patterns are then used to compare and evaluate the chemical and transport theories for changes in atmospheric ozone. The chemical explanation of these changes rests on the destruction of ozone by chlorine atoms derived from HHC (Molina, 1974) while the transport theory describes them in terms of the Brewer-Dobson circulation (BDC) and polar vortices that transport ozone from the tropics where they are formed to the greater latitudes where they are more stable (Kozubek, 2012) (Butchart, 2014) (Tegtmeier, 2008) (Weber, 2011)

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REFERENCES

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ROWLAND-MOLINA OZONE DEPLETION CHEMISTRY

1. The ultraviolet spectrum in incident solar radiation comes in three frequency bands. The high energy band (200-240 nanometers in wavelength) and the medium energy band (240-300 nanometers in wavelength) are harmful to living matter and are absorbed in the ozone layer while the low energy band (300-480 nanometers in wavelength) reaches the earth’s surface and causes tanning. Ozone plays a role in the absorption of harmful UV radiation. It is both created and destroyed in the absorption process.
2. The high-energy band UV is absorbed by oxygen molecules. The energy absorbed causes the oxygen molecule to break apart into extremely reactive oxygen atoms. A subsequent chance collision of these particles with other oxygen molecules causes the formation of ozone. The ozone thus formed then absorbs the medium-energy UV band and disintegrates back into oxygen.The UV absorption process is a cyclical one that begins and ends with oxygen. Ozone is a transient intermediate product of this process.
3. The reason that there is any ozone accumulation at all in the stratosphere is that, of the three reactions, the second is the slowest. Sunset finds the stratosphere with an excess of single oxygen atoms still looking for a date with an oxygen molecule. Overnight, with no radiation to destroy their product, these particles build up an inventory of ozone whose destruction will begin anew at sunrise. There is therefore, a diurnal cycle in the ozone content of the stratosphere whose amplitude, incidentally, is of the same order of magnitude as reported ozone depletion that caused Montreal Protocol to be invoked.
4. A longer but irregular cyclical pattern in stratospheric ozone coincides with the sunspot cycle. The period is approximately eleven years. It has been as long as 17 and as short as 8 years. High-energy band UV increases by 6 to 10% during periods of high sunspot activity but the medium-energy UV emission is largely unaffected. Therefore, high sunspot activity favors ozone accumulation and low sunspot activity is coincident with ozone depletion.
5. A somewhat similar pattern exists in the case of polar ozone holes. The UV induced reactions described above occur only over the tropics where sunlight is direct. Ozone is formed over the equator and not over the poles. Equatorial ozone is distributed to the poles by the Brewer-Dobson Circulation (BDC). The shape and position of the BDC changes seasonally and also shifts over a longer time cycle. Therefore, the efficiency of the BDC in transporting ozone to the greater latitudes changes seasonally and also over longer time cycles. Brewer, A. W. “Evidence for a world circulation provided by the measurements of helium and water vapour distribution in the stratosphere.” Quarterly Journal of the Royal Meteorological Society 75.326 (1949): 351-363.
6. When the distribution of ozone is not efficient, localized “ozone depletion” appears to occur in the extreme latitudes in the form of what has come to be called an ozone hole. These holes come and go in natural cyclical changes and are not the creation of chemical ozone depletion.
7. Concurrent with the ozone hole scare, climate scientists report that the warming trend has weakened the Brewer Dobson circulation . This connection between climate and ozone appears to indicate that warming can create more frequent and larger ozone holes. Butchart, N., et al. “Simulations of anthropogenic change in the strength of the Brewer–Dobson circulation.” Climate Dynamics 27.7-8 (2006): 727-741. However, the effect of global warming or of changing atmospheric composition on the Brewer Dobson Circulation remains controversial. Garcia, Rolando R., and William J. Randel. “Acceleration of the Brewer–Dobson circulation due to increases in greenhouse gases.” Journal of the Atmospheric Sciences 65.8 (2008): 2731-2739.
8. The case against CFCs is that when they get to the stratosphere by diffusion, they absorb high-energy band UV and form unstable and reactive chlorine atoms. The chlorine atom particles then participate as catalytic agents to convert ozone back to oxygen. In other words they mediate the reaction between atomic oxygen particles and ozone. It is alleged that the destruction of ozone by this mechanism exposes the surface of the earth to dangerous levels of medium-band UV because there is not enough ozone in the stratosphere to absorb them. Although these reactions can be carried out in the chemistry lab, there are certain rate constraints that make them irrelevant in the stratosphere.
9. The air up there in the stratosphere is rather thin, containing less than one percent of the molecular density of air at sea level. It is not easy for a molecular particle in random thermal motion to find another particle to react with. Photochemical reactions occur instantaneously while those that require a collision of two particles take much longer. This difference in the reaction rate is the reason that ozone accumulates overnight and why there is an inventory of ozone in the ozone layer.
10. The atomic oxygen particles that react with oxygen molecules to form ozone could in theory react with an ozone molecule instead and cause its destruction or it could react with another atomic oxygen particle and form oxygen instead of ever forming any ozone. Some of the oxygen atoms do behave in this manner but these reactions proceed too slowly to be important to the chemistry of the stratosphere. The reason is that the stratospheric chemicals in question exist in minute quantities.
11. One in a million particles is an ozone molecule or an atomic oxygen particle and one in a billion is CFC or chlorine generated from CFC. The accidental collision between chlorine atoms and ozone molecules or between chlorine atoms and oxygen atoms are rarer than those between two oxygen atoms or that between an oxygen atom and an ozone molecule. Therefore the latter collisions are more important to ozone depletion than those mediated by chlorine.
12. Considering that more than 200,000 out of a million molecular particles in the stratosphere are oxygen molecules it is far more likely that charged oxygen atoms will collide with oxygen molecules rather than with each other or with ozone. Therefore ozone rather than oxygen is formed. Ozone formation is a rate phenomenon.
13. Since chlorine atoms are a thousand times rarer in the stratosphere than atomic oxygen particles, it is not likely that chlorine’s mediation in short circuiting ozone generation will occur sufficiently fast to be important. Nature already contains an ozone destruction mechanism that is more efficient than the CFC mechanism but ozone forms anyway.
14. However, the argument can be made that overnight after sunset, as charged oxygen atoms are used up the charged chlorine atoms take on a greater role in ozone destruction and also when these chemicals are distributed to the greater latitudes where sunlight is less direct and too weak to be ionizers of oxygen, the only ozone destruction chemistry left is that of charged chlorine atoms colliding with ozone. The  relative importance of these overnight and greater latitude reactions in making changes to latitudinally weighted mean global ozone can be checked by examining its overall long term trends as well as its trend profiles. These data are shown in the data analysis documents linked below. They do not show the ozone depletion described in the Montreal Protocol.