NATIONAL GEOGRAPHIC

CLIMATE 101: OZONE DEPLETION

The ozone layer helps to protect life from harmful ultraviolet radiation. Find out what caused the ozone hole, and how the 1989 Montreal Protocol sought to put an end to ozone depletion.

THIS POST IS A CRITICAL REVIEW OF A NATIONAL GEOGRAPHIC ARTICLE ON: CLIMATE 101: OZONE DEPLETION. LINK TO SOURCE: https://www.nationalgeographic.com/environment/global-warming/ozone-depletion/

PART-1: WHAT THE NATIONAL GEOGRAPHIC ARTICLE SAYS

CLIMATE 101: OZONE DEPLETION: The ozone layer helps to protect life from harmful ultraviolet radiation. Find out what caused the ozone hole, and how the 1989 Montreal Protocol sought to put an end to ozone depletion. BY CHRISTINA NUNEZ

Over the past 30 years humans have made progress in stopping damage to the ozone layer by curbing the use of certain chemicals. But more remains to be done to protect and restore the atmospheric shield that sits in the stratosphere about 9 to 18 miles (15 to 30 kilometers) above the Earth’s surface. Atmospheric ozone absorbs ultraviolet (UV) radiation from the sun, particularly harmful UVB-type rays. Exposure to UVB radiation is linked with increased risk of skin cancer and cataracts, as well as damage to plants and marine ecosystems. Atmospheric ozone is sometimes labeled as the “good” ozone, because of its protective role, and shouldn’t be confused with tropospheric, or ground-level, “bad” ozone, a key component of air pollution that is linked with respiratory disease.

Ozone (O3) is a highly reactive gas whose molecules are comprised of three oxygen atoms. Its concentration in the atmosphere naturally fluctuates depending on seasons and latitudes, but it generally was stable when global measurements began in 1957. Groundbreaking research in the 1970s and 1980s revealed signs of trouble.

In 1974, Mario Molina and Sherwood Rowland, two chemists at the University of California, Irvine, published an article in Nature detailing threats to the ozone layer from chlorofluorocarbon (CFC) gases. At the time, CFCs were commonly used in aerosol sprays and as coolants in many refrigerators. As they reach the stratosphere, the sun’s UV rays break CFCs down into substances that include chlorine. The groundbreaking research—for which they were awarded the 1995 Nobel Prize in chemistry—concluded that the atmosphere had a “finite capacity for absorbing chlorine” atoms in the stratosphere. One atom of chlorine can destroy more than 100,000 ozone molecules, according to the U.S. Environmental Protection Agency, eradicating ozone much more quickly than it can be replaced.

Molina and Rowland’s work received striking validation in 1985, when a team of English scientists found a hole in the ozone layer over Antarctica that was later linked to CFCs. The “hole” is actually an area of the stratosphere with extremely low concentrations of ozone that reoccurs every year at the beginning of the Southern Hemisphere spring (August to October). Spring brings sunlight, which releases chlorine into the stratospheric clouds.????

The ozone layer’s status today: Recognition of the harmful effects of CFCs and other ozone-depleting substances led to the Montreal Protocol on Substances That Deplete the Ozone Layer in 1987, a landmark agreement to phase out those substances that has been ratified by all 197 UN member countries. Without the pact, the U.S. would have seen an additional 280 million cases of skin cancer, 1.5 million skin cancer deaths, and 45 million cataracts—and the world would be at least 25 percent hotter.

More than 30 years after the Montreal Protocol, NASA scientists documented the first direct proof that Antarctic ozone is recovering because of the CFC phase-down: Ozone depletion in the region has declined 20 percent since 2005. And at the end of 2018, the United Nations confirmed in a scientific assessment that the ozone layer is recovering, projecting that it would heal completely in the (non-polar) Northern Hemisphere by the 2030s, followed by the Southern Hemisphere in the 2050s and polar regions by 2060. Monitoring of the ozone layer continues, and it’s finding that the recovery may not be as straightforward as hoped. A study in early 2018 found that ozone in the lower stratosphere unexpectedly and inexplicably has dropped since 1998, while another pointed to possible ongoing violations of the Montreal pact.

The world is not yet in the clear when it comes to harmful gases from coolants. Some hydrochlorofluorocarbons (HCFCs), transitional substitutes that are less damaging but still harmful to ozone, are still in use. Developing countries need funding from the Montreal Protocol’s Multilateral Fund to eliminate the most widely used of these, the refrigerant R-22. The next generation of coolants, hydrofluorocarbons (HFCs), do not deplete ozone, but they are powerful greenhouse gases that trap heat, contributing to climate change.

Though HFCs represent a small fraction of emissions compared with carbon dioxide and other greenhouse gases, their planet-warming effect prompted an addition to the Montreal Protocol, the Kigali Amendment, in 2016. The amendment, which came into force in January 2019, aims to slash the use of HFCs by more than 80 percent over the next three decades. In the meantime, companies and scientists are working on climate-friendly alternatives, including new coolants and technologies that reduce or eliminate dependence on chemicals.

PART-2: HISTORICAL BACKGROUND

1. The history of the ozone depletion issue presented here begins with a theory of ozone depletion by CFCs proposed by Rowland and Molina in 1974. Significant earlier events in this issue are missed in the presentation above are provided below. A more complete history is provided below.
2. The ozone story goes back to the 1960s when there was a plan to develop high altitude supersonic airliners. The high cruising altitude of the SST raised alarms that SSTs would cause ozone depletion. The alarm related to chemicals and aerosols in SST exhaust with a forecast of 40,000 additional cases of skin cancer every year in the USA alone.
3. In 1971 a theory was proposed that Nitric oxide (NOx) in the SST jet exhaust will cause ozone depletion because NOx acts as a catalyst to destroy ozone. The forecast said that there will be a 50% ozone depletion and a worldwide epidemic of skin cancer. Animals that venture out during daylight will become blinded by UV radiation. Ozone science deniers pointed out that the ozone had survived the NOx in the fireball of open air nuclear tests, but by 1972, the ozone depletion activism against the SST had won and the SST program died because we were too frightened by the ozone depletion scare.
4. In 1973 Ozone depletion scientists turned their attention to the proposed Space Shuttle program. The shuttle design included two solid fuel rockets that emit hydrogen chloride (HCl) which the scientists said would cause ozone depletion. The space shuttle miraculously survived the 1973 scare but the ozone depletion game was now in full gear, having tasted the power of being able to inflict debilitating fear of ozone depletion.
5. 1973: James Lovelock: In a now famous paper {Lovelock, Maggs, and Wade 1973}, environmentalist James Lovelock presented the discovery that air samples above the Atlantic ocean far from human habitation contained measurable quantities of HFC. This was the first of three key events that led to the Montreal Protocol and its worldwide ban on the production, sale, and atmospheric release of HFC and the rise of the UN as a global environmental regulator. This significant event in the history of the ozone depletion story was missed by National Geographic. It is not possible to understand the context of the Rowland Molina theory of ozone depletion without the role of Lovelock.
6. 1973 Environmentalist James Lovelock studied the unrestricted release of halogenated hydrocarbons into the atmosphere from their use as aerosol dispensers, fumigants, pesticides, and refrigerants. {Halogenated hydrocarbons (HHC) are also described as HFC}. Lovelock was concerned that these chemicals were man-made and they did not otherwise occur in nature and that they were chemically inert and that therefore their atmospheric release could cause irreversible accumulation. Since HHCs were non-toxic and environmental science knew of no harmful effects of HHC, the environmental concern expressed in Lovelock etal 1973 about their accumulation in the atmosphere remained an academic curiosity.
7. 1974: Th e current theory of ozone depletion appeared in 1974 when Rowland and Molina studied the Lovelock finding. They reasoned that 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. The Rowland Molina Theory of Ozone Depletion (RMTOD) proposed that such ozone depletion by HHC poses a danger because the ozone layer protects life on the surface of the earth from the harmful effects of UVB radiation.
8. 1985: Farman etal 1985: The RMTOD remained a theory – a reasonable conjecture based on the Lovelock data – but without empirical evidence it had no connection with the real world. The empirical evidence came more than a decade later in the now famous Farman etal 1985 paper. They found that “the spring values of total ozone in Antarctica have now fallen considerably. The circulation in the lower stratosphere is apparently unchanged, and possible chemical causes must be considered. We suggest that the very low temperatures which prevail from midwinter until several weeks after the spring equinox make the Antarctic stratosphere uniquely sensitive to growth of inorganic chlorine primarily by the effect of this growth on the NO2/NO ratio. This, with the height distribution of UV irradiation peculiar to the polar stratosphere, could account for the O3 losses observed.
9. 1985: This paper was the third and final key event in the sequence Lovelock to RMTOD to Farman, that led to the Montreal Protocol. Farman’s finding of an extreme ozone depletion over a 6-year period above the South Pole (later described as an “Ozone Hole” by NASA) was thought to have established that the atmospheric accumulation of HHC found by Lovelock (1) is not harmless by given the RMTOD theoretical framework (2) that links HHC to ozone depletion and finally (3) with the theory validated by empirical evidence in Farman etal. It is the combination of these three events that led to the Montreal Protocol and not any one of them by itself.
10. 1987–MONTREAL PROTOCOL MEDIA HYPE: The media then stepped in with an intensive exercise in fear based activism to promote compliance with the Montreal Protocol. Here are some examples: March 10 1987: Skin cancer is increasing in the United States at a near epidemic rate, outstripping predictions made as recently as five years ago, a research physician testified Monday before a House panel examining threats to the Earth’s protective ozone layer. Malignant melanoma, the deadliest form of skin cancer, has increased 83 percent in the last seven years alone. Melanoma is increasing faster than any other cancer except lung cancer in women.: March 12, 1987 Consensus among scientists: Harmful UV radiation can cause monumental problems, including rampant skin cancer and eye cataracts, retarded crop growth, impairment of the human immune system and damaging radiation doses to all forms of life. Although many Americans and the people of other nations are still not listening or taking the ozone threat seriously, the Earth’s protective shield is getting thinner and developing mysterious holes. There is a growing consensus among scientists that ozone destruction is caused by the accumulation in the upper atmosphere of chlorofluorocarbons (CFCs), a class of industrial chemicals used for refrigerants, aerosols, insulation, foam packaging and other uses.:

PART-3: CRITICAL COMMENTARY

1. RELATED POST ON OZONE CHEMISTRY: https://tambonthongchai.com/2018/04/01/ozone-depletion-and-ozone-holes/ . Here we note as follows: (1) The Montreal Protocol contains the assumption that without human intervention the amount of ozone in the stratosphere is invariant and that a decline in ozone over time of any duration is an anomaly that requires an explanation in terms of human cause in the form of CFC. This assumption is false as there are natural variations in stratospheric ozone. (2) The Diurnal Cycle: Ozone absorbs harmful UV radiation. It is both created and destroyed in that process. 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. 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 is of the same order of magnitude as the ozone depletion observed by Farman that serves as empirical evidence for RMTOD and the Montreal Protocol. (3) The Long Cycle: A longer and irregular cyclical pattern in stratospheric ozone coincides with the sunspot cycle. The period is approximately 11 years but it can vary from 8 years to 17 years. High-energy band UV increases by 6% to 10% during periods of high sunspot activity but the medium-energy UV emission is unaffected. Therefore, high sunspot activity favors ozone accumulation and low sunspot activity is coincident with ozone depletion. (4) A same kind of natural variability exists in the case of polar ozone holes. The UV induced reactions of ozone creation and destruction described above occur only over the tropics where sunlight is direct and not at greater latitudes. The equatorial ozone is then distributed to the greater latitudes by the Brewer-Dobson Circulation (BDC). THE SHAPE AND LOCATION OF THE BREWER DOBSON CIRCULATION CHANGES SEASONALLY AND SHIFTS AT LONGER TIME SCALES. Therefore, the efficiency of the BDC in transporting ozone to the greater latitudes changes seasonally and also over longer time cycles. 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 and they do not serve as empirical evidence of the Roland Molina theory of ozone depletion by CFCs.

RELATED POST#1 ON LONG TERM TRENDS IN GLOBAL MEAN TOTAL COLUMN OZONE https://tambonthongchai.com/2020/09/30/ozone-depletion-part-1/ Mean global total ozone is estimated as the latitudinally weighted average of total ozone measured by the TOMS and OMI satellite mounted ozone measurement devices for the periods 1979-1992 and 2005-2015 respectively. The TOMS dataset shows an OLS depletion rate of 0.65 DU per year on average in mean monthly ozone from January 1979 to December 1992. The OMI dataset shows an OLS accretion rate of 0.5 DU per year on average in mean monthly ozone from January 2005 to December 2015. The conflicting and inconsequential OLS trends may be explained in terms of the random variability of nature. These findings are inconsistent with the Rowland-Molina theory of ozone depletion because the theory implies continued and dangerous depletion of total ozone on a global scale until the year 2040.

RELATED POST#2 ON LONG TERM TRENDS IN GLOBAL MEAN TOTAL COLUMN OZONE : https://tambonthongchai.com/2020/10/01/ozone-depletion-part-3/ Here we use ozone data from ground stations to carry out an empirical test of the RMTOD. Total column ozone (TCO) measurements made with Dobson spectrophotometers at twelve ground stations are used in this study. The stations are selected to represent a large range of latitudes with the latitudes classified into five groups as (1) high southern latitudes (90S to 60S), (2) mid- southern latitudes (60S to 30S), (3) Tropical (30S to 30N), (4) mid- northern latitudes (30N to 60N), and (5) high northern latitudes (60N to 90north). The data are provided by the NOAA and the BAS (British Antarctic Survey).

FINDING: The concern about ozone depletion is derived from the finding by Farman et al in 1985 that ozone levels at HLB fell by 6DU per year from the 1957-1973 average to the 1980-1984 average. The data presented below show that ozone depletion rates of 6DU/year and higher are seen only at the South Pole. Outside of the South Pole the mean ozone depletion rate is close to zero with an uncertainty range of +/- 1DU per year, a range perhaps indicative of random natural variability. It is therefore not likely that the HLB data reported by Farman et al can be generalized globally. Yet, it served as the sole basis of validating the Rowland Molina theory of ozone depletion. This event then gave rise to the ozone depletion alarm that in turn led to a global environmental role of the UN and the Montreal Protocol, and eventually an assumed authority of the UN over global environmentalism and the climate change alarmism of our time.

CONCLUSION: THE ROWLAND MOLINA THEORY OF OZONE DEPLETION B BASED ON THE LONG LIFE OF INERT HFC AND THE SPECULATION THAT BECAUSE THEY ARE LIGHT AND INERT THEY CAN END UP IN THE STRATOSPHERE AND THAT IF THEY DO UV RADIATION WILL CAUSE CHLORINE TO BREAK OFF THE HFC AND CATALIZE OZONE DESTRUCTION. ALTHOUGH THE LAST PART OF THIS SEQUENCE HAS BEEN TESTED IN THE LAB, NO EVIDENCE HAS EVER BEEN PRESENTED THAT HFC HAVE INDEED BEEN FOUND IN THE STRATOSPHERE. THE ONLY EVIDENCE TO SUPPORT RMTOD IS THE DEPLETION OF OZONE OVER THE SOUTH POLE OVER A 6-YEAR PERIOD. THIS EVIDENCE DOES NOT CONTAIN A SUFFICIENTLY LONG TIME SPAN OR A SUFFICIENT GEOGRAPHICAL EXTENT TO SERVE AS EVIDENCE OF A LONG TERM STEADY DECLINE IN GLOBAL MEAN TOTAL COLUMN OZONE. IN THE STUDIES PRESENTED ABOVE, NO LONG TERM DECLINE IS FOUND IN GLOBAL MEAN TOTAL COLUMN OZONE. THUS NO EMPIRICAL EVIDENCE IS FOUND TO SUPPORT THE ROWLAND MOLINA THEORY OF OZONE DEPLETION.