Ozone depletion and climate change

Ozone depletion and climate change, or Ozone hole global warming in more popular terms, are environmental challenges whose connections have been explored and which have been compared and contrasted, for example in terms of global regulation, in various studies and books.

There is widespread scientific interest in better regulation of climate change, ozone depletion and air pollution, as in general the human relationship with the biosphere is deemed of major historiographical and political significance.^[1] Already by 1994 the legal debates about respective regulation regimes on climate change, ozone depletion and air pollution were being dubbed "monumental" and a combined synopsis provided.^[2]

There are some parallels between atmospheric chemistry and anthropogenic emissions in the discussions which have taken place and the regulatory attempts which have been made. Most important is that the gases causing both problems have long lifetimes after emission to the atmosphere, thus causing problems that are difficult to reverse. However, the Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol that amended it are seen as success stories, while the Kyoto Protocol on anthropogenic climate change has largely failed. Currently, efforts are being undertaken to assess the reasons and to use synergies, for example with regard to data reporting and policy design and further exchanging of information.^[3] While the general public tends to see global warming as a subset of ozone depletion, in fact ozone and chemicals such as chlorofluorocarbons (CFCs) and other halocarbons, which are held responsible for ozone depletion, are important greenhouse gases. Furthermore, natural levels of ozone in both the stratosphere and troposphere have a warming effect.^{[citation needed]}

There are various ways in which ozone depletion and climate change are interconnected, but ozone depletion is not a primary cause of climate change.

The Earth's atmospheric ozone has two effects on the Earth's temperature balance. Firstly, it absorbs solar ultraviolet radiation, leading to the heating of the stratosphere. Secondly, it also traps heat in the troposphere by absorbing infrared radiation emitted by the Earth's surface. Consequently, the impact of changes in ozone concentrations on climate depends on the altitude at which these changes occur. Human-produced chlorine- and bromine-containing gases, which cause major ozone losses in the lower stratosphere, have a cooling effect on the Earth's surface. In contrast, ozone increases in the troposphere caused by surface-pollution gases, contribute to the "greenhouse" effect and have a warming effect on the Earth's surface.

Policy approach

There are both links and major differences between ozone depletion and global warming and the way the two challenges have been handled. While in the case of atmospheric ozone depletion, in a situation of high uncertainty and against strong resistance, climate change regulation attempts at the international level such as the Kyoto Protocol have failed to reduce global emissions.[4]^[5] The Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol were both originally signed by only some member states of the United Nations (43 nations in the case of the Montreal Protocol in 1986) while Kyoto attempted to create a worldwide agreement from scratch. Expert consensus concerning CFCs in the form of the Scientific Assessment of Ozone Depletion was reached long after the first regulatory steps were taken, and as of 29 December 2012^[update], all countries in the United Nations plus the Cook Islands, the Holy See, Niue and the supranational European Union had ratified the original Montreal Protocol.^[6] These countries have also ratified the London, Copenhagen, and Montreal amendments to the Protocol. As of 15 April 2014^[update], the Beijing amendments had not been ratified by two state parties.^[7]

After the Vienna Convention, the halocarbon industry shifted its position and started supporting a protocol to limit CFC production. US manufacturer DuPont acted more quickly than their European counterparts.^[8] The EU shifted its position as well after Germany, which has a substantial chemical industry, gave up its defence of the CFC industry^[4] and started supporting more regulation. Government and industry in France and the UK had tried to defend their CFC-producing industries even after the Montreal Protocol had been signed.^[9]

The Vienna Convention was installed before a scientific consensus on the ozone hole was established.

Aant Elzinga wrote in 1996 about the consensus, that the Intergovernmental Panel on Climate Change has tried in the prior two reports a global consensus approach to climate action.^[10] Stephen Schneider and Paul N. Edwards, noted in 1997, that after the IPCC Second Assessment Report, the lobby group Global Climate Coalition and a few self-proclaimed “contrarian” scientists tried to discredit the conclusions of the report. They pointed out that the goal of the IPCC is to fairly represent the complete range of credible scientific opinion and if possible a consensus view.^[11]

In 2007,

A linear model of policy-making, based on a position that "the more knowledge we have, the better the political response will be", was not applied in the ozone case.[14] On the contrary, the CFC regulation process focused more on managing ignorance and uncertainties as a basis of political decision making, as the relationships between science, public (lack of) understanding and policy were better taken into account.^[5][12][15] In the meantime, such a player in the IPCC process as Michael Oppenheimer conceded some limitations of the IPCC consensus approach and asked for concurring, smaller assessments of special problems instead of repetitions of the large-scale approach every six years.^[16] It has become more important to provide a broader exploration of uncertainties.^[16] Others also see mixed blessings in the drive for consensus within the IPCC process and have asked for dissenting or minority positions to be included^[17] or for statements about uncertainties to be improved.^[18][19]

Public opinion

The two atmospheric problems have achieved significantly different levels of understanding by the public, including both the basic science and policy issues.^[15] People have limited scientific knowledge about global warming and tend to confuse it with^[20] or see it as a subset of the ozone hole.^[21] Not only on the policy level, ozone regulation fared much better than climate change in public opinion. Americans voluntarily switched away from aerosol sprays before the legislation was enforced, while climate change has failed in achieving a broader scientific comprehension and in raising comparable concern.^[15]

The metaphors used in the CFC discussion (ozone shield, ozone hole) resonated better with non-scientists and their concerns.

Sheldon Ungar Archived 2021-05-06 at the

The idea of rays penetrating a damaged “shield” meshes nicely with abiding and resonant cultural motifs, including “Hollywood affinities.” These range from the shields on the Starship Enterprise to Star Wars ... It is these pre-scientific bridging metaphors built around the penetration of a deteriorating shield that render the ozone problem relatively simple. That the ozone threat can be linked with Darth Vader means that it is encompassed in common sense understandings that are deeply ingrained and widely shared.^[15]

— Sheldon Ungar

The CFC regulation attempts at the end of the 1980s profited from those easy to grasp metaphors and the personal risk assumptions taken from them. The fate of celebrities like President Ronald Reagan, who had skin cancer removal from his nose in 1985 and 1987, was also of high importance.^[24] In case of the public opinion on climate change, no imminent danger is perceived.^[15]

Cost-benefit assessments and industry policy

The US chemical company DuPont had already lost some of their zeal in defending their products after a strategic manufacturing patent for Freon was set to expire in 1979. A citizen boycott of spray cans gained importance in parallel. Not by chance, the United States banned the use of CFCs in aerosol cans in 1978.^[25]

Government and industry in France and the UK tried to defend their CFC-producing industries even after the Montreal Protocol had been signed.^[9] The European Community rejected proposals to ban CFCs in aerosol sprays for a long time. The EU shifted its position after Germany, which also has a large chemical industry, gave up its defence of the CFC industry^[4] and started supporting moves towards regulation. After regulation was more and more enforced, DuPont acted faster than their European counterparts as they may have feared court action related to increased skin cancer, especially as the EPA had published a study in 1986 claiming that an additional 40 million cases and 800,000 cancer deaths were to be expected in the US in the next 88 years.^[8] The identification and marketing of a 100% ozone-safe hydrocarbon refrigerant called "Greenfreeze" by the NGO Greenpeace in the early 1990s had a rapid significant impact in major markets of Europe and Asia.^[26][27] The climate change protocols were less successful. In the case of Kyoto, then secretary of the environment Angela Merkel, prevented a possible failure by suggesting to use 1990 as starting date for emission reduction. In so far the demise of the Eastern European heavy industry allowed for a high commitment, but actual emissions kept on growing on a global scale.^[28]

Science background

There are various links between the two fields of human-atmospheric interaction. Policy experts have advocated for a closer linking of ozone protection and climate protection efforts.^[29][30]

The same CO
₂ radiative forcing that produces global warming is expected to cool the stratosphere.[39] This cooling, in turn, is expected to produce a relative increase in ozone (O
₃) depletion in the polar area and in the frequency of ozone holes.^[40] Conversely, ozone depletion represents a radiative forcing of the climate system^[41] of about −0.15 ± 0.10 watts per square metre (W/m²).^[34]

See also

• Climate change in the Arctic

References