From Regulation to Results: Examining the Nexus of GDP , Energy Use, and Ozone‐Depleting Substances Emissions Post‐Montreal Protocol

The 1987 Montreal Protocol on Substances that Deplete the Ozone Layer is a landmark agreement that has successfully reduced the global production, consumption, and emissions of ozone-depleting substances (ODSs). ODSs are also greenhouse gases that contribute to the radiative forcing of climate change. Using historical ODSs emissions and scenarios of potential emissions, we show that the ODS contribution to radiative forcing most likely would have been much larger if the ODS link to stratospheric ozone depletion had not been recognized in 1974 and followed by a series of regulations. The climate protection already achieved by the Montreal Protocol alone is far larger than the reduction target of the first commitment period of the Kyoto Protocol. Additional climate benefits that are significant compared with the Kyoto Protocol reduction target could be achieved by actions under the Montreal Protocol, by managing the emissions of substitute fluorocarbon gases and/or implementing alternative gases with lower global warming potentials.

To celebrate its 150 anniversary, Nature collected 10 extraordinary papers published on Nature in November, 2019. One of the papers is on the discovery of the Antarctic ozone hole, which was published by three British scientists, Joe C. Farman, Brian G. Gardiner, and Jonathan D. Shanklin, in 1985. They first showed observational evidence that Antarctic stratospheric ozone experienced drastic decrease in the early 1980s, by contrasting to the relative steady state in the 1970s. They also suggested that the ozone hole is due to human-made chlorofluorocarbons (CFCs). Nature invited Susan Solomon, who made outstanding contributions to our understanding of the ozone hole, to comment on the paper. She pointed out that “The unexpected discovery of a hole in the atmospheric ozone layer over the Antarctic revolutionized science—and helped to establish one of the most successful global environmental policies of the twentieth century.” The observational evidence by Farman et al. greatly confirmed earlier theoretical works by P. Cruzen, M. Molina, and F. Rowland who first emphasized in the 1970s that anthropogenic emissions of nitrogen oxides and CFCs would damage the ozone layer. Their observational confirmation led to the winning of the Nobel Prize in Chemistry by Cruzen, Molina, and Rowland in 1995. The discovery of the ozone hole also led to great international actions in reducing CFCs emissions and protecting the ozone layer, which is crucially important for screening solar ultraviolet radiation for surface life. A series of conventions has been organized by the United Nations, and the most successful one is the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer. The Montreal Protocol and the succeeding amendments, adjustments, and decisions were subsequently negotiated to control the consumption and production of anthropogenic emissions of ozone-depleting substances (ODSs) and some hydrofluorocarbons (HFCs). Since then, ODSs emissions have been largely reduced and showed rapid decrease since the early 1990s. The global ozone layer and the ozone hole over Antarctic all have showed gradual increasing since the late 1990s. According to predictions of climate-chemistry models, the global total column ozone will return to its 1980 values by 2045 when ODSs decline to very low levels, and the Antarctic ozone hole will recover by 2060. The gradual recovery of the ozone hole, due to reducing anthropogenic emissions, from severe depletion also due to human emissions, is considered a successful story that human can protect their environment through self-efforts. It provides us with the confidence that we are able to reduce greenhouse gas emissions and to solve the problem of global greenhouse warming. In the present paper, we will first introduce the discovery of the Antarctic ozone hole by Farman et al. Then, we introduce the chemical mechanisms of the Chapman and the catalytic reactions that result in the formation of the ozone layer, and how anthropogenic perturbations caused the Antarctic ozone hole. We shall also introduce the actions that was taken by international communities to protect the ozone layer. In the final section, we point out the important implications of the discovery of the ozone hole.

Stratospheric ozone depletion in the Antarctic is well known to cause changes in Southern Hemisphere tropospheric climate; however, because of its smaller magnitude in the Arctic, the effects of stratospheric ozone depletion on Northern Hemisphere tropospheric climate are not as obvious or well understood. Recent research using both global climate models and observational data has determined that the impact of ozone depletion on ozone extremes can affect interannual variability in tropospheric circulation in the Northern Hemisphere in spring. To further this work, we use a coupled chemistry–climate model to examine the difference in high cloud between years with anomalously low and high Arctic stratospheric ozone concentrations. We find that low ozone extremes during the late twentieth century, when ozone-depleting substances (ODS) emissions are higher, are related to a decrease in upper tropospheric stability and an increase in high cloud fraction, which may contribute to enhanced Arctic surface warming in spring through a positive longwave cloud radiative effect. A better understanding of how Arctic climate is affected by ODS emissions, ozone depletion, and ozone extremes will lead to improved predictions of Arctic climate and its associated feedbacks with atmospheric fields as ozone levels recover.

The ozone layer depletion and its recovery, as well as the climate influence of ozone-depleting substances (ODSs) and their substitutes that influence climate, are of interest to both the scientific community and the public. Here we report on the emissions of ODSs and their substitute from China, which is currently the largest consumer (and emitter) of these substances. We provide, for the first time, comprehensive information on ODSs and replacement hydrofluorocarbon (HFC) emissions in China starting from 1980 based on reported production and usage. We also assess the impacts (and costs) of controls on ODS consumption and emissions on the ozone layer (in terms of CFC-11-equivalent) and climate (in CO2-equivalent). In addition, we show that while China's future ODS emissions are likely to be defined as long as there is full compliance with the Montreal Protocol; its HFC emissions through 2050 are very uncertain. Our findings imply that HFC controls over the next decades that are more stringent than those under the Kigali Amendment to the Montreal Protocol would be beneficial in mitigating global climate change.

<p>Stratospheric ozone depletion in the Antarctic is well known to cause changes in Southern Hemisphere tropospheric climate; however, because of its smaller magnitude in the Arctic, the effects of stratospheric ozone depletion on Northern Hemisphere tropospheric climate are not as obvious or well understood. Recent research using both global climate models and observational data has determined that the impact of ozone depletion on ozone extremes can affect interannual variability in tropospheric circulation in the Northern Hemisphere in spring. To further this work, we use a coupled chemistry–climate model to examine the difference in high cloud between years with anomalously low and high Arctic stratospheric ozone concentrations. We find that low ozone extremes during the late twentieth century, when ozone-depleting substances (ODS) emissions are higher, are related to a decrease in upper tropospheric stability and an increase in high cloud fraction, which may contribute to enhanced Arctic surface warming in spring through a positive longwave cloud radiative effect. A better understanding of how Arctic climate is affected by ODS emissions, ozone depletion, and ozone extremes will lead to improved predictions of Arctic climate and its associated feedbacks with atmospheric fields as ozone levels recover.</p>

Stratospheric ozone depletion, first observed in the 1980s, has been caused by the increased production and use of substances such as chlorofluorocarbons (CFCs), halons and other chlorine-containing and bromine-containing compounds, collectively termed ozone-depleting substances (ODSs). Following controls on the production of major, long-lived ODSs by the Montreal Protocol, the ozone layer is now showing initial signs of recovery and is anticipated to return to pre-depletion levels in the mid-to-late twenty-first century, likely 2050–2060. These return dates assume widespread compliance with the Montreal Protocol and, thereby, continued reductions in ODS emissions. However, recent observations reveal increasing emissions of some controlled (for example, CFC-11, as in eastern China) and uncontrolled substances (for example, very short-lived substances (VSLSs)). Indeed, the emissions of a number of uncontrolled VSLSs are adding significant amounts of ozone-depleting chlorine to the atmosphere. In this Review, we discuss recent emissions of both long-lived ODSs and halogenated VSLSs, and how these might lead to a delay in ozone recovery. Continued improvements in observational tools and modelling approaches are needed to assess these emerging challenges to a timely recovery of the ozone layer.

Historical trend of ozone-depleting substances and hydrofluorocarbon concentrations during 2004–2020 derived from satellite observations and estimates for global emissions

Few estimation methods were discussed to handle the missing data problem in the panel data models. However, in the panel vector autoregressive (PVAR) model, there is no estimator to handle this problem. The traditional treatment in the case of incomplete data is to use the generalized method of moment (GMM) estimation based on only available data without imputation of the missing data. Therefore, this paper introduces a new GMM estimation for the PVAR model in case of incomplete data based on the mean imputation. Moreover, we make a Monte Carlo simulation study to study the efficiency of the proposed estimator. We compare between two GMM estimators based on the mean squared error (MSE) and relative bias (RB) criteria. The first is the GMM estimation based on the list-wise (LW) and the second is the GMM estimation using the mean imputation (MI) at multi-missing levels. The results showed that the MI estimator provides more efficiency than the LW estimator.

It is now recognized and confirmed that the ozone layer shields the biosphere from dangerous solar UV radiation and is also important for the global atmosphere and climate. The observed massive ozone depletion forced the introduction of limitations on the production of halogen-containing ozone-depleting substances (hODS) by the Montreal Protocol and its Amendments and adjustments (MPA). Further research was aimed at analyzing the role played by the Montreal Protocol to increase public awareness of its necessity. In this study, we evaluate the benefits of the Montreal Protocol on climate and ozone evolution using the Earth system model (ESM) SOCOLv4.0 which includes dynamic ocean, sea ice, interactive ozone, and stratospheric aerosol modules. Here, we analyze the results of the numerical experiments performed with and without limitations on the ozone-depleting substances emissions. In the experiments, we have used CMIP6 SSP2-4.5 and SSP5-8.5 scenarios for future forcing behavior. We confirm previous results regarding catastrophic ozone layer depletion in the case without MPA limitations. The climate effects of MPA consist of additional global mean warming by up to 2.5 K in 2100 caused by the direct radiative effect of the hODS. We also obtained dramatic changes in several essential climate variables such as regional surface air temperature, sea-ice cover, and precipitation fields. The warming rate without the MPA under the SSP2-4.5 scenario is comparable to the warming rate of the SSP5-8.5 scenario with MPA. Our research updates and complements previous modeling studies on the quantifying of MPA benefits for the terrestrial atmosphere and climate.

A thin layer of ozone in the atmosphere protects humans and terrestrial life from harmful ultraviolet radiation. The human creation and emission of ozone-depleting substances has thinned this layer so much that once a year a large localized region with almost no ozone appears over Antarctica. This is known as the hole in the ozone layer.

Abstract. The year 1980 has often been used as a benchmark for the return of Antarctic ozone to conditions assumed to be unaffected by emissions of ozone-depleting substances (ODSs), implying that anthropogenic ozone depletion in Antarctica started around 1980. Here, the extent of anthropogenically driven Antarctic ozone depletion prior to 1980 is examined using output from transient chemistry–climate model (CCM) simulations from 1960 to 2000 with prescribed changes of ozone-depleting substance concentrations in conjunction with observations. A regression model is used to attribute CCM modelled and observed changes in Antarctic total column ozone to halogen-driven chemistry prior to 1980. Wintertime Antarctic ozone is strongly affected by dynamical processes that vary in amplitude from year to year and from model to model. However, when the dynamical and chemical impacts on ozone are separated, all models consistently show a long-term, halogen-induced negative trend in Antarctic ozone from 1960 to 1980. The anthropogenically driven ozone loss from 1960 to 1980 ranges between 26.4 ± 3.4 and 49.8 ± 6.2 % of the total anthropogenic ozone depletion from 1960 to 2000. An even stronger ozone decline of 56.4 ± 6.8 % was estimated from ozone observations. This analysis of the observations and simulations from 17 CCMs clarifies that while the return of Antarctic ozone to 1980 values remains a valid milestone, achieving that milestone is not indicative of full recovery of the Antarctic ozone layer from the effects of ODSs.

Abstract. This study provides observation-based national estimates of CFC-11, CFC-12, CFC-113, and 1,1,1-trichloroethane emissions for the United States (US) and United Kingdom (UK) from municipal solid waste (MSW) landfills. The scarcity of national estimates has lead to the assumption that a significant fraction of the lingering ozone-depleting substance (ODS) emissions, which have been detected in industrialized countries, could be emitted from landfills. Spatial coverage was achieved through sampling at seven landfills in Massachusetts and through data provided by nine UK landfills. Linear least square regressions of recovered ODS vs. CH4 were used in combination with national estimates of landfill CH4 emissions to estimate 2006 national US and UK ODS landfill emissions. The ODS landfill emission estimates were then compared to recent estimates of total US and UK ODS emissions. US ODS landfill emissions are 0.4%–1% (0.006–0.09 Gg/year) of total US emissions. UK ODS landfill emission estimates are 1% (0.008 Gg/year) and 6% (0.03 Gg/year) of total UK CFC-11 and CFC-12 emissions, respectively. This indicates that landfills are only a minor source of lingering ODS emissions in the US, but may be more significant for CFC-12 emissions in the UK. The implication is that the majority of current ODS emissions in industrialized countries is likely coming from equipment still in use.

The 1987 Montreal Protocol to the Vienna Convention is the only Protocol to date adopted under the ozone layer treaty regime. The Montreal Protocol sets forth specific legal obligations, including limitations and reductions on the calculated levels of consumption and production of certain controlled ozone-depleting substances. Its negotiation and conclusion, shortly after the 1985 Vienna Convention, were prompted by new scientific evidence indicating that emissions of certain substances were significantly depleting and modifying the ozone layer and would have potential climatic effects (Preamble). The absence of scientific evidence that actual harm was occurring required the international community to take ‘precautionary measures to control equitably total global emissions’ of substances that deplete the ozone layer (Preamble).

It is now recognized and confirmed that the ozone layer shields the biosphere from dangerous solar UV radiation and is also important for the global atmosphere and climate. The observed massive ozone depletion forced the introduction of limitations on the production of halogen-containing ozone-depleting substances (hODS) by the Montreal Protocol and its Amendments (MPA). Further research was aimed at analyzing the role played by the Montreal Protocol to increase public awareness of its necessity. In this study, we evaluate the benefits of the Montreal Protocol on climate and ozone evolution using the Earth system model (ESM) SOCOLv4.0 which includes dynamic ocean, sea ice, interactive ozone, and stratospheric aerosol modules. Here, we analyze the results of the numerical experiments performed with and without limitations on the ozone-depleting substances emissions. In the experiments, we have used CMIP6 SSP2-4.5 and SSP5-8.5 scenarios for future forcing behavior. We confirm previous results relative to catastrophic ozone layer depletion in the case without MPA limitations. The climate effects of MPA consist of additional global mean warming by up to 2.5 K in 2100 caused by the direct radiative effect of the hODS. We also obtained dramatic changes in several essential climate variables such as regional surface air temperature, sea-ice cover, and precipitation fields. Our research updates and complements previous modeling studies on the quantification of MPA benefits for the terrestrial atmosphere and climate.

It is now recognized and confirmed that the ozone layer shields the biosphere from dangerous solar UV radiation and is also important for the global atmosphere and climate. The observed massive ozone depletion forced the introduction of limitations on the production of halogen-containing ozone-depleting substances (hODS) by the Montreal Protocol and its Amendments (MPA). Further research was aimed at analyzing the role played by the Montreal Protocol to increase public awareness of its necessity. In this study, we evaluate the benefits of the Montreal Protocol on climate and ozone evolution using the Earth system model (ESM) SOCOLv4.0 which includes dynamic ocean, sea ice, interactive ozone, and stratospheric aerosol modules. Here, we analyze the results of the numerical experiments performed with and without limitations on the ozone-depleting substances emissions. In the experiments, we have used CMIP6 SSP2-4.5 and SSP5-8.5 scenarios for future forcing behavior. We confirm previous results relative to catastrophic ozone layer depletion in the case without MPA limitations. The climate effects of MPA consist of additional global mean warming by up to 2.5 K in 2100 caused by the direct radiative effect of the hODS. We also obtained dramatic changes in several essential climate variables such as regional surface air temperature, sea-ice cover, and precipitation fields. Our research updates and complements previous modeling studies on the quantification of MPA benefits for the terrestrial atmosphere and climate.