Emissions Of Ozone-depleting Substances Research Articles

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

Global concentrations (or mole fractions) and emissions of ozone-depleting substances (ODSs) and their hydrofluorocarbon (HFCs) substitutes that are controlled by the Montreal Protocol and its Amendments and adjustments (MP) are of great interest to both the scientific community and public. Previous studies on global concentrations and emissions have mostly relied on ground-based observations. Here, we assess the global concentrations and emissions of eight MP controlled substances and methyl chloride from ACE-FTS (Atmospheric Chemistry Experiment high−resolution infrared Fourier transform spectrometer) satellite observations: CFC-11 (CFCl3), CFC-12 (CF2Cl2), CCl4, HCFC-22 (CHClF2), HCFC-141b (C2H3Cl2F), HCFC-142b (C2H3ClF2), HFC-23 (CHF3), HFC-134a (C2H2F4), and CH3Cl. Results show that the ACE-FTS satellite observations can be used to derive the concentrations and emissions of these ODSs, HFCs, and CH3Cl, as they are consistent with those derived from the ground-based observations. Our findings imply that the changes in the concentrations and emissions of the ODSs and HFCs closely match the regulatory status of the MP, and satellite observations can be used to monitor the past and future progress of the MP.

Measurements of CFC-11, CFC-12, and HCFC-22 total columns in the atmosphere at the St. Petersburg site in 2009–2019

Abstract. Monitoring atmospheric anthropogenic halocarbons plays an important role in tracking their atmospheric concentrations in accordance with international agreements on emissions of ozone-depleting substances and, thus, in estimating the ozone layer recovery. Within the Network for the Detection of Atmospheric Composition Change (NDACC), regular Fourier transform infrared (FTIR) measurements can provide information on the abundancies of halocarbons on a global scale. We improved retrieval strategies for deriving the CFC-11 (CCl3F), CFC-12 (CCl2F2), and HCFC-22 (CHClF2) atmospheric columns from IR solar radiation spectra measured by the Bruker IFS125HR spectrometer at the St. Petersburg site (Russia). We used the Tikhonov–Phillips regularization approach for solving the inverse problem with optimized values of regularization parameters. We tested the strategies developed by comparison of the FTIR measurements with independent data. The analysis of the time series of column-averaged dry air mole fractions (Xgas) measured in 2009–2019 gives mean values of 225 pptv (parts per trillion by volume; CFC-11), 493 pptv (CFC-12), and 238 pptv (HCFC-22). Trend values total −0.40 % yr−1 (CFC-11), −0.49 % yr−1 (CFC-12), and 2.12 % yr−1 (HCFC-22). We compared the means, trends, and seasonal variability in XCFC-11, XCFC-12, and XHCFC-22 to that of (1) near-ground volume mixing ratios (VMRs), measured at the observational site Mace Head, Ireland (GVMR), (2) the mean in the 8–12 km layer VMRs, measured by ACE-FTS and averaged over 55–65∘ N latitudes (SVMR), and (3) Xgas values of the Whole Atmosphere Community Climate Model (WACCM) for the St. Petersburg site (WXgas). In general, the comparison of Xgas with the independent data showed a good agreement of their means within the systematic errors of the measurements considered. The trends observed over the St. Petersburg site demonstrate the smaller decrease rates for XCFC-11 and XCFC-12 than that of the independent data and the same increase rate for XHCFC-22. As a whole, Xgas, SVMR, and WXgas showed qualitatively similar seasonal variations, while the GVMR variability is significantly less, and only the WXHCFC-22 variations are essentially smaller than that of XHCFC-22 and SVMRHCFC-22.

A decline in emissions of CFC-11 and related chemicals from eastern China.

Emissions of ozone-depleting substances, including trichlorofluoromethane (CFC-11), have decreased since the mid-1980s in response to the Montreal Protocol1,2. In recent years, an unexpected increase in CFC-11 emissions beginning in 2013 has been reported, with much of the global rise attributed to emissions from eastern China3,4. Here we use high-frequency atmospheric mole fraction observations from Gosan, South Korea and Hateruma, Japan, together with atmospheric chemical transport-model simulations, to investigate regional CFC-11 emissions from eastern China. We find that CFC-11 emissions returned to pre-2013 levels in 2019 (5.0±1.0 gigagramsper year in 2019, compared to 7.2±1.5gigagramsper year for 2008-2012, ±1standard deviation), decreasing by 10±3gigagramsper year since 2014-2017. Furthermore, we find that in this region, carbon tetrachloride (CCl4)and dichlorodifluoromethane(CFC-12) emissions-potentially associated with CFC-11 production-were higher than expected after 2013 and then declined one to two years before the CFC-11 emissions reduction. This suggests that CFC-11 production occurred in eastern China after the mandated global phase-out, and that there was a subsequent decline in production during 2017-2018. We estimate that the amount of the CFC-11 bank (the amount of CFC-11 produced, but not yet emitted) in eastern China is up to 112gigagrams larger in 2019 compared to pre-2013 levels, probably as a result of recent production. Nevertheless, it seems that any substantial delay in ozone-layer recovery has been avoided, perhaps owing to timely reporting3,4 and subsequent action by industry and government in China5,6.

Impacts of Stratospheric Ozone Extremes on Arctic High Cloud

AbstractStratospheric 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 discovery of the Antarctic ozone hole

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.

Renewed and emerging concerns over the production and emission of ozone-depleting substances

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.

Numerical Modeling of the Natural and Manmade Factors Influencing Past and Current Changes in Polar, Mid-Latitude and Tropical Ozone

A chemistry–climate model of the lower and middle atmosphere is used to compare the role of natural and anthropogenic factors in the observed variability of stratospheric ozone. Numerical experiments have been carried out on several scenarios of separate and combined effects of solar activity, stratospheric aerosol, sea surface temperature, greenhouse gases, and ozone-depleting substances emissions on ozone for the period from 1979 to 2020. Simulations for the past and present periods are compared to the results of ground-based and satellite observations. Estimates of observed trends in column total ozone for the entire period 1980–2018 and separately for the late twentieth and early twenty-first century are presented.

Changes in Emissions of Ozone-Depleting Substances from China Due to Implementation of the Montreal Protocol.

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.

An even longer road to recovery?

Atmosphere The ozone layer is on the path to recovery after concerted efforts to control the production of ozone-depleting substances under the Montreal Protocol. In the latter half of the 21st century, the ozone layer will be controlled mainly by atmospheric carbon dioxide concentrations. In a Perspective, Liang et al. explain that ozone layer recovery may slow down. This is because of incomplete compliance with the Montreal Protocol, rising emissions of ozone-depleting substances that are not controlled, and increasing emissions of natural ozone-destroying substances owing to climate change. Full recovery of the ozone layer to its 1980 state will require improved compliance with regulations and successful efforts to limit climate change. Science , this issue p. [1257][1] [1]: /lookup/doi/10.1126/science.aaq0145

Antarctic ozone depletion between 1960 and 1980 in observations and chemistry–climate model simulations

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.

The municipal solid waste landfill as a source of ozone-depleting substances in the United States and United Kingdom

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 importance of the Montreal Protocol in protecting climate

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.

Development of damage function for stratospheric ozone layer depletion

The purpose of our study was to develop damage functions due to ozone layer depletion, that related the emission of ozone depleting substances (ODS) to the damage of category endpoints. The ozone layer depletion causes many types of damage such as skin cancer, cataract, adverse effect to crop and plant growth. We assessed the increase of skin cancer incidence risk. The damage function have been developed with connecting the main processes on ozone depletion, emission of ODS, increase of tropospheric ODS, increase of stratospheric ODS, change of total ozone, change of B region ultra-violet (UV-B) at the surface, and the increase of skin cancer incidence. As the result, we could introduce damage functions of melanoma and non-melanoma skin cancer incidence for 13 species of ODSs and damage factors based on the disability-adjusted life years (DALYs). We also compared the DALYs value with the damage factors of Eco-indicator 99 (egalitarian and hierarchic value), and it was found that our result was several ten times as small except methyl bromide. Furthermore, a case study for refrigerator was performed and it showed that shifting to less ozone depleting substances reduced the risk of skin cancer incidence to one-fourteenth in DALYs.