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Goyal, Rishav, Matthew H. England, Alex Sen Gupta, and Martin Jucker. "Reduction in surface climate change achieved by the 1987 Montreal Protocol." Environmental Research Letters 14, no. 12 (2019): 124041. http://dx.doi.org/10.1088/1748-9326/ab4874.
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Previdi, Michael, and Lorenzo M. Polvani. "Impact of the Montreal Protocol on Antarctic Surface Mass Balance and Implications for Global Sea Level Rise." Journal of Climate 30, no. 18 (2017): 7247–53. http://dx.doi.org/10.1175/jcli-d-17-0027.1.
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Abstract The Montreal Protocol on Substances that Deplete the Ozone Layer, adopted in 1987, is an international treaty designed to protect the ozone layer by phasing out emissions of chlorofluorocarbons and other ozone-depleting substances (ODSs). A growing body of scientific evidence now suggests that the implementation of the Montreal Protocol will have significant effects on climate over the next several decades, both by enabling stratospheric ozone recovery and by decreasing atmospheric concentrations of ODSs, which are greenhouse gases. Here, using a state-of-the-art chemistry–climate model, the Community Earth System Model (Whole Atmosphere Community Climate Model) [CESM(WACCM)], it is shown that the Montreal Protocol, through its impact on atmospheric ODS concentrations, leads to a substantial decrease in Antarctic surface mass balance (SMB) over the period 2006–65 relative to a hypothetical “World Avoided” scenario in which the Montreal Protocol has not been implemented. This SMB decrease produces an additional 25 mm of global sea level rise (GSLR) by the year 2065 relative to the present day. It is found, however, that the additional GSLR resulting from the relative decrease in Antarctic SMB is more than offset by a reduction in ocean thermal expansion, leading to a net mitigation of future GSLR due to the Montreal Protocol.
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Egorova, T., E. Rozanov, J. Gröbner, M. Hauser, and W. Schmutz. "Montreal Protocol benefits simulated with CCM SOCOL." Atmospheric Chemistry and Physics Discussions 12, no. 7 (2012): 17001–30. http://dx.doi.org/10.5194/acpd-12-17001-2012.
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Abstract. Ozone depletion is caused by the anthropogenic increase of halogen containing species in the atmosphere, which results in the enhancement of the concentration of reactive chlorine and bromine in the stratosphere. To reduce the influence of anthropogenic ozone-depleting substances (ODS), the Montreal Protocol was agreed by Governments in 1987, with several Amendments adopted later. In order to assess the benefits of the Montreal Protocol and its Amendments (MPA) on ozone and UV radiation, two different runs of the chemistry-climate model (CCM) SOCOL have been carried out. The first run was driven by the emission of ozone depleting substances (ODS) prescribed according to the restrictions of the Montreal Protocol and all its Amendments. For the second run we allow the ODS to grow by 3% annually. We find that the MPA would have saved up to 80% of the global annual total ozone by the end of the 21st century. Our calculations also show substantial changes in surface temperature and precipitations that could occur in the world without MPA implementations. To illustrate the changes in UV radiation at the surface and to emphasize certain features which can only be seen for some particular regions if the influence of the cloud cover changes is accounted for, we calculate geographical distribution of the erythemally weighted irradiance (Eery). For the no Montreal Protocol simulation Eery increases by factor of 4 to 16 between the 1970s and 2100. For the scenario including the Montreal Protocol it is found that UV radiation starts to decrease in 2000, with continuous decline of 5% to 10% at middle latitudes in the Northern and Southern hemispheres.
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Egorova, T., E. Rozanov, J. Gröbner, M. Hauser, and W. Schmutz. "Montreal Protocol Benefits simulated with CCM SOCOL." Atmospheric Chemistry and Physics 13, no. 7 (2013): 3811–23. http://dx.doi.org/10.5194/acp-13-3811-2013.
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Abstract. Ozone depletion is caused by the anthropogenic increase of halogen-containing species in the atmosphere, which results in the enhancement of the concentration of reactive chlorine and bromine in the stratosphere. To reduce the influence of anthropogenic ozone-depleting substances (ODS), the Montreal Protocol was agreed by Governments in 1987, with several Amendments and Adjustments adopted later. In order to assess the benefits of the Montreal Protocol and its Amendments and Adjustments (MPA) on ozone and UV radiation, two different runs of the chemistry-climate model (CCM) SOCOL have been carried out. The first run was driven by the emission of ozone depleting substances (ODS) prescribed according to the restrictions of the MPA. For the second run we allow the ODS to grow by 3% annually. We find that the MPA would have saved up to 80% of the global annual total ozone by the end of the 21st century. Our calculations also show substantial changes of the stratospheric circulation pattern as well as in surface temperature and precipitations that could occur in the world without MPA implementations. To illustrate the changes in UV radiation at the surface and to emphasise certain features, which can only be seen for some particular regions if the influence of the cloud cover changes is accounted for, we calculate geographical distribution of the erythemally weighted irradiance (Eery). For the no Montreal Protocol simulation Eery increases by factor of 4 to 16 between the 1970s and 2100. For the scenario including the Montreal Protocol it is found that UV radiation starts to decrease in 2000, with continuous decline of 5% to 10% at middle latitudes in the both Northern and Southern Hemispheres.
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Wu, Yutian, Lorenzo M. Polvani, and Richard Seager. "The Importance of the Montreal Protocol in Protecting Earth’s Hydroclimate." Journal of Climate 26, no. 12 (2013): 4049–68. http://dx.doi.org/10.1175/jcli-d-12-00675.1.
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Abstract The 1987 Montreal Protocol regulating emissions of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODSs) was motivated primarily by the harm to human health and ecosystems arising from increased exposure to ultraviolet-B (UV-B) radiation associated with depletion of the ozone layer. It is now known that the Montreal Protocol has helped reduce radiative forcing of the climate system since CFCs are greenhouse gases (GHGs), and that ozone depletion (which is now on the verge of reversing) has been the dominant driver of atmospheric circulation changes in the Southern Hemisphere in the last half century. This paper demonstrates that the Montreal Protocol also significantly protects Earth’s hydroclimate. Using the Community Atmospheric Model, version 3 (CAM3), coupled to a simple mixed layer ocean, it is shown that in the “world avoided” (i.e., with CFC emissions not regulated), the subtropical dry zones would be substantially drier, and the middle- and high-latitude regions considerably wetter in the coming decade (2020–29) than in a world without ozone depletion. Surprisingly, these changes are very similar, in both pattern and magnitude, to those caused by projected increases in GHG concentrations over the same period. It is further shown that, by dynamical and thermodynamical mechanisms, both the stratospheric ozone depletion and increased CFCs contribute to these changes. The results herein imply that, as a consequence of the Montreal Protocol, changes in the hydrological cycle in the coming decade will be only half as strong as what they otherwise would be.
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Jovanovic, Djordje, Mario Lukinovic, and Zdravko Vitosevic. "Environment and health - thirty years of successful implementation of the Montreal protocol." Srpski arhiv za celokupno lekarstvo 147, no. 7-8 (2019): 492–96. http://dx.doi.org/10.2298/sarh190320043j.
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The Protocol on Ozone Depleting Substances (ODS) was signed in 1987 in Montreal. The main goal of the protocol is the international consensus and action regarding the drastic decrease of production and use of these substances, which results in increased UV radiation and consequently has a negative impact on human health and ecosystem. Besides the review of the ?legal and technical? implementation of the protocol until now and the withdrawal of ODS from use, this paper specially stresses the analysis of available research results regarding the positive impact on health, in correlation with the implementation of the Montreal Protocol (MP). Due to the results of the thirty-year-long use until now, the MP is referred to as one of the most successful international agreements, not only in the field of environmental protection, but also in the field of human health protection in relation to it, within a certain context. Besides the reduced negative impact of ultraviolet radiation (UV) to the ecosystem and people, we are also facing a reduced occurring trend of skin cancer, cataracts, and immune system diseases worldwide. Without the MP and its implementation, millions of people would have died because of UV radiation and the previously mentioned diseases. The treatment costs and the pressure to the health system in all the countries worldwide would have enormously increased because of that.
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Rosskopf, Erin N., Daniel O. Chellemi, Nancy Kokalis-Burelle, and Gregory T. Church. "Alternatives to Methyl Bromide: A Florida Perspective." Plant Health Progress 6, no. 1 (2005): 19. http://dx.doi.org/10.1094/php-2005-1027-01-rv.
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Methyl bromide is a soil fumigant used to control soilborne fungi, nematodes, and weeds in a wide range of agricultural, horticultural, and ornamental cropping systems. The Montreal Protocol of 1987 called for the phase-out of methyl bromide due to its ability to deplete atmospheric ozone, thus disrupting the UV protective ozone layer. This article reviews the current status of the on-going methyl bromide phase-out from the perspective of agriculture in Florida. Accepted for publication 27 September 2005. Published 27 October 2005.
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Mäder, J. A., J. Staehelin, T. Peter, D. Brunner, H. E. Rieder, and W. A. Stahel. "Evidence for the effectiveness of the Montreal Protocol to protect the ozone layer." Atmospheric Chemistry and Physics Discussions 10, no. 8 (2010): 19005–29. http://dx.doi.org/10.5194/acpd-10-19005-2010.
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Abstract. The release of man-made ozone depleting substances (ODS, including chlorofluorocarbons and halons) into the atmosphere has lead to a near-linear increase in stratospheric halogen loading since the early 1970s, which started to level off after the mid-1990s and then to decline, in response to the ban of many ODSs by the Montreal Protocol (1987). We developed a multiple linear regression model to test whether this has already a measurable effect on total ozone values observed by the global network of ground-based instruments. The model includes explanatory variables describing the influence of various modes of dynamical variability and of volcanic eruptions. In order to describe the anthropogenic influence a first version of the model contains a linear trend (LT) term, whereas a second version contains a term describing the evolution of equivalent effective stratospheric chlorine (EESC). By comparing the explained variance of these two models we evaluated which of the two terms better describes the observed ozone evolution. For a significant majority of the stations, the EESC proxy fits the long term ozone evolution better than the linear trend term. Therefore, we conclude that the Montreal Protocol has started to show measurable effects on the ozone layer about twenty years after it became legally binding.
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Mäder, J. A., J. Staehelin, T. Peter, D. Brunner, H. E. Rieder, and W. A. Stahel. "Evidence for the effectiveness of the Montreal Protocol to protect the ozone layer." Atmospheric Chemistry and Physics 10, no. 24 (2010): 12161–71. http://dx.doi.org/10.5194/acp-10-12161-2010.
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Abstract. The release of man-made ozone depleting substances (ODS, including chlorofluorocarbons and halons) into the atmosphere has led to a near-linear increase in stratospheric halogen loading since the early 1970s, which levelled off after the mid-1990s and then started to decline, in response to the ban of many ODS by the Montreal Protocol (1987). We developed a multiple linear regression model to test whether this already had a measurable effect on total ozone values observed by the global network of ground-based instruments. The model includes explanatory variables describing the influence of various modes of dynamical variability and of volcanic eruptions. In order to describe the anthropogenic influence a first version of the model contains a linear trend (LT) term, whereas a second version contains a term describing the evolution of Equivalent Effective Stratospheric Chlorine (EESC). By comparing the explained variance of these two model versions we evaluated, which of the two terms better describes the observed ozone evolution. For a significant majority of the stations, the EESC proxy fits the long term ozone evolution better than the linear trend term. Therefore, we conclude that the Montreal Protocol has started to show measurable effects on the ozone layer about twenty years after it became legally binding.
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Hearn, Brian. "CFC Regulations on Refrigeration Compressors Used in Environmental Test Chambers." Journal of the IEST 33, no. 6 (1990): 27–32. http://dx.doi.org/10.17764/jiet.2.33.6.c51368630463223v.
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The earlier discovery of the Antarctic ozone "hole" and current scientific evidence indicate that CFC emissions into the atmosphere deplete the ozone layer and present a long-term threat to the quality of human life. The items of most concern, from an ozone protection standpoint, are the long-lived, fully halogenated compounds—halons, CFCs, and chlorocarbons. Scientific information indicates that most, if not all, of the chlorine or bromine content of these compounds is transported to the stratosphere, where it has the potential to destroy ozone. Furthermore, these compounds remain in the atmosphere for an extended number of years, providing a significant background chlorine concentration. According to DuPont.2 an 85 percent reduction in global CFC emissions from 1986 levels is necessary just to maintain current atmospheric levels of chlorine from these compounds. The refrigerants used within environmental test chambers have been included among those identified as ozone depleting. Specifically, these are CFC-12 and CFC-502. The 1987 Montreal Protocol was revised in June of 1990. Further regulations on CFC products are contained within the Clean Air Bill that is being debated in the Fall of 1990. Restrictions pertaining to CFC-13 are being proposed.
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Srinivasan, Kandadai. "CFC Alternatives — A Fresh Look." Environmental Conservation 19, no. 4 (1992): 339–42. http://dx.doi.org/10.1017/s0376892900031465.
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This article examines, through a molecular perspective, the ‘ozone-friendly’ refrigerants R-134a and R-123 vis-à-vis R-12 and R-11, which are targeted to be phased out under the Montreal Protocol on Substances that Deplete the Ozone Layer, Final Act (1987). It appears that the molecular weight, size parameter, and dipole moment, of R-134a and R-123, may induce a pronounced effect on the chemical equilibrium of ice particles in the polar stratospheric clouds and subsequently influence the photochemical reactions therein.Non-polar, high-molecular-weight perfluoropropane (R-218), could be a better substitute for R-12, while R-134, which is a non-polar HFC of the ethane family, could also be a candidate although its molecular weight is lower than that of R-12. The search for a good substitute for R-11, however, must continue.
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Shreenaath, K. G. Sai, Jigar Golecha, L. Bruno Augustin, and M. Suresh. "Numerical Studies on R22 Refrigerant Compressor Using Environment Friendly Working Fluids." Applied Mechanics and Materials 493 (January 2014): 21–26. http://dx.doi.org/10.4028/www.scientific.net/amm.493.21.
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Vapour compression refrigeration is the most widely used method in domestic and commercial air conditioning and refrigeration systems. R22 (difluoromonochloromethane) is the most widely used HCFC (hydro chlorofluorocarbon) refrigerant in residential, commercial, industrial and transport cooling systems. Montreal protocol in 1987 banned the use of CFCs (chlorofluorocarbon) due to their adverse impact on the environment causing ozone depletion and global warming. HCFCs are also being phased out, though they are less destructive than CFCs. The present work explores compressor performance using alternate environment friendly working fluids so that R22 can be replaced in future. The refrigerants used for the studies are R134a (tetrafluoroethane), R290 (propane) and R600a (isobutane). Compressor performance is analysed by varying refrigerant mass flow rate, evaporator and condenser temperatures and studying their effect on compressor size, power and discharge temperature. A numerical simulation code has been developed in MATLAB using refrigerant properties taken from REFPROP.
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Tsvetkov, Oleg B., Igor V. Baranov, Yuriy A. Laptev, Alexander V. Sharkov, Vladimir V. Mitropov, and Alexey V. Fedorov. "Third Generation of Working Fluids for Advanced Refrigeration Heating and Power Generation Technologies." Key Engineering Materials 839 (April 2020): 51–56. http://dx.doi.org/10.4028/www.scientific.net/kem.839.51.
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Since the 1987 Montreal Protocol, chlorinated refrigerants (CFCs and HCFCs) have been pointed out as responsible for the destruction of the ozone layer. The chemical industry has realized suitable replacement for CFC-12 and for HCFC-22 e.g. HFC-134a, HFC-404A, HFC-410A, HFC-507. This generation of refrigerants developed by the chemical industry can be characterized by the no ozone depleting potential and long atmospheric lifetime resulting in global warming potential. The contribution of the HFCs to the global warming brings up to discussion whether the HFCs should be considered as a transitional substance. Historically the use of natural and ecologically safe refrigerants was a strategy to eliminate environmental problems and avoid uncertainties with synthetic replacement fluids. Since ammonia is toxic, carbon dioxide provide high pressure, and the hydrocarbons are flammable, the general conclusion is often drawn that natural fluids gave safety problems. This paper will describe the possibilities of application as working fluids in low-temperature engineering refrigeration, heat pumping and organic Rankine cycles of the hydrofluoroolefins (HFOs) as third generation of synthetic working fluids.
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Staehelin, Johannes, Pierre Viatte, Rene Stübi, Fiona Tummon, and Thomas Peter. "Stratospheric ozone measurements at Arosa (Switzerland): history and scientific relevance." Atmospheric Chemistry and Physics 18, no. 9 (2018): 6567–84. http://dx.doi.org/10.5194/acp-18-6567-2018.
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Abstract. Climatic Observatory (LKO) in Arosa (Switzerland), marking the beginning of the world's longest series of total (or column) ozone measurements. They were driven by the recognition that atmospheric ozone is important for human health, as well as by scientific curiosity about what was, at the time, an ill characterised atmospheric trace gas. From around the mid-1950s to the beginning of the 1970s studies of high atmosphere circulation patterns that could improve weather forecasting was justification for studying stratospheric ozone. In the mid-1970s, a paradigm shift occurred when it became clear that the damaging effects of anthropogenic ozone-depleting substances (ODSs), such as long-lived chlorofluorocarbons, needed to be documented. This justified continuing the ground-based measurements of stratospheric ozone. Levels of ODSs peaked around the mid-1990s as a result of a global environmental policy to protect the ozone layer, implemented through the 1987 Montreal Protocol and its subsequent amendments and adjustments. Consequently, chemical destruction of stratospheric ozone started to slow around the mid-1990s. To some extent, this raises the question as to whether continued ozone observation is indeed necessary. In the last decade there has been a tendency to reduce the costs associated with making ozone measurements globally including at Arosa. However, the large natural variability in ozone on diurnal, seasonal, and interannual scales complicates the capacity for demonstrating the success of the Montreal Protocol. Chemistry-climate models also predict a super-recovery of the ozone layer at mid-latitudes in the second half of this century, i.e. an increase of ozone concentrations beyond pre-1970 levels, as a consequence of ongoing climate change. These factors, and identifying potentially unexpected stratospheric responses to climate change, support the continued need to document stratospheric ozone changes. This is particularly valuable at the Arosa site, due to the unique length of the observational record. This paper presents the evolution of the ozone layer, the history of international ozone research, and discusses the justification for the measurements in the past, present and into future.
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Hu, Y., Y. Xia, and Q. Fu. "Tropospheric temperature response to stratospheric ozone recovery in the 21st century." Atmospheric Chemistry and Physics Discussions 10, no. 9 (2010): 22019–46. http://dx.doi.org/10.5194/acpd-10-22019-2010.
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Abstract. Observations show a stabilization or a weak increase of the stratospheric ozone layer since the late 1990s. Recent coupled chemistry-climate model simulations predicted that the stratospheric ozone layer will likely return to pre-1980 levels in the middle of the 21st century, as a results of the decline of ozone depleting substances under the 1987 Montreal Protocol. Since the ozone layer is an important component in determining stratospheric and tropospheric-surface energy balance, the recovery of the ozone layer may have significant impact on tropospheric-surface climate. Here, using multi-model ensemble results from both the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC-AR4) models and coupled chemistry-climate models, we show that as ozone recovery is considered, the troposphere is warmed more than that without considering ozone recovery, suggesting an enhancement of tropospheric warming due to ozone recovery. It is found that the enhanced tropospheric warming is mostly significant in the upper troposphere, with a global mean magnitude of ~0.41 K for 2001–2050. We also find that relatively large enhanced warming occurs in the extratropics and polar regions in summer and autumn in both hemispheres while the enhanced warming is stronger in the Northern Hemisphere than in the Southern Hemisphere. Enhanced warming is also found at the surface. The strongest enhancement of surface warming is located in the Arctic in boreal winter. The global annual mean enhancement of surface warming is about 0.16 K for 2001–2050.
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Ziemke, J. R., and S. Chandra. "Development of a climate record of tropospheric and stratospheric column ozone from satellite remote sensing: evidence of an early recovery of global stratospheric ozone." Atmospheric Chemistry and Physics 12, no. 13 (2012): 5737–53. http://dx.doi.org/10.5194/acp-12-5737-2012.
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Abstract. Ozone data beginning October 2004 from the Aura Ozone Monitoring Instrument (OMI) and Aura Microwave Limb Sounder (MLS) are used to evaluate the accuracy of the Cloud Slicing technique in effort to develop long data records of tropospheric and stratospheric ozone and for studying their long-term changes. Using this technique, we have produced a 32-yr (1979–2010) long record of tropospheric and stratospheric column ozone from the combined Total Ozone Mapping Spectrometer (TOMS) and OMI. Analyses of these time series suggest that the quasi-biennial oscillation (QBO) is the dominant source of inter-annual variability of stratospheric ozone and is clearest in the Southern Hemisphere during the Aura time record with related inter-annual changes of 30–40 Dobson Units. Tropospheric ozone for the long record also indicates a QBO signal in the tropics with peak-to-peak changes varying from 2 to 7 DU. The most important result from our study is that global stratospheric ozone indicates signature of a recovery occurring with ozone abundance now approaching the levels of year 1980 and earlier. The negative trends in stratospheric ozone in both hemispheres during the first 15 yr of the record are now positive over the last 15 yr and with nearly equal magnitudes. This turnaround in stratospheric ozone loss is occurring about 20 yr earlier than predicted by many chemistry climate models. This suggests that the Montreal Protocol which was first signed in 1987 as an international agreement to reduce ozone destroying substances is working well and perhaps better than anticipated.
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Fatkurrohman, Fatkurrohman. "INFLUENCE OF CONGRESS IN SUPPORTING ON ENVIRONMENTAL ISSUE IN RONALD REAGAN ADMINISTRATION." Jurnal Kawistara 8, no. 2 (2018): 123. http://dx.doi.org/10.22146/kawistara.30024.
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This research aims to analyze the influence of the United States Congress in influencing the policies of the Ronald Reagan administration in ratifying the Montreal Protocol. This research uses one of the models proposed by Graham T. Allison, a bureaucratic political model. This model is used to analyze the political process associated with the bargaining position and compromise between the actors involved in the governments of Ronald Reagan, Congress and DuPont (the company). To understand how these actors play their role in the domestic political process, researchers use qualitative research by collecting data in the form of books, journals and other documents. Explorative methods are used to explore related argumentative basics related to the political process that occurs between the three actors. The result of this study shows that Congress in the era of the Ronald Reagan administration, especially in the House of Representatives is more dominated than the Democratic Party than the Republicans, while in the Senate during 1981-1989, the Democratic Party was only dominant in 1987-1989. The important three things in this research that all actors obtained their interests. Firstly, it is DuPont Company. It received benefits from CFC (Chlorofluorocarbon) changing such as HFC (Hydrofluorocarbon), HC (Hydrocarbon), and PFC (Perfluorocarbon). Secondly, it is Congress Agency. It which was dominated by the members of Democratic Party that stressing on environmental issues could reach their political program such as environmental protection. Thirdly, it is the Executive Agency. It gained benefits in saving of budget $503 million up to $2,8 billion for treating many diseases such as cortical cataract cancer, decrease of body immunity, and environmental problems.
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Santos, Alexandre F., Pedro D. Gaspar, and Heraldo J. L. de Souza. "Ecoenergetic Comparison of HVAC Systems in Data Centers." Climate 9, no. 3 (2021): 42. http://dx.doi.org/10.3390/cli9030042.
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The topic of sustainability is of high importance today. Global efforts such as the Montreal Protocol (1987) and the Kigali Amendment (2016) are examples of joint work by countries to reduce environmental impacts and improve the level of the ozone layer, the choice of refrigerants and air conditioning systems, which is essential for this purpose. But what indicators are to be used to measure something so necessary? In this article, the types of air conditioning and GWP (Global Warming Potential) levels of equipment in the project phase were discussed, the issue of TEWI (Total Equivalent Warming Impact) that measures the direct and indirect environmental impacts of refrigeration equipment and air conditioning and a new methodology for the indicator was developed, the TEWI DC (DC is the direct application for Data Center), and using the formulas of this new adapted indicator it was demonstrated that the TEWI DC for Chicago (USA) was 2,784,102,640 kg CO2/10 years and Curitiba (Brazil) is 1,252,409,640 kg CO2/10 years. This difference in value corresponds to 222.30% higher annual emissions in Chicago than in Curitiba, showing that it is much more advantageous to install a Data Center in Curitiba than in Chicago in terms of environmental impact. The TEWI indicator provides a more holistic view, helping to combine energy and emissions into the same indicator.
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Babić, Ilija. "Životna sredina - opasnosti i pravna zaštita / Human Environment ‒ Risks and Legal Protection." Годишњак факултета правних наука - АПЕИРОН 6, no. 6 (2016): 48. http://dx.doi.org/10.7251/gfp1606048b.
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The most relevant factors that affect climate are astronomic cycles ant their effects on planet Earth and Earth’s orbit around the Sun. They have impact on the occurrence of glacial and interglacial periods at generally 100.000-year frequencies, which were affected by orbital shape variations and effects of greenhouse gases.The youngest geological epoch of the geological history of Earth is Holocene (started with warming) that began approximately 11.000 years BP. In that epoch, the shape of Earth’s orbit around the Sun was nearly circular, close to a perfect circle, and the seasonal contrast was less severe, due to decreased tilt of Earth’s axis from the plane of its orbit around the Sun. However, most scientists are arguing that the causes of rapid climate change are rooted in human activity, and not in its internal orbital variations. The main causes of global warming are increased level of carbon dioxide, but also of methane and chlorofluorocarbons in the atmosphere. These gases are responsible for the greenhouse effect, ozone layer depletion in stratosphere and rapid global warming. In order to set up the legal framework of environmental protection, the United Nations Conference on the Human Environment has adopted Stockholm Declaration in June 16, 1972. About twenty industrial states have ratified in 1987 the Montreal Protocol on Substances that Deplete the Ozone Layer, which has undergone many revisions by London Convention (1990), Copenhagen Accord (1992), Vienna Convention (1995), Kyoto Protocol (1997) and the Paris Agreement ‒ an international universal agreement on climate adopted at the 2015 Paris Climate Conference (COP21). Environmental protection in the European Union is provided for by its primary and secondary law, and the most EU environmental regulations were implemented in the Serbian legislation.
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Rowland, F. Sherwood. "Stratospheric ozone depletion." Philosophical Transactions of the Royal Society B: Biological Sciences 361, no. 1469 (2006): 769–90. http://dx.doi.org/10.1098/rstb.2005.1783.
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Solar ultraviolet radiation creates an ozone layer in the atmosphere which in turn completely absorbs the most energetic fraction of this radiation. This process both warms the air, creating the stratosphere between 15 and 50 km altitude, and protects the biological activities at the Earth's surface from this damaging radiation. In the last half-century, the chemical mechanisms operating within the ozone layer have been shown to include very efficient catalytic chain reactions involving the chemical species HO, HO 2 , NO, NO 2 , Cl and ClO. The NO X and ClO X chains involve the emission at Earth's surface of stable molecules in very low concentration (N 2 O, CCl 2 F 2 , CCl 3 F, etc.) which wander in the atmosphere for as long as a century before absorbing ultraviolet radiation and decomposing to create NO and Cl in the middle of the stratospheric ozone layer. The growing emissions of synthetic chlorofluorocarbon molecules cause a significant diminution in the ozone content of the stratosphere, with the result that more solar ultraviolet-B radiation (290–320 nm wavelength) reaches the surface. This ozone loss occurs in the temperate zone latitudes in all seasons, and especially drastically since the early 1980s in the south polar springtime—the ‘Antarctic ozone hole’. The chemical reactions causing this ozone depletion are primarily based on atomic Cl and ClO, the product of its reaction with ozone. The further manufacture of chlorofluorocarbons has been banned by the 1992 revisions of the 1987 Montreal Protocol of the United Nations. Atmospheric measurements have confirmed that the Protocol has been very successful in reducing further emissions of these molecules. Recovery of the stratosphere to the ozone conditions of the 1950s will occur slowly over the rest of the twenty-first century because of the long lifetime of the precursor molecules.
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Derwent, R. "The impact of the Montreal Protocol on halocarbon concentrations in northern hemisphere baseline and European air masses at Mace Head, Ireland over a ten year period from 1987–1996." Atmospheric Environment 32, no. 21 (1998): 3689–702. http://dx.doi.org/10.1016/s1352-2310(98)00092-2.
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Jones, A., J. Urban, D. P. Murtagh, et al. "Analysis of HCl and ClO time series in the upper stratosphere using satellite data sets." Atmospheric Chemistry and Physics Discussions 10, no. 4 (2010): 8623–55. http://dx.doi.org/10.5194/acpd-10-8623-2010.
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Abstract. Previous analyses of satellite and ground-based measurements of hydrogen chloride (HCl) and chlorine monoxide (ClO) have suggested that total inorganic chlorine in the upper stratosphere is on the decline. We create HCl and ClO time series using satellite data sets with the intension of extending them to beyond November 2008 so that an update can be made on the long term evolution of these two species. We use the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) data for the HCl analysis, and the Odin Sub-Millimetre Radiometer (SMR) and the Aura Microwave Limb Sounder (Aura-MLS) measurements for the study of ClO. Altitudes between 35 and 45 km and three latitude bands between 60° S–60° N for HCl, and 20° S–20° N for ClO are studied. HCl shows values to be reducing from peak 1997 values by −4.4% in the tropics and between −6.4% to −6.7% per decade in the mid-latitudes. Trend values are significantly different from a zero trend at the 2 sigma level. ClO is decreasing in the tropics by −7.1% ± 7.8%/decade based on measurements made from December 2001. As both of these species contribute most to the chlorine budget at these altitudes then HCl and ClO should decrease at similar rates. The results found here confirm how effective the 1987 Montreal protocol objectives and its amendments have been in reducing the total amount of inorganic chlorine.
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Jones, A., J. Urban, D. P. Murtagh, et al. "Analysis of HCl and ClO time series in the upper stratosphere using satellite data sets." Atmospheric Chemistry and Physics 11, no. 11 (2011): 5321–33. http://dx.doi.org/10.5194/acp-11-5321-2011.
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Abstract. Previous analyses of satellite and ground-based measurements of hydrogen chloride (HCl) and chlorine monoxide (ClO) have suggested that total inorganic chlorine in the upper stratosphere is on the decline. We create HCl and ClO time series using satellite data sets extended to November 2008, so that an update can be made on the long term evolution of these two species. We use the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) data for the HCl analysis, and the Odin Sub-Millimetre Radiometer (SMR) and the Aura Microwave Limb Sounder (Aura-MLS) measurements for the study of ClO. Altitudes between 35 and 45 km and two mid-latitude bands: 30° S–50° S and 30° N–50° N, for HCl, and 20° S–20° N for ClO and HCl are studied. ACE-FTS and HALOE HCl anomaly time series (with QBO and seasonal contributions removed) are combined to produce all instrument average time series, which show HCl to be reducing from peak 1997 values at a linear estimated rate of −5.1 % decade−1 in the Northern Hemisphere and −5.2 % decade−1 in the Southern Hemisphere, while the tropics show a linear trend of −5.8 % per decade (although we do not remove the QBO contribution there due to sparse data). Trend values are significantly different from a zero trend at the 2 sigma level. ClO is decreasing in the tropics by −7.1 % ± 7.8 % decade−1 based on measurements made from December 2001 to November 2008. The statistically significant downward trend found in HCl after 1997 and the apparent downward ClO trend since 2001 (although not statistically significant) confirm how effective the 1987 Montreal protocol objectives and its amendments have been in reducing the total amount of inorganic chlorine.
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Kohlhepp, R., R. Ruhnke, M. P. Chipperfield, et al. "Observed and simulated time evolution of HCl, ClONO2, and HF total column abundances." Atmospheric Chemistry and Physics 12, no. 7 (2012): 3527–56. http://dx.doi.org/10.5194/acp-12-3527-2012.
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Abstract. Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites belonging to the Network for the Detection of Atmospheric Composition Change (NDACC) and located between 80.05° N and 77.82° S. By providing such a near-global overview on ground-based measurements of the two major stratospheric chlorine reservoir species, HCl and ClONO2, the present study is able to confirm the decrease of the atmospheric inorganic chlorine abundance during the last few years. This decrease is expected following the 1987 Montreal Protocol and its amendments and adjustments, where restrictions and a subsequent phase-out of the prominent anthropogenic chlorine source gases (solvents, chlorofluorocarbons) were agreed upon to enable a stabilisation and recovery of the stratospheric ozone layer. The atmospheric fluorine content is expected to be influenced by the Montreal Protocol, too, because most of the banned anthropogenic gases also represent important fluorine sources. But many of the substitutes to the banned gases also contain fluorine so that the HF total column abundance is expected to have continued to increase during the last few years. The measurements are compared with calculations from five different models: the two-dimensional Bremen model, the two chemistry-transport models KASIMA and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. Thereby, the ability of the models to reproduce the absolute total column amounts, the seasonal cycles, and the temporal evolution found in the FTIR measurements is investigated and inter-compared. This is especially interesting because the models have different architectures. The overall agreement between the measurements and models for the total column abundances and the seasonal cycles is good. Linear trends of HCl, ClONO2, and HF are calculated from both measurement and model time series data, with a focus on the time range 2000–2009. This period is chosen because from most of the measurement sites taking part in this study, data are available during these years. The precision of the trends is estimated with the bootstrap resampling method. The sensitivity of the trend results with respect to the fitting function, the time of year chosen and time series length is investigated, as well as a bias due to the irregular sampling of the measurements. The measurements and model results investigated here agree qualitatively on a decrease of the chlorine species by around 1% yr−1. The models simulate an increase of HF of around 1% yr−1. This also agrees well with most of the measurements, but some of the FTIR series in the Northern Hemisphere show a stabilisation or even a decrease in the last few years. In general, for all three gases, the measured trends vary more strongly with latitude and hemisphere than the modelled trends. Relative to the FTIR measurements, the models tend to underestimate the decreasing chlorine trends and to overestimate the fluorine increase in the Northern Hemisphere. At most sites, the models simulate a stronger decrease of ClONO2 than of HCl. In the FTIR measurements, this difference between the trends of HCl and ClONO2 depends strongly on latitude, especially in the Northern Hemisphere.
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Kohlhepp, R., S. Barthlott, T. Blumenstock, et al. "Trends of HCl, ClONO <sub>2</sub> and HF column abundances from ground-based FTIR measurements in Kiruna (Sweden) in comparison with KASIMA model calculations." Atmospheric Chemistry and Physics Discussions 11, no. 1 (2011): 1489–510. http://dx.doi.org/10.5194/acpd-11-1489-2011.
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Abstract. Trends of hydrogen chloride (HCl), chlorine nitrate (ClONO2) and hydrogen fluoride (HF) column abundances above Kiruna (Northern Sweden, 67.84° N, 20.41° E) derived from nearly 14 years (1996–2009) of measurement and model data are presented. The measurements have been performed with a Bruker 120 HR (later Bruker 125 HR) Fourier transform infrared (FTIR) spectrometer and the model used was KASIMA (KArlsruhe SImulation model of the Middle Atmosphere). To calculate the long-term trends, a linear function combined with an annual cycle was fitted to the data using a least squares method. The precision of the resulting trends was estimated with the so-called bootstrap resampling method. The relative trends were calculated on the basis of the linear fit result on 1 January 2000, 12:00 UTC. For hydrogen fluoride, both model and measurements show a positive trend that seems to decrease in the last few years. This suggests a stabilisation of the HF total column abundance. For the summer data (August to November), the FTIR trend of (+1.25 ± 0.28)%/yr agrees within errors with the KASIMA one of (+1.55 ± 0.11)%/yr. The trends determined for HCl and ClONO2 are significantly negative over the time period considered here. This corresponds to the expectations because the emission of their precursors (chlorofluorocarbons and hydrochlorofluorocarbons) has been restricted in the Montreal Protocol in 1987 and its amendments and adjustments. The relative trend for ClONO2 from the FTIR measurements amounts to (−3.28 ± 0.56)%/yr and the one for HCl to (−0.81± 0.23)%/yr. KASIMA simulates a weaker decrease: For ClONO2, the result is (−0.90 ± 0.10)%/yr and for HCl (−0.17± 0.06)%/yr. Part of the difference between measurement and model data can be explained by sampling and the stronger annual cycle indicated by the measurements. There is a factor of about four between the trends of HCl and ClONO2 above Kiruna for both measurement and model data. The absolute values of ClONO2 and HF calculated by KASIMA agree quite well with the FTIR measurements while KASIMA tends to underestimate the HCl column abundances.
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Kohlhepp, R., S. Barthlott, T. Blumenstock, et al. "Trends of HCl, ClONO<sub>2</sub>, and HF column abundances from ground-based FTIR measurements in Kiruna (Sweden) in comparison with KASIMA model calculations." Atmospheric Chemistry and Physics 11, no. 10 (2011): 4669–77. http://dx.doi.org/10.5194/acp-11-4669-2011.
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Abstract. Trends of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) total column abundances above Kiruna (Northern Sweden, 67.84° N, 20.41° E) derived from nearly 14 years (1996–2009) of measurement and model data are presented. The measurements have been performed with a Bruker 120 HR (later Bruker 125 HR) Fourier transform infrared (FTIR) spectrometer and the chemistry-transport model (CTM) used was KASIMA (KArlsruhe SImulation model of the Middle Atmosphere). The total column abundances of ClONO2 and HF calculated by KASIMA agree quite well with the FTIR measurements while KASIMA tends to underestimate the HCl columns. To calculate the long-term trends, a linear function combined with an annual cycle was fitted to the data using a least squares method. The precision of the resulting trends was estimated with the bootstrap resampling method. For HF, both model and measurements show a positive trend that seems to decrease in the last few years. This suggests a stabilisation of the HF total column abundance. Between 1996 and 2009, KASIMA simulates an increase of (+1.51±0.07) %/yr which exceeds the FTIR result of (+0.65±0.25) %/yr. The trends determined for HCl and ClONO2 are significantly negative over the time period considered here. This is expected because the emission of their precursors (chlorofluorocarbons and hydrochlorofluorocarbons) has been restricted in the Montreal Protocol in 1987 and its amendments and adjustments. The trend for ClONO2 from the FTIR measurements amounts to (−3.28±0.56) %/yr and the one for HCl to (−0.81±0.23) %/yr. KASIMA simulates a weaker decrease: For ClONO2, the result is (−0.90±0.10) %/yr and for HCl (−0.17±0.06) %/yr. Part of the difference between measurement and model data can be explained by sampling and the stronger annual cycle indicated by the measurements. There is a factor of about four between the trends of HCl and ClONO2 above Kiruna for both measurement and model data.
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Kohlhepp, R., R. Ruhnke, M. P. Chipperfield, et al. "Observed and simulated time evolution of HCl, ClONO<sub>2</sub>, and HF total column abundances." Atmospheric Chemistry and Physics Discussions 11, no. 12 (2011): 32085–160. http://dx.doi.org/10.5194/acpd-11-32085-2011.
Full textAbstract:
Abstract. Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites belonging to the Network for the Detection of Atmospheric Composition Change (NDACC) and located between 80.05° N and 77.82° S. These measurements are compared with calculations from five different models: the two-dimensional Bremen model, the two chemistry-transport models KASIMA and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. The overall agreement between the measurements and models for the total column abundances and the seasonal cycles is good. Trends of HCl, ClONO2, and HF are calculated from both measurement and model time series data, with a focus on the time range 2000–2009. Their precision is estimated with the bootstrap resampling method. The sensitivity of the trend results with respect to the fitting function, the time of year chosen and time series length is investigated, as well as a bias due to the irregular sampling of the measurements. For the two chlorine species, a decrease is expected during this period because the emission of their prominent anthropogenic source gases (solvents, chlorofluorocarbons (CFCs)) was restricted by the Montreal Protocol 1987 and its amendments and adjustments. As most of the restricted source gases also contain fluorine, the HF total column abundance was also influenced by the above-mentioned regulations in the time period considered. The measurements and model results investigated here agree qualitatively on a decrease of the chlorine species by around −1 % yr−1. The models simulate an increase of HF of around +1 % yr−1. This also agrees well with most of the measurements, but some of the FTIR series in the Northern Hemisphere show a stabilisation or even a decrease in the last few years. In general, for all three gases, the measured trends vary more strongly with latitude and hemisphere than the modelled trends. Relative to the FTIR measurements, the models tend to underestimate the decreasing chlorine trends and to overestimate the fluorine increase in the Northern Hemisphere. At most sites, the models simulate a stronger decrease of ClONO2 than of HCl. In the FTIR measurements, this difference between the trends of HCl and ClONO2 depends strongly on latitude, especially in the Northern Hemisphere.
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Ball, William T., Justin Alsing, Johannes Staehelin, Sean M. Davis, Lucien Froidevaux, and Thomas Peter. "Stratospheric ozone trends for 1985–2018: sensitivity to recent large variability." Atmospheric Chemistry and Physics 19, no. 19 (2019): 12731–48. http://dx.doi.org/10.5194/acp-19-12731-2019.
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Abstract. The Montreal Protocol, and its subsequent amendments, has successfully prevented catastrophic losses of stratospheric ozone, and signs of recovery are now evident. Nevertheless, recent work has suggested that ozone in the lower stratosphere (< 24 km) continued to decline over the 1998–2016 period, offsetting recovery at higher altitudes and preventing a statistically significant increase in quasi-global (60∘ S–60∘ N) total column ozone. In 2017, a large lower stratospheric ozone resurgence over less than 12 months was estimated (using a chemistry transport model; CTM) to have offset the long-term decline in the quasi-global integrated lower stratospheric ozone column. Here, we extend the analysis of space-based ozone observations to December 2018 using the BASICSG ozone composite. We find that the observed 2017 resurgence was only around half that modelled by the CTM, was of comparable magnitude to other strong interannual changes in the past, and was restricted to Southern Hemisphere (SH) midlatitudes (60–30∘ S). In the SH midlatitude lower stratosphere, the data suggest that by the end of 2018 ozone is still likely lower than in 1998 (probability ∼80 %). In contrast, tropical and Northern Hemisphere (NH) ozone continue to display ongoing decreases, exceeding 90 % probability. Robust tropical (>95 %, 30∘ S–30∘ N) decreases dominate the quasi-global integrated decrease (99 % probability); the integrated tropical stratospheric column (1–100 hPa, 30∘ S–30∘ N) displays a significant overall ozone decrease, with 95 % probability. These decreases do not reveal an inefficacy of the Montreal Protocol; rather, they suggest that other effects are at work, mainly dynamical variability on long or short timescales, counteracting the positive effects of the Montreal Protocol on stratospheric ozone recovery. We demonstrate that large interannual midlatitude (30–60∘) variations, such as the 2017 resurgence, are driven by non-linear quasi-biennial oscillation (QBO) phase-dependent seasonal variability. However, this variability is not represented in current regression analyses. To understand if observed lower stratospheric ozone decreases are a transient or long-term phenomenon, progress needs to be made in accounting for this dynamically driven variability.
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Zhang, H., S. Wu, and Y. Wang. "Effects of stratospheric ozone recovery on tropospheric chemistry and air quality." Atmospheric Chemistry and Physics Discussions 13, no. 8 (2013): 21427–53. http://dx.doi.org/10.5194/acpd-13-21427-2013.
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Abstract. The stratospheric ozone has decreased greatly since 1980 due to ozone depleting substances (ODSs). As a result of the implementation of the Montreal Protocol and its amendments and adjustments, stratospheric ozone is expected to recover towards its pre-1980 level in the coming decades. We examine the implications of stratospheric ozone recovery for the tropospheric chemistry and ozone air quality with a global chemical transport model (GEOS-Chem). Significant decreases in surface ozone photolysis rates due to stratospheric ozone recovery are simulated. Increases in ozone lifetime by up to 7% are calculated in the troposphere. The global average OH decreases by 1.74% and the global burden of tropospheric ozone increases by 0.78%. The perturbations to tropospheirc ozone and surface ozone show large seasonal and spatial variations. General increases in surface ozone are calculated for each season, with increases by up to 5% for some regions.
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Keeble, James, N. Luke Abraham, Alexander T. Archibald, et al. "Modelling the potential impacts of the recent, unexpected increase in CFC-11 emissions on total column ozone recovery." Atmospheric Chemistry and Physics 20, no. 12 (2020): 7153–66. http://dx.doi.org/10.5194/acp-20-7153-2020.
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Abstract. The temporal evolution of the abundance of long-lived, anthropogenic chlorofluorocarbons in the atmosphere is a major factor in determining the timing of total column ozone (TCO) recovery. Recent observations have shown that the atmospheric mixing ratio of CFC-11 is not declining as rapidly as expected under full compliance with the Montreal Protocol and indicate a new source of CFC-11 emissions. In this study, the impact of a number of potential future CFC-11 emissions scenarios on the timing of the TCO return to the 1960–1980 mean (an important milestone on the road to recovery) is investigated using the Met Office's Unified Model (Hewitt et al., 2011) coupled with the United Kingdom Chemistry and Aerosol scheme (UM-UKCA). Key uncertainties related to this new CFC-11 source and their impact on the timing of the TCO return date are explored, including the duration of new CFC-11 production and emissions; the impact of any newly created CFC-11 bank; and the effects of co-production of CFC-12. Scenario-independent relationships are identified between cumulative CFC emissions and the timing of the TCO return date, which can be used to establish the impact of future CFC emissions pathways on ozone recovery in the real world. It is found that, for every 200 Gg Cl (∼258 Gg CFC-11) emitted, the timing of the global TCO return to 1960–1980 averaged values is delayed by ∼0.56 years. However, a marked hemispheric asymmetry in the latitudinal impacts of cumulative Cl emissions on the timing of the TCO return date is identified, with longer delays in the Southern Hemisphere than the Northern Hemisphere for the same emission. Together, these results indicate that, if rapid action is taken to curb recently identified CFC-11 production, then no significant delay in the timing of the TCO return to the 1960–1980 mean is expected, highlighting the importance of ongoing, long-term measurement efforts to inform the accountability phase of the Montreal Protocol. However, if the emissions are allowed to continue into the future and are associated with the creation of large banks, then significant delays in the timing of the TCO return date may occur.
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Fraser, Paul J., Bronwyn L. Dunse, Paul B. Krummel, et al. "Australian chlorofluorocarbon (CFC) emissions: 1960–2017." Environmental Chemistry 17, no. 8 (2020): 525. http://dx.doi.org/10.1071/en19322.
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Environmental contextChlorofluorocarbons (CFCs) are potent greenhouse and stratospheric ozone depleting trace gases. Their atmospheric concentrations are in decline, thanks to global production and consumption controls imposed by the Montreal Protocol. In recent years, the rates of decline of CFC atmospheric concentrations, especially for CFC-11 (CCl3F), are not as large as anticipated under the Protocol, resulting in renewed efforts to estimate CFC consumption and/or emissions to possibly identify new or poorly quantified sources. AbstractAustralian emissions of chlorofluorocarbons (CFCs) have been estimated from atmospheric CFC observations by both inverse modelling and interspecies correlation techniques, and from CFC production, import and consumption data compiled by industry and government. Australian and global CFC emissions show similar temporal behaviour, with emissions peaking in the late-1980s and then declining by ~10% per year through to the present. Australian CFC emissions since 1978 account for less than 1% of global emissions and therefore make a correspondingly small contribution to stratospheric ozone depletion. The current CFC emissions in Australia are likely from ‘banks’ of closed-cell foams, and refrigeration–air conditioning equipment now more than 20 years old. There is no evidence of renewed consumption or emissions of CFCs in Australia. The reduction in CFC emissions has made a significant contribution to reducing Australian greenhouse gas emissions.
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Rojasavastera, Rommanee, Sunee Bovonsunthonchai, Vimonwan Hiengkaew, and Vorapun Senanarong. "Action observation combined with gait training to improve gait and cognition in elderly with mild cognitive impairment A randomized controlled trial." Dementia & Neuropsychologia 14, no. 2 (2020): 118–27. http://dx.doi.org/10.1590/1980-57642020dn14-020004.
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Abstract. Owing to advancement of medical technology and current knowledge, the population has a longer life expectancy, leading to an increase in the proportion of elderly. Objective: The study aimed to investigate the effect of action observation (AO) combined with gait training on gait and cognition in elderly with mild cognitive impairment (MCI). Methods: Thirty-three participants were randomly allocated to action observation with gait training (AOGT), gait training (GT), and control (CT) groups. The AOGT and GT groups received a program of observation and gait training protocol with the same total duration of 65 min for 12 sessions. For the observation, the AGOT group watched a video of normal gait movement, while the GT group watched an abstract picture and the CT group received no training program. All participants were assessed for gait parameters during single- and dual-tasks using an electronic gait mat system and were assessed for cognitive level using the Montreal Cognitive Assessment (MoCA) at baseline, after training and at 1-month follow-up. Results: The results showed that the AOGT group had significant improvements in gait speeds during single- and dual-tasks, as well as better MoCA score, while the GT group had significant improvement only in gait speed. Conclusion: The adjunct treatment of AO with gait training provides greater benefits for both gait and cognitive performances in elderly with MCI.
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Pastukhova, A. S., N. E. Chubarova, Ye Yu Zhdanova, V. Ya Galin, and S. P. Smyshlyaev. "The forecast of erythemal UV irradiance over the territory of Northern Eurasia according to the INM-RSHU chemical-climate model." Известия Российской академии наук. Физика атмосферы и океана 55, no. 3 (2019): 20–28. http://dx.doi.org/10.31857/s0002-351555320-28.
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In this work, the impact of various factors on the total ozone column and erythemal UV radiation (Qery) in the territory of Northern Eurasia for the period from 1979 to 2059 based on the calculations of the chemical-climate model INM-RHSU is analyzed. The sensitivity of ozone recovery to the setting of different input data on sea surface temperature (SST) is estimated. Depending on the SST datasets, there are significant differences in ozone trends. A possible mechanism that explains the reasons for these differences is examined. The numerical experiment with the only change in ozone depleting substances according to Montreal protocol showed the ozone recovery and, as a result, Qery reduction, but this recovery is not linear. During the 2016-2020 period we estimated the 2-5% increase in Qery values relative to the baseline period (1979-1983) with about 6% maximum over Russian polar region. During the 2035-2039 period the Qery change against 1979-1983 period is about zero, during the 2055-2059 period we obtained the decrease of about 4-6% over Northern Asia and 6-8% over Northern Europe These changes corresponded to the noticeable boundary location shift of UV resources, which determine UV radiation impact on human health. The most significant changes will be observed in spring and summer: the UV deficiency zone will be expanded in the north and the UV excess zone over northern seas will be reduced in the south.
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Fraser, Paul J., Bronwyn L. Dunse, Alistair J. Manning, et al. "Australian carbon tetrachloride emissions in a global context." Environmental Chemistry 11, no. 1 (2014): 77. http://dx.doi.org/10.1071/en13171.
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Environmental context Carbon tetrachloride in the background atmosphere is a significant environmental concern, responsible for ~10% of observed stratospheric ozone depletion. Atmospheric concentrations of CCl4 are higher than expected from currently identified emission sources: largely residual emissions from production, transport and use. Additional sources are required to balance the expected atmospheric destruction of CCl4 and may contribute to a slower-than-expected recovery of the Antarctic ozone ‘hole’. Abstract Global (1978–2012) and Australian (1996–2011) carbon tetrachloride emissions are estimated from atmospheric observations of CCl4 using data from the Advanced Global Atmospheric Gases Experiment (AGAGE) global network, in particular from Cape Grim, Tasmania. Global and Australian emissions are in decline in response to Montreal Protocol restrictions on CCl4 production and consumption for dispersive uses in the developed and developing world. However, atmospheric data-derived emissions are significantly larger than ‘bottom-up’ estimates from direct and indirect CCl4 production, CCl4 transportation and use. Australian CCl4 emissions are not a result of these sources, and the identification of the origin of Australian emissions may provide a clue to the origin of some of these ‘missing’ global sources.
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Trudeau, Hélène, and Suzanne Lalonde. "La mise en oeuvre du Protocole de Kyoto au Canada : concertation ou coercition ?" Revue générale de droit 34, no. 1 (2014): 141–97. http://dx.doi.org/10.7202/1027237ar.
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L’intégration du Protocole de Kyoto au Canada suscite de vives tensions entre le gouvernement fédéral et les provinces, notamment en raison de l’incertitude qui entoure l’épineuse question du partage des compétences législatives pour assurer sa mise en œuvre. La lutte contre le réchauffement climatique global est-elle une matière de compétence fédérale ou une matière de compétence provinciale ? Devant l’opposition prévisible de certaines provinces à la mise en oeuvre unilatérale du Protocole de Kyoto par le gouvernement fédéral, il y a lieu d’envisager les deux voies possibles pour l’État canadien soucieux de respecter ses engagements internationaux en matière de diminution d’émissions de gaz à effet de serre. Ces deux voies sont celles de la concertation, option privilégiée jusqu’à maintenant, et celle de la coercition, qui surviendra en cas d’échec de la coopération, et qui pourra conduire à un arbitrage de la question constitutionnelle devant les tribunaux. Le présent texte explore d’abord l’avenue de la coopération fédérale-provinciale, en soulevant à la fois les possibilités et les limites qui la caractérisent. Sont ainsi présentées les techniques classiques de la réserve fédérale, de l’accord-cadre et de la clause fédérale et les expériences plus concluantes de la collaboration fédérale-provinciale dans la mise en oeuvre de certains traités internationaux, notamment le Protocole de Montréal relatif à des substances qui appauvrissent la couche d’ozone (1987). La deuxième partie du texte est consacrée à une analyse de la répartition des compétences constitutionnelles en matière environnementale au Canada. Aux termes d’une étude des compétences du Parlement en matière de droit criminel et en vertu de la théorie des dimensions nationales, le présent texte établit que les mesures législatives ayant pour finalité de contribuer à la lutte mondiale contre le réchauffement climatique devraient relever de la compétence prépondérante et concurrente du gouvernement fédéral.
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Hu, Y., Y. Xia, and Q. Fu. "Tropospheric temperature response to stratospheric ozone recovery in the 21st century." Atmospheric Chemistry and Physics 11, no. 15 (2011): 7687–99. http://dx.doi.org/10.5194/acp-11-7687-2011.
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Abstract. Recent simulations predicted that the stratospheric ozone layer will likely return to pre-1980 levels in the middle of the 21st century, as a result of the decline of ozone depleting substances under the Montreal Protocol. Since the ozone layer is an important component in determining stratospheric and tropospheric-surface energy balance, the recovery of stratospheric ozone may have significant impact on tropospheric-surface climate. Here, using multi-model results from both the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC-AR4) models and coupled chemistry-climate models, we show that as ozone recovery is considered, the troposphere is warmed more than that without considering ozone recovery, suggesting an enhancement of tropospheric warming due to ozone recovery. It is found that the enhanced tropospheric warming is mostly significant in the upper troposphere, with a global and annual mean magnitude of ~0.41 K for 2001–2050. We also find that relatively large enhanced warming occurs in the extratropics and polar regions in summer and autumn in both hemispheres, while the enhanced warming is stronger in the Northern Hemisphere than in the Southern Hemisphere. Enhanced warming is also found at the surface. The global and annual mean enhancement of surface warming is about 0.16 K for 2001–2050, with maximum enhancement in the winter Arctic.
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Laube, Johannes C., Norfazrin Mohd Hanif, Patricia Martinerie, et al. "Tropospheric observations of CFC-114 and CFC-114a with a focus on long-term trends and emissions." Atmospheric Chemistry and Physics 16, no. 23 (2016): 15347–58. http://dx.doi.org/10.5194/acp-16-15347-2016.
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Abstract. Chlorofluorocarbons (CFCs) are ozone-depleting substances as well as strong greenhouse gases, and the control of their production and use under the Montreal Protocol has had demonstrable benefits to both mitigation of increasing surface UV radiation and climate forcing. A global ban on consumption came into force in 2010, but there is evidence of continuing emissions of certain CFCs from a range of sources. One compound has received little attention in the literature, namely CFC-114 (C2Cl2F4). Of particular interest here is the differentiation between CFC-114 (CClF2CClF2) and its asymmetric isomeric form CFC-114a (CF3CCl2F) as atmospheric long-term measurements in the peer-reviewed literature to date have been assumed to represent the sum of both isomers with a time-invariant isomeric speciation. Here we report the first long-term measurements of the two isomeric forms separately, and find that they have different origins and trends in the atmosphere. Air samples collected at Cape Grim (41° S), Australia, during atmospheric background conditions since 1978, combined with samples collected from deep polar snow (firn) enable us to obtain a near-complete record of both gases since their initial production and release in the 1940s. Both isomers were present in the unpolluted atmosphere in comparably small amounts before 1960. The mixing ratio of CFC-114 doubled from 7.9 to 14.8 parts per trillion (ppt) between the start of the Cape Grim record in 1978 and the end of our record in 2014, while over the same time CFC-114a trebled from 0.35 to 1.03 ppt. Mixing ratios of both isomers are slowly decreasing by the end of this period. This is consistent with measurements of recent aircraft-based samples showing no significant interhemispheric mixing ratio gradient. We also find that the fraction of CFC-114a mixing ratio relative to that of CFC-114 increased from 4.2 to 6.9 % over the 37-year period. This contradicts the current tacit assumption used in international climate change and ozone depletion assessments that both isomers have been largely co-emitted and that their atmospheric concentration ratio has remained approximately constant in time. Complementary observations of air collected in Taiwan indicate a persisting source of CFC-114a in South East Asia which may have been contributing to the changing balance between the two isomers. In addition we present top-down global annual emission estimates of CFC-114 and CFC-114a derived from these measurements using a two-dimensional atmospheric chemistry-transport model. In general, the emissions for both compounds grew steadily during the 1980s, followed by a substantial reduction from the late 1980s onwards, which is consistent with the reduction of emission in response to the Montreal Protocol, and broadly consistent with bottom-up estimates derived by industry. However, we find that small but significant emissions of both isomers remain in 2014. Moreover the inferred changes to the ratio of emissions of the two isomers since the 1990s also indicate that the sources of the two gases are, in part, independent.
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Barrer, Laurence. "Le concept de démantèlement sensoriel dans l’autisme et la démarche scientifique." Perspectives Psy 59, no. 2 (2020): 175–83. http://dx.doi.org/10.1051/ppsy/202059175.
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L’objectif de l’article est de mettre en évidence la possible utilisation de la démarche scientifique (Bernard, 1865) pour quantifier un mécanisme psychique décrit par la psychanalyse. Le mécanisme de défense du moi dans l’autisme appelé démantèlement sensoriel y est pris comme exemple de recherche. À partir des travaux de D. Meltzer (1972, 1975, 1986) l’auteur a appliqué un protocole de méthodes mixtes, qualitative (phénoménologique) et quantitative (statistiques) pour le mettre en évidence chez l’enfant autiste en psychothérapie d’inspiration psychanalytique. La méthode qualitative est étayée sur une méthodologie où la description de critères de preuve sous-tend l’observation à partir de 43 vidéos de séance sur 127. Les résultats de cette recherche montrent que le processus de démantèlement est un mécanisme de défense du Moi observable et quantifiable signant l’évolution de l’intersubjectivité de l’enfant autiste avec le thérapeute.
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Fitzgerald, Gerald F. "Aviation Terrorism and the International Civil Aviation Organization." Canadian Yearbook of international Law/Annuaire canadien de droit international 25 (1988): 219–41. http://dx.doi.org/10.1017/s0069005800003180.
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SommaireL'acceptation quasi-universelle des Conventions de Tokyo, de La Haye et de Montréal constitue un élément important de la lutte contre le terrorisme aérien. L'OACI met l'accent sur la mise en oeuvre plus étendue de ces Conventions, soit par la soumission des États aux obligations prévues par leurs dispositions, soit par l'adoption et l'application de législations nationales appropriées. Le développement d'un protocole portant sur la répression des actes illicites dans les aéroports desservant l'aviation civile internationale comblera un vide grave dans la Convention de Montréal, laquelle ne vise pas les actes de terrorisme commis dans les aires d'attente.L'OACI s'occupe activement du développement des politiques en matières de protection de l'aviation civile internationale contre les attaques terroristes. Lors de son Assemblée de ig86, elle a adopté par consensus unanime une résolution consolidée à cet égard.L'amendement récent de l'Annexe ij de la Convention de Chicago a élevé un bon nombre de Pratiques Recommandées au niveau de Normes et a introduit de nouvelles dispositions sur la sécurité.En juin 1986, le Conseil de l'OACI a adopté une clause-type sur la sécurité de l'aviation qui pourrait être incorporée dans les accords bilatéraux de transport aérien régissant l'échange mutuel de droits de trafic. Une telle clause aidera à l'application des conventions portant sur la sécurité aérienne aussi bien qu'à l'application des Normes et Pratiques Recommandées de l'OACI relatives à ce sujet.L'enjeu de la lutte contre le terrorisme aérien exige rien de moins qu'une vigilance suivie de la part des forces de l'ordre. L'OACI joue un rôle très important dans cette lutte.
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Fernandez, Rafael P., Douglas E. Kinnison, Jean-Francois Lamarque, Simone Tilmes, and Alfonso Saiz-Lopez. "Impact of biogenic very short-lived bromine on the Antarctic ozone hole during the 21st century." Atmospheric Chemistry and Physics 17, no. 3 (2017): 1673–88. http://dx.doi.org/10.5194/acp-17-1673-2017.
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Abstract. Active bromine released from the photochemical decomposition of biogenic very short-lived bromocarbons (VSLBr) enhances stratospheric ozone depletion. Based on a dual set of 1960–2100 coupled chemistry–climate simulations (i.e. with and without VSLBr), we show that the maximum Antarctic ozone hole depletion increases by up to 14 % when natural VSLBr are considered, which is in better agreement with ozone observations. The impact of the additional 5 pptv VSLBr on Antarctic ozone is most evident in the periphery of the ozone hole, producing an expansion of the ozone hole area of ∼ 5 million km2, which is equivalent in magnitude to the recently estimated Antarctic ozone healing due to the implementation of the Montreal Protocol. We find that the inclusion of VSLBr in CAM-Chem (Community Atmosphere Model with Chemistry, version 4.0) does not introduce a significant delay of the modelled ozone return date to 1980 October levels, but instead affects the depth and duration of the simulated ozone hole. Our analysis further shows that total bromine-catalysed ozone destruction in the lower stratosphere surpasses that of chlorine by the year 2070 and indicates that natural VSLBr chemistry would dominate Antarctic ozone seasonality before the end of the 21st century. This work suggests a large influence of biogenic bromine on the future Antarctic ozone layer.
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Rigby, M., R. G. Prinn, S. O'Doherty, et al. "Re-evaluation of the lifetimes of the major CFCs and CH<sub>3</sub>CCl<sub>3</sub> using atmospheric trends." Atmospheric Chemistry and Physics Discussions 12, no. 9 (2012): 24469–99. http://dx.doi.org/10.5194/acpd-12-24469-2012.
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Abstract. Since the Montreal Protocol on substances that deplete the ozone layer and its amendments came into effect, growth rates of the major ozone depleting substances (ODS), particularly CFC-11, -12 and -113 and CH3CCl3, have declined markedly, paving the way for global stratospheric ozone recovery. Emissions have now fallen to relatively low levels, therefore the rate at which this recovery occurs will depend largely on the atmospheric lifetime of these compounds. The first ODS measurements began in the early 1970s along with the first lifetime estimates calculated by considering their atmospheric trends. We now have global mole fraction records spanning multiple decades, prompting this lifetime re-evaluation. Using surface measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) and the National Oceanic and Atmospheric Administration Global Monitoring Division (NOAA GMD) from 1978 to 2011, we estimated the lifetime of CFC-11, CFC-12, CFC-113 and CH3CCl3 using a multi-species inverse method. The CFC-11 lifetime of 45 yr, currently recommended in the World Meteorological Organisation (WMO) Scientific Assessment of Ozone Depletion, lies at the lower uncertainty bound of our estimates which are 524066 yr (1-sigma uncertainty) when AGAGE data were used, and 504066 yr when the NOAA network data were used. Our derived lifetime for CFC-113 is higher than the WMO estimates of 85 yr (10488123 using AGAGE, 10387122 using NOAA). Our estimates of the lifetime of CFC-12 and CH3CCl3 agree well with other recent estimates being 10885137 and 10484135 yr (CFC-12, AGAGE and NOAA, respectively) and 5.24.85.6 and 5.24.85.7 yr (CH3CCl3, AGAGE and NOAA, respectively).
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Rigby, M., R. G. Prinn, S. O'Doherty, et al. "Re-evaluation of the lifetimes of the major CFCs and CH<sub>3</sub>CCl<sub>3</sub> using atmospheric trends." Atmospheric Chemistry and Physics 13, no. 5 (2013): 2691–702. http://dx.doi.org/10.5194/acp-13-2691-2013.
Full textAbstract:
Abstract. Since the Montreal Protocol on Substances that Deplete the Ozone Layer and its amendments came into effect, growth rates of the major ozone depleting substances (ODS), particularly CFC-11, -12 and -113 and CH3CCl3, have declined markedly, paving the way for global stratospheric ozone recovery. Emissions have now fallen to relatively low levels, therefore the rate at which this recovery occurs will depend largely on the atmospheric lifetime of these compounds. The first ODS measurements began in the early 1970s along with the first lifetime estimates calculated by considering their atmospheric trends. We now have global mole fraction records spanning multiple decades, prompting this lifetime re-evaluation. Using surface measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) and the National Oceanic and Atmospheric Administration Global Monitoring Division (NOAA GMD) from 1978 to 2011, we estimated the lifetime of CFC-11, CFC-12, CFC-113 and CH3CCl3 using a multi-species inverse method. A steady-state lifetime of 45 yr for CFC-11, currently recommended in the most recent World Meteorological Organisation (WMO) Scientific Assessments of Ozone Depletion, lies towards the lower uncertainty bound of our estimates, which are 544861 yr (1-sigma uncertainty) when AGAGE data were used and 524561 yr when the NOAA network data were used. Our derived lifetime for CFC-113 is significantly higher than the WMO estimates of 85 yr, being 10999121 (AGAGE) and 10997124 (NOAA). New estimates of the steady-state lifetimes of CFC-12 and CH3CCl3 are consistent with the current WMO recommendations, being 11195132 and 11295136 yr (CFC-12, AGAGE and NOAA respectively) and 5.044.925.20 and 5.044.875.23 yr (CH3CCl3, AGAGE and NOAA respectively).
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Engel, Andreas, Harald Bönisch, Jennifer Ostermöller, Martyn P. Chipperfield, Sandip Dhomse, and Patrick Jöckel. "A refined method for calculating equivalent effective stratospheric chlorine." Atmospheric Chemistry and Physics 18, no. 2 (2018): 601–19. http://dx.doi.org/10.5194/acp-18-601-2018.
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Abstract. Chlorine and bromine atoms lead to catalytic depletion of ozone in the stratosphere. Therefore the use and production of ozone-depleting substances (ODSs) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent effective stratospheric chlorine (EESC) has been adopted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a refined formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the release time distribution. We show that a much better agreement with inorganic halogen loading from the chemistry transport model TOMCAT is achieved compared with using the current formulation. The refined formulation shows EESC levels in the year 1980 for the mid-latitude lower stratosphere, which are significantly lower than previously calculated. The year 1980 is commonly used as a benchmark to which EESC must return in order to reach significant progress towards halogen and ozone recovery. Assuming that – under otherwise unchanged conditions – the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than estimated in this region of the stratosphere with the current method for calculation of EESC. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We further discuss the value of EESC as a proxy for future evolution of inorganic halogen loading under changing atmospheric dynamics using simulations from the EMAC model. We show that while the expected changes in stratospheric transport lead to significant differences between EESC and modelled inorganic halogen loading at constant mean age, EESC is a reasonable proxy for modelled inorganic halogen on a constant pressure level.
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Zhang, H., S. Wu, Y. Huang, and Y. Wang. "Effects of stratospheric ozone recovery on photochemistry and ozone air quality in the troposphere." Atmospheric Chemistry and Physics 14, no. 8 (2014): 4079–86. http://dx.doi.org/10.5194/acp-14-4079-2014.
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Abstract. There has been significant stratospheric ozone depletion since the late 1970s due to ozone-depleting substances (ODSs). With the implementation of the Montreal Protocol and its amendments and adjustments, stratospheric ozone is expected to recover towards its pre-1980 level in the coming decades. In this study, we examine the implications of stratospheric ozone recovery for the tropospheric chemistry and ozone air quality with a global chemical transport model (GEOS-Chem). With a full recovery of the stratospheric ozone, the projected increases in ozone column range from 1% over the low latitudes to more than 10% over the polar regions. The sensitivity factor of troposphere ozone photolysis rate, defined as the percentage changes in surface ozone photolysis rate for 1% increase in stratospheric ozone column, shows significant seasonal variation but is always negative with absolute value larger than one. The expected stratospheric ozone recovery is found to affect the tropospheric ozone destruction rates much more than the ozone production rates. Significant decreases in surface ozone photolysis rates due to stratospheric ozone recovery are simulated. The global average tropospheric OH decreases by 1.7%, and the global average lifetime of tropospheric ozone increases by 1.5%. The perturbations to tropospheric ozone and surface ozone show large seasonal and spatial variations. General increases in surface ozone are calculated for each season, with increases by up to 0.8 ppbv in the remote areas. Increases in ozone lifetime by up to 13% are found in the troposphere. The increased lifetimes of tropospheric ozone in response to stratospheric ozone recovery enhance the intercontinental transport of ozone and global pollution, in particular for the summertime. The global background ozone attributable to Asian emissions is calculated to increase by up to 15% or 0.3 ppbv in the Northern Hemisphere in response to the projected stratospheric ozone recovery.
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Vaníček, K., L. Metelka, P. Skřivánková, and M. Staněk. "Dobson, Brewer, ERA-40 and ERA-Interim original and merged total ozone data sets – evaluation of differences: a case study, Hradec Králové (Czech), 1961–2010." Earth System Science Data 4, no. 1 (2012): 91–100. http://dx.doi.org/10.5194/essd-4-91-2012.
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Abstract. Homogenized data series of total ozone measurements taken by the regularly and well calibrated Dobson and Brewer spectrophotometers at Hradec Králové (Czech) and the data from the re-analyses ERA-40 and ERA-Interim were merged and compared to investigate differences between the particular data sets originated in Central Europe, the Northern Hemisphere (NH) mid-latitudes. The Dobson-to-Brewer transfer function and the algorithm for approximation of the data from the re-analyses were developed, tested and applied for creation of instrumentally consistent and completed total ozone data series of the 50-yr period 1961–2010 of observations. This correction has reduced the well-known seasonal differences between Dobson and Brewer data below the 1% calibration limit of the spectrophotometers. Incorporation of the ERA-40 and ERA-Interim total ozone data on days with missing measurements significantly improved completeness and reliability of the data series mainly in the first two decades of the period concerned. Consistent behaviour of the original and corrected/merged data sets was found in the pre-ozone-hole period (1961–1985). In the post-Pinatubo (1994–2010) era the data series show seasonal differences that can introduce uncertainty in estimation of ozone recovery mainly in the winter-spring season when the effect of the Montreal Protocol and its Amendments is expected. All the data sets confirm substantial depletion of ozone also in the summer months that gives rise to the question about its origin. The merged and completed data series of total ozone will be further analyzed to quantify chemical ozone losses and contribution of natural atmospheric processes to the ozone depletion over the region. This case study points out the importance of selection and evaluation of the quality and consistency of the input data sets used in estimation of long-term ozone changes including recovery of the ozone layer over the selected areas. Data are available from the PANGAEA database at doi:10.1594/PANGAEA.779819.
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Vaníček, K., L. Metelka, P. Skřivánková, and M. Staněk. "Dobson, Brewer, ERA-40 and ERA-Interim original and assimilated total ozone data sets – evaluation of differences: a case study, Hradec Králové (Czech), 1961–2010." Earth System Science Data Discussions 5, no. 1 (2012): 445–73. http://dx.doi.org/10.5194/essdd-5-445-2012.
Full textAbstract:
Abstract. Homogenized data series of total ozone measurements taken by the regularly and well calibrated Dobson and Brewer spectrophotometers at Hradec Králové (Czech) and the data from the re-analyses ERA-40 and ERA-Interim were assimilated and combined to investigate differences between the particular data sets over Central Europe, the NH mid-latitudes. The Dobson-to-Brewer transfer function and the algorithm for approximation of the data from the re-analyses were developed, tested and applied for creation of instrumentally consistent and completed total ozone data series of the 50-yr period 1961–2010 of observations. The assimilation has reduced the well-known seasonal differences between Dobson and Brewer data below the 1% calibration limit of the spectrophotometers. Incorporation of the ERA-40 and ERA-Interim total ozone data on days with missing measurements significantly improved completeness and reliability of the data series mainly in the first two decades of the period concerned. Consistent behaviour of the original and assimilated data sets was found in the pre-ozone-hole period (1961–1985). In the post-Pinatubo (1994–2010) era the data series show seasonal differences that can introduce uncertainty in estimation of ozone recovery mainly in the winter-spring season when the effect of the Montreal Protocol and its Amendments is expected. All the data sets confirm substantial depletion of ozone also in the summer months that gives rise to the question about its origin. The assimilated and completed data series of total ozone will be further analyzed to quantify chemical ozone losses and contribution of natural atmospheric processes to the ozone depletion over the region. This case study points out importance of selection and evaluation of the quality and consistency of the input data sets used in estimation of long-term ozone changes including recovery of the ozone layer over the selected areas. Data are available from the PANGAEA database at http://dx.doi.org/10.1594/PANGAEA.779819.
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Keeble, James, Ewa M. Bednarz, Antara Banerjee, et al. "Diagnosing the radiative and chemical contributions to future changes in tropical column ozone with the UM-UKCA chemistry–climate model." Atmospheric Chemistry and Physics 17, no. 22 (2017): 13801–18. http://dx.doi.org/10.5194/acp-17-13801-2017.
Full textAbstract:
Abstract. Chemical and dynamical drivers of trends in tropical total-column ozone (TCO3) for the recent past and future periods are explored using the UM-UKCA (Unified Model HadGEM3-A (Hewitt et al., 2011) coupled with the United Kingdom Chemistry and Aerosol scheme) chemistry–climate model. A transient 1960–2100 simulation is analysed which follows the representative concentration pathway 6.0 (RCP6.0) emissions scenario for the future. Tropical averaged (10° S–10° N) TCO3 values decrease from the 1970s, reach a minimum around 2000 and return to their 1980 values around 2040, consistent with the use and emission of halogenated ozone-depleting substances (ODSs), and their later controls under the Montreal Protocol. However, when the ozone column is subdivided into three partial columns (PCO3) that cover the upper stratosphere (PCO3US), lower stratosphere (PCO3LS) and troposphere (PCO3T), significant differences in the temporal behaviour of the partial columns are seen. Modelled PCO3T values under the RCP6.0 emissions scenario increase from 1960 to 2000 before remaining approximately constant throughout the 21st century. PCO3LS values decrease rapidly from 1960 to 2000 and remain constant from 2000 to 2050, before gradually decreasing further from 2050 to 2100 and never returning to their 1980s values. In contrast, PCO3US values decrease from 1960 to 2000, before increasing rapidly throughout the 21st century and returning to 1980s values by ∼ 2020, and reach significantly higher values by 2100. Using a series of idealised UM-UKCA time-slice simulations with concentrations of well-mixed greenhouse gases (GHGs) and halogenated ODS species set to either year 2000 or 2100 levels, we examine the main processes that drive the PCO3 responses in the three regions and assess how these processes change under different emission scenarios. Finally, we present a simple, linearised model to describe the future evolution of tropical stratospheric column ozone values based on terms representing time-dependent abundances of GHG and halogenated ODS.
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St-Pierre, Annie, Anne-Marie Charron, Pamela Doyon-Plourde, and Caroline Quach. "Determinants of Protection Against Measles Infection in a Vaccinated Healthcare Worker." Infection Control & Hospital Epidemiology 41, S1 (2020): s185. http://dx.doi.org/10.1017/ice.2020.722.
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Background: In 2019, a measles community outbreak resulted in a secondary case in a health care worker (HCW) working in a pediatric hospital in Montral, Canada. Following the event, HCWs were screened to identify individuals susceptible to measles infection based on serology results. Objective: Our aim was to assess measles seroprotection rates and to evaluate vaccine responses of susceptible HCWs using commercial enzyme immunoassay (EIA) or enzyme linked immunosorbent assay (ELISA). Methods: Emergency department (ED) employees, including doctors, were screened for measles susceptibility as part of a postoutbreak measure by the hospital occupational health service. Demographic information was collected. Measles history and vaccination information were collected using a personal vaccination booklet, employee vaccination profile, or the Qubec vaccination registry. According to the Quebec Immunization Protocol (PIQ), individuals born before 1970, or who have received 2 doses of a measles-containing vaccines are considered protected. Individuals with undetectable or equivocal antibody levels were considered at risk of measles infection. These individuals were offered vaccination and were tested for vaccine response 4 weeks after vaccination. Results: Anti-IgG measles antibody results, demographic information, and vaccination information were obtained for 257 employees. The results are currently available for 233 HCWs: 224 HCWs (96%) were seropositive, 7 (3%) were seronegative, and 2 were equivocal. Among seronegative individuals, 6 (85.7%) were born after 1980 and 3 (42.9%) had received 2 doses of a measles-containing vaccine. Of those with an equivocal result, 1 (50%) had received 2 doses and 1 (50%), born after 1970, did not confirm vaccination status. Finally, 9 (4%) of seropositive individuals were not vaccinated; of whom 8 (88.9%) were born before 1970. Conclusions: Our preliminary results suggest that the 95% immunity threshold that is usually required to prevent secondary transmission of measles has been reached in our ED HCW cohort. Even years after the second MMR dose, HCWs remain well protected. Relying on documented vaccination status is thus acceptable.Funding: NoneDisclosures: None
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Arosio, Carlo, Alexei Rozanov, Elizaveta Malinina, Mark Weber, and John P. Burrows. "Merging of ozone profiles from SCIAMACHY, OMPS and SAGE II observations to study stratospheric ozone changes." Atmospheric Measurement Techniques 12, no. 4 (2019): 2423–44. http://dx.doi.org/10.5194/amt-12-2423-2019.
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Abstract. This paper presents vertically and zonally resolved merged ozone time series from limb measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) and the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP). In addition, we present the merging of the latter two data sets with zonally averaged profiles from Stratospheric Aerosol and Gas Experiment (SAGE) II. The retrieval of ozone profiles from SCIAMACHY and OMPS-LP is performed using an inversion algorithm developed at the University of Bremen. To optimize the merging of these two time series, we use data from the Microwave Limb Sounder (MLS) as a transfer function and we follow two approaches: (1) a conventional method involving the calculation of deseasonalized anomalies and (2) a “plain-debiasing” approach, generally not considered in previous similar studies, which preserves the seasonal cycles of each instrument. We find a good correlation and no significant drifts between the merged and MLS time series. Using the merged data set from both approaches, we apply a multivariate regression analysis to study ozone changes in the 20–50 km range over the 2003–2018 period. Exploiting the dense horizontal sampling of the instruments, we investigate not only the zonally averaged field, but also the longitudinally resolved long-term ozone variations, finding an unexpected and large variability, especially at mid and high latitudes, with variations of up to 3 %–5 % per decade at altitudes around 40 km. Significant positive linear trends of about 2 %–4 % per decade were identified in the upper stratosphere between altitudes of 38 and 45 km at mid latitudes. This is in agreement with the predicted recovery of upper stratospheric ozone, which is attributed to both the adoption of measures to limit the release of halogen-containing ozone-depleting substances (Montreal Protocol) and the decrease in stratospheric temperature resulting from the increasing concentration of greenhouse gases. In the tropical stratosphere below 25 km negative but non-significant trends were found. We compare our results with previous studies and with short-term trends calculated over the SCIAMACHY period (2002–2012). While generally a good agreement is found, some discrepancies are seen in the tropical mid stratosphere. Regarding the merging of SAGE II with SCIAMACHY and OMPS-LP, zonal mean anomalies are taken into consideration and ozone trends before and after 1997 are calculated. Negative trends above 30 km are found for the 1985–1997 period, with a peak of −6 % per decade at mid latitudes, in agreement with previous studies. The increase in ozone concentration in the upper stratosphere is confirmed over the 1998–2018 period. Trends in the tropical stratosphere at 30–35 km show an interesting behavior: over the 1998–2018 period a negligible trend is found. However, between 2004 and 2011 a negative long-term change is detected followed by a positive change between 2012 and 2018. We attribute this behavior to dynamical changes in the tropical middle stratosphere.
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von Hobe, M., S. Bekki, S. Borrmann, et al. "Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions." Atmospheric Chemistry and Physics Discussions 12, no. 11 (2012): 30661–754. http://dx.doi.org/10.5194/acpd-12-30661-2012.
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Abstract. Significant reductions in stratospheric ozone occur inside the polar vortices each spring when chlorine radicals produced by heterogeneous reactions on cold particle surfaces in winter destroy ozone mainly in two catalytic cycles, the ClO dimer cycle and the ClO/BrO cycle. Chlorofluorocarbons (CFCs), which are responsible for most of the chlorine currently present in the stratosphere, have been banned by the Montreal Protocol and its amendments, and the ozone layer is predicted to recover to 1980 levels within the next few decades. During the same period, however, climate change is expected to alter the temperature, circulation patterns and chemical composition in the stratosphere, and possible geo-engineering ventures to mitigate climate change may lead to additional changes. To realistically predict the response of the ozone layer to such influences requires the correct representation of all relevant processes. The European project RECONCILE has comprehensively addressed remaining questions in the context of polar ozone depletion, with the objective to quantify the rates of some of the most relevant, yet still uncertain physical and chemical processes. To this end RECONCILE used a broad approach of laboratory experiments, two field missions in the Arctic winter 2009/10 employing the high altitude research aircraft M55-Geophysica and an extensive match ozone sonde campaign, as well as microphysical and chemical transport modelling and data assimilation. Some of the main outcomes of RECONCILE are as follows: (1) vortex meteorology: the 2009/10 Arctic winter was unusually cold at stratospheric levels during the six-week period from mid-December 2009 until the end of January 2010, with reduced transport and mixing across the polar vortex edge; polar vortex stability and how it is influenced by dynamic processes in the troposphere has led to unprecedented, synoptic-scale stratospheric regions with temperatures below the frost point; in these regions stratospheric ice clouds have been observed, extending over >106km2 during more than 3 weeks. (2) Particle microphysics: heterogeneous nucleation of nitric acid trihydrate (NAT) particles in the absence of ice has been unambiguously demonstrated; conversely, the synoptic scale ice clouds also appear to nucleate heterogeneously; a variety of possible heterogeneous nuclei has been characterised by chemical analysis of the non-volatile fraction of the background aerosol; substantial formation of solid particles and denitrification via their sedimentation has been observed and model parameterizations have been improved. (3) Chemistry: strong evidence has been found for significant chlorine activation not only on polar stratospheric clouds (PSCs) but also on cold binary aerosol; laboratory experiments and field data on the ClOOCl photolysis rate and other kinetic parameters have been shown to be consistent with an adequate degree of certainty; no evidence has been found that would support the existence of yet unknown chemical mechanisms making a significant contribution to polar ozone loss. (4) Global modelling: results from process studies have been implemented in a prognostic chemistry climate model (CCM); simulations with improved parameterisations of processes relevant for polar ozone depletion are evaluated against satellite data and other long term records using data assimilation and detrended fluctuation analysis. Finally, measurements and process studies within RECONCILE were also applied to the winter 2010/11, when special meteorological conditions led to the highest chemical ozone loss ever observed in the Arctic. In addition to quantifying the 2010/11 ozone loss and to understand its causes including possible connections to climate change, its impacts were addressed, such as changes in surface ultraviolet (UV) radiation in the densely populated northern mid-latitudes.