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Solar proton events (SPEs) affect the Earth's atmosphere, causing additional ionization in the high-latitude mesosphere and stratosphere. Ionization rates from such solar proton events maximize in the stratosphere, but the formation of ozone-depleting nitrogen and hydrogen oxides begins at mesospheric altitudes. The destruction of mesospheric ozone is associated with protons with energies of about 10 MeV and higher and will strongly depend on the intensity of the flux of these particles. Most studies investigating the impact of SPEs on the characteristics of the middle atmosphere have been based on either simulations or reanalysis datasets, and some studies have used satellite observations to validate model results. We study the impact of SPEs on cold-season ozone loss in both the northern and southern hemispheres using Aura MLS mesospheric ozone measurements over the 2004 to 2024 period. Here, we show how strongly SPEs can deplete polar mesospheric ozone in different hemispheres and attempt to evaluate this dependence on the intensity of solar proton events. We found that moderate SPEs consisting of protons with an energy of more than 10 MeV and a flux intensity of more than 100 pfu destroy mesospheric ozone in the northern hemisphere up to 47% and in the southern hemisphere up to 33%. For both hemispheres, the peak of winter ozone loss was observed at about 76 km. In the northern hemisphere, maximum winter ozone loss was observed on the second day after a solar proton event, but in the southern hemisphere, winter ozone depletion was already detected on the first day. In the southern hemisphere, mesospheric ozone concentrations return to pre-event levels on the ninth day after a solar proton event, but in the northern hemisphere, even on the tenth day after a solar proton event, the mesospheric ozone layer may not be fully recovered. The strong SPEs with a proton flux intensity of more than 1000 pfu lead to a maximum winter ozone loss of up to 85% in the northern hemisphere, and in the southern hemisphere winter, ozone loss reaches 73%. [ABSTRACT FROM AUTHOR]

Large constellations of small satellites will significantly increase the number of objects orbiting the Earth. Satellites burn up at the end of service life during reentry, generating aluminum oxides as the main byproduct. These are known catalysts for chlorine activation that depletes ozone in the stratosphere. We present the first atomic‐scale molecular dynamics simulation study to resolve the oxidation process of the satellite's aluminum structure during mesospheric reentry, and investigate the ozone depletion potential from aluminum oxides. We find that the demise of a typical 250‐kg satellite can generate around 30 kg of aluminum oxide nanoparticles, which may endure for decades in the atmosphere. Aluminum oxide compounds generated by the entire population of satellites reentering the atmosphere in 2022 are estimated at around 17 metric tons. Reentry scenarios involving mega‐constellations point to over 360 metric tons of aluminum oxide compounds per year, which can lead to significant ozone depletion. Plain Language Summary: With ongoing plans for many constellations of small satellites, the number of objects orbiting the Earth is expected to continue increasing in the foreseeable future. At the end of service life, satellites are disposed into the atmosphere, burning up during the process and generating aluminum oxides, which are known to accelerate ozone depletion. The environmental impacts from the reentry of satellites are currently poorly understood. This paper investigates the oxidation process of the satellite's aluminum content during atmospheric reentry utilizing atomic‐scale molecular dynamics simulations. We find that the population of reentering satellites in 2022 caused a 29.5% increase of aluminum in the atmosphere above the natural level, resulting in around 17 metric tons of aluminum oxides injected into the mesosphere. The byproducts generated by the reentry of satellites in a future scenario where mega‐constellations come to fruition can reach over 360 metric tons per year. As aluminum oxide nanoparticles may remain in the atmosphere for decades, they can cause significant ozone depletion. Key Points: We present the first atomic‐scale molecular dynamics simulation of high‐temperature aluminum ablation during reentry from low‐Earth orbitThe amount of aluminum oxide nanoparticles generated is quantified and the accumulation in the atmosphere is estimatedThe long‐term accumulation of aluminum oxides from reentering satellites can cause significant ozone depletion [ABSTRACT FROM AUTHOR]

Composting is a waste management practice that converts organic waste into a product that can be used safely and beneficially as a bio-fertiliser and soil amendment. Non-methane volatile organic compounds (NMVOCs) from composting are known to cause damage to human health and the environment. The impact of waste management on the environment and workers is recognised as a growing environmental and public health concern. Measurements of NMVOCs emitted during composting have been carried out only in a few studies. NMVOC emissions are typically reported as a group rather than as species or speciation profiles. Recognising the need to investigate the issues associated with NMVOCs, the objective of this study is to estimate variation in life cycle assessment (LCA) results when NMVOCs are considered individual emissions compared to grouped emissions and to compare midpoint and endpoint life cycle impact assessment (LCIA) methods. In general, the ReCiPe 2016 LCIA method estimated the highest impact from the composting process in comparison to IMPACT World+ and EF 3.0 for the impact categories of ozone formation, stratospheric ozone depletion, and particulate matter formation. For ReCiPe 2016 and IMPACT World+, the NMVOC emissions were not linked to human toxicity characterisation factors, meaning that the contribution from NMVOC towards human health risks in and around composting facilities could be underestimated. Using individual NMVOCs helps to additionally estimate the impacts of composting on freshwater ecotoxicity and human carcinogenic and non-carcinogenic toxicity potential. If ecotoxicity or toxicity issues are indicated, then LCA should be accompanied by suitable risk assessment measures for the respective life cycle stage. [ABSTRACT FROM AUTHOR]

The January 2022 eruption of Hunga Tonga‐Hunga Ha'apai (HTHH) injected a huge amount (∼150 Tg) of water vapor (H2O) into the stratosphere, along with small amount of SO2. An off‐line 3‐D chemical transport model (CTM) successfully reproduces the spread of the injected H2O through October 2023 as observed by the Microwave Limb Sounder. Dehydration in the 2023 Antarctic polar vortex caused the first substantial (∼20 Tg) removal of HTHH H2O from the stratosphere. The CTM indicates that this process will dominate removal of HTHH H2O for the coming years, giving an overall e‐folding timescale of 4 years; around 25 Tg of the injected H2O is predicted to still remain in the stratosphere by 2030. Following relatively low Antarctic column ozone in midwinter 2023 due to transport effects, additional springtime depletion due to H2O‐related chemistry was small and maximized at the vortex edge (10 DU in column). Plain Language Summary: Around 150 Tg (150 million tons) of water vapor was injected into the stratosphere during the eruption of Hunga Tonga‐Hunga Ha'apai. Water vapor is a greenhouse gas and this increase is expected to have a warming effect in the troposphere, as well causing perturbations in stratospheric chemistry and aerosols. We use an atmospheric model to study the residence time of this excess water vapor and its impact on the recent Antarctic ozone hole. The model performance is evaluated by comparison with satellite measurements. Wintertime dehydration in the Antarctic stratosphere in 2023 is found to be an important mechanism for removal of the volcanic water from the stratosphere. However, the overall removal rate is predicted to be slow; around 25 Tg (17%) is still present in 2030. The direct impact of the excess water vapor on ozone via chemical processes in the Antarctic ozone hole in 2023 is small. Key Points: Antarctic dehydration is a major removal pathway of stratospheric H2O injected from Hunga Tonga‐Hunga Ha'apai (HTHH) eruptionHTHH H2O caused small (up to 10 DU) additional chemical ozone depletion in 2023 Antarctic springModel indicates e‐folding timescale of 4 years for removal of HTHH H2O from stratosphere [ABSTRACT FROM AUTHOR]

This research aims to comprehensively examine the clearness index (KT), total ozone column (TOC), and ultraviolet A (UVA) and ultraviolet B radiation (UVB) over Lumbini, Nepal (27°28' N, 83°16' E, and 150 m above sea level) throughout the 11 years of solar cycle 24 (2008 to 2018). The Lumbini, a highly polluted region, is important in advancing the identification and analysis of TOC variations across regions with similar geographical and climatic attributes. Data from the Ozone Monitoring Instrument (OMI) of the EOS-AURA satellite of NASA were used to analyze the daily, monthly, seasonal, and annual trends in the clearness index (KT), ultraviolet A (UVA), ultraviolet B (UVB), and TOC from the Comprehensive Environmental Data Archive (CEDA). The study found that the yearly averages for KT, TOC, UVA, and UVB were 0.55 ± 0.13, 272 ± 14 DU, 12.61 ± 3.50 W/m2, and 0.32 ± 0.11 W/m2, respectively. These values provide insights into the long-term variations in atmospheric parameters at Lumbini. The study also applied the continuous wavelet transform (CWT) to analyze KT, TOC, UVA, and UVB temporal variations. The power density peak of 35,000 DU2 in the TOC was observed from the end of 2010 to the end of 2011, within 8.5 years, underscoring the significance of analyzing TOC dynamics over extended durations to understand atmospheric behavior comprehensively. [ABSTRACT FROM AUTHOR]

Abstract Stratospheric ozone depletion from halocarbons is partly countered by pollution‐driven increases in tropospheric ozone, with transport connecting the two. While recognizing this connection, the ozone assessment's evaluation of observations and processes have often split the chapters at the tropopause boundary. Using a chemistry‐transport model we find that air‐pollution ozone enhancements in the troposphere spill over into the stratosphere at significant rates, that is, 13%–34% of the excess tropospheric burden appears in the lowermost extra‐tropical stratosphere. As we track the anticipated recovery of the observed ozone depletion, we should recognize that two tenths of that recovery may come from the transport of increasing tropospheric ozone into the stratosphere.

Abstract Large constellations of small satellites will significantly increase the number of objects orbiting the Earth. Satellites burn up at the end of service life during reentry, generating aluminum oxides as the main byproduct. These are known catalysts for chlorine activation that depletes ozone in the stratosphere. We present the first atomic‐scale molecular dynamics simulation study to resolve the oxidation process of the satellite's aluminum structure during mesospheric reentry, and investigate the ozone depletion potential from aluminum oxides. We find that the demise of a typical 250‐kg satellite can generate around 30 kg of aluminum oxide nanoparticles, which may endure for decades in the atmosphere. Aluminum oxide compounds generated by the entire population of satellites reentering the atmosphere in 2022 are estimated at around 17 metric tons. Reentry scenarios involving mega‐constellations point to over 360 metric tons of aluminum oxide compounds per year, which can lead to significant ozone depletion.

Abstract The January 2022 eruption of Hunga Tonga‐Hunga Ha'apai (HTHH) injected a huge amount (∼150 Tg) of water vapor (H2O) into the stratosphere, along with small amount of SO2. An off‐line 3‐D chemical transport model (CTM) successfully reproduces the spread of the injected H2O through October 2023 as observed by the Microwave Limb Sounder. Dehydration in the 2023 Antarctic polar vortex caused the first substantial (∼20 Tg) removal of HTHH H2O from the stratosphere. The CTM indicates that this process will dominate removal of HTHH H2O for the coming years, giving an overall e‐folding timescale of 4 years; around 25 Tg of the injected H2O is predicted to still remain in the stratosphere by 2030. Following relatively low Antarctic column ozone in midwinter 2023 due to transport effects, additional springtime depletion due to H2O‐related chemistry was small and maximized at the vortex edge (10 DU in column).

Solar proton events (SPEs) affect the Earth’s atmosphere, causing additional ionization in the high-latitude mesosphere and stratosphere. Ionization rates from such solar proton events maximize in the stratosphere, but the formation of ozone-depleting nitrogen and hydrogen oxides begins at mesospheric altitudes. The destruction of mesospheric ozone is associated with protons with energies of about 10 MeV and higher and will strongly depend on the intensity of the flux of these particles. Most studies investigating the impact of SPEs on the characteristics of the middle atmosphere have been based on either simulations or reanalysis datasets, and some studies have used satellite observations to validate model results. We study the impact of SPEs on cold-season ozone loss in both the northern and southern hemispheres using Aura MLS mesospheric ozone measurements over the 2004 to 2024 period. Here, we show how strongly SPEs can deplete polar mesospheric ozone in different hemispheres and attempt to evaluate this dependence on the intensity of solar proton events. We found that moderate SPEs consisting of protons with an energy of more than 10 MeV and a flux intensity of more than 100 pfu destroy mesospheric ozone in the northern hemisphere up to 47% and in the southern hemisphere up to 33%. For both hemispheres, the peak of winter ozone loss was observed at about 76 km. In the northern hemisphere, maximum winter ozone loss was observed on the second day after a solar proton event, but in the southern hemisphere, winter ozone depletion was already detected on the first day. In the southern hemisphere, mesospheric ozone concentrations return to pre-event levels on the ninth day after a solar proton event, but in the northern hemisphere, even on the tenth day after a solar proton event, the mesospheric ozone layer may not be fully recovered. The strong SPEs with a proton flux intensity of more than 1000 pfu lead to a maximum winter ozone loss of up to 85% in the northern hemisphere, and in the southern hemisphere winter, ozone loss reaches 73%.

Background: The world faces a significant global health threat – climate change, which makes creating more environmentally sustainable healthcare systems necessary. As a resource-intensive specialty, anesthesiology contributes to a substantial fraction of healthcare's environmental impact. This alarming situation invites us to reconsider the ecological health determinants and calls us to action. Methods: We conducted a single-center qualitative study involving an online survey to explore the environmental sustainability from anesthesia providers' perspectives in a center implementing internal environmentally-sustainable anesthesia guidelines. We asked care providers how they perceive the importance of environmental issues in their work; the adverse effects they see on ecological sustainability in anesthesia practice; what measures they take to make anesthesia more environmentally friendly; what barriers they face in trying to do so; and why they are unable to adopt ecologically friendly practices in some instances. Using a thematic analysis approach, we identified dominating themes in participants' responses. Results: A total of 62 anesthesia providers completed the online survey. 89% of the participants stated that environmental sustainability is essential in their work, and 95% reported that they implement measures to make their practice greener. A conscious choice of anesthetics was identified as the most common step the respondents take to reduce the environmental impact of anesthesia. Waste production and improper waste management was the most frequently mentioned anesthesia-associated threat to the environment. Lacking knowledge/teaching in sustainability themes was recognized as a crucial barrier to achieving ecology goals. Conclusions: Sustainable anesthesia initiatives have the potential to both encourage engagement among anesthesia providers and raise awareness of this global issue. These findings inspire opportunities for action in sustainable anesthesia and broaden the capacity to decrease the climate impact of health care. [ABSTRACT FROM AUTHOR]

Stratospheric climate change is an important part of global change.Observational and modeling studies disclosed that the stratosphere had shown in general a cooling trend during around the last 20 years of the 20th century.Ozone depletion is believed to have caused the preponderance of the cooling in the lower stratosphere （around 15~25 km altitude）； both ozone depletion and increases in greenhouse gases are believed to have driven the cooling in the middle and upper stratosphere （around 25~50 km altitude）.Stratospheric cooling was comparably consistent throughout the year at the tropical latitudes.However， the temperature trends in the polar stratosphere shown a characteristic of annual cycle， which is probably related to the severe polar ozone depletion during springs and the significant changes of the Brewer-Dobson circulation during winters.Anomalously， during around the Decembers from 1980 to 2000， a warming trend occurred both in the middle and upper layers of the Antarctic stratosphere and almost in the whole layer of the Arctic stratosphere.In this paper， we utilized the Middle and Upper Atmosphere Model （MUAM） to investigate the decadal changes between stratospheric climatic states during Decembers at the end of the 20th century.The impacts of changes in lower boundary condition （LBC）， carbon dioxide and ozone concentrations on stratospheric temperature trends are assessed， respectively， based on a set of sensitivity experiments， while the mechanism differences between the local warming in the Antarctic and Arctic stratosphere are preferentially discussed.The results obtained show that during the Decembers of 1990s （relative to those of 1980s）， the westerly in the Arctic mid-to-upper stratosphere decelerates and the temperature in the mid-to-lower layers increases.This is mainly attributable to the significant strengthening （weakening） of the upward propagation of stationary planetary wave with zonal wavenumber 1 （2） that resulted from the change in LBC.Meanwhile， in the Antarctic stratosphere， the westerly （easterly） in the lower （mid-to-upper） layers accelerates （decelerates） and the temperature decreases （increases）.This is mainly correlated with the significant ozone depletion occurred in the Antarctic lower stratosphere， though the change in LBC and the local increase of ozone in the middle layers also have some contribution.The acceleration of the polar vortex induced by the ozone depletion in the lower layers， which makes the propagation environment or condition more advantageous for waves 1 and 2 （wave 1 is dominant） to propagate increasingly and higher into the stratosphere， may be the main cause that ultimately leads to the warming in the mid-to-upper layers.

Global and regional atmospheric measurements and modeling can play key roles in discovering and quantifying unexpected nascent emissions of environmentally important substances. We focus here on three hydrochlorofluorocarbons (HCFCs) that are restricted by the Montreal Protocol because of their roles in stratospheric ozone depletion. Based on measurements of archived air samples and on in situ measurements at stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, we report global abundances, trends, and regional enhancements for HCFC-132b ([Formula: see text]), which is newly discovered in the atmosphere, and updated results for HCFC-133a ([Formula: see text]) and HCFC-31 ([Formula: see text]ClF). No purposeful end-use is known for any of these compounds. We find that HCFC-132b appeared in the atmosphere 20 y ago and that its global emissions increased to 1.1 Gg⋅y-1 by 2019. Regional top-down emission estimates for East Asia, based on high-frequency measurements for 2016-2019, account for ∼95% of the global HCFC-132b emissions and for ∼80% of the global HCFC-133a emissions of 2.3 Gg⋅y-1 during this period. Global emissions of HCFC-31 for the same period are 0.71 Gg⋅y-1 Small European emissions of HCFC-132b and HCFC-133a, found in southeastern France, ceased in early 2017 when a fluorocarbon production facility in that area closed. Although unreported emissive end-uses cannot be ruled out, all three compounds are most likely emitted as intermediate by-products in chemical production pathways. Identification of harmful emissions to the atmosphere at an early stage can guide the effective development of global and regional environmental policy.

Composting is a waste management practice that converts organic waste into a product that can be used safely and beneficially as a bio-fertiliser and soil amendment. Non-methane volatile organic compounds (NMVOCs) from composting are known to cause damage to human health and the environment. The impact of waste management on the environment and workers is recognised as a growing environmental and public health concern. Measurements of NMVOCs emitted during composting have been carried out only in a few studies. NMVOC emissions are typically reported as a group rather than as species or speciation profiles. Recognising the need to investigate the issues associated with NMVOCs, the objective of this study is to estimate variation in life cycle assessment (LCA) results when NMVOCs are considered individual emissions compared to grouped emissions and to compare midpoint and endpoint life cycle impact assessment (LCIA) methods. In general, the ReCiPe 2016 LCIA method estimated the highest impact from the composting process in comparison to IMPACT World+ and EF 3.0 for the impact categories of ozone formation, stratospheric ozone depletion, and particulate matter formation. For ReCiPe 2016 and IMPACT World+, the NMVOC emissions were not linked to human toxicity characterisation factors, meaning that the contribution from NMVOC towards human health risks in and around composting facilities could be underestimated. Using individual NMVOCs helps to additionally estimate the impacts of composting on freshwater ecotoxicity and human carcinogenic and non-carcinogenic toxicity potential. If ecotoxicity or toxicity issues are indicated, then LCA should be accompanied by suitable risk assessment measures for the respective life cycle stage.

This research aims to comprehensively examine the clearness index (KT), total ozone column (TOC), and ultraviolet A (UVA) and ultraviolet B radiation (UVB) over Lumbini, Nepal (27°28’ N, 83°16’ E, and 150 m above sea level) throughout the 11 years of solar cycle 24 (2008 to 2018). The Lumbini, a highly polluted region, is important in advancing the identification and analysis of TOC variations across regions with similar geographical and climatic attributes. Data from the Ozone Monitoring Instrument (OMI) of the EOS-AURA satellite of NASA were used to analyze the daily, monthly, seasonal, and annual trends in the clearness index (KT), ultraviolet A (UVA), ultraviolet B (UVB), and TOC from the Comprehensive Environmental Data Archive (CEDA). The study found that the yearly averages for KT, TOC, UVA, and UVB were 0.55 ± 0.13, 272 ± 14 DU, 12.61 ± 3.50 W/m2, and 0.32 ± 0.11 W/m2, respectively. These values provide insights into the long-term variations in atmospheric parameters at Lumbini. The study also applied the continuous wavelet transform (CWT) to analyze KT, TOC, UVA, and UVB temporal variations. The power density peak of 35,000 DU2 in the TOC was observed from the end of 2010 to the end of 2011, within 8.5 years, underscoring the significance of analyzing TOC dynamics over extended durations to understand atmospheric behavior comprehensively.

Energetic electron precipitation (EEP) into the atmosphere are considered to play an important role in the natural forcing of the ozone variability and dynamics of the middle atmosphere during magnetospheric and geomagnetic disturbances. Energetic electrons from the radiation belt spill out into the atmosphere during geomagnetic disturbances and cause additional ionization rates in the polar middle atmosphere. These rates of induced atmospheric ionization lead to the formation of radicals in ion-molecular reactions at the heights of the mesosphere with the formation of reactive compounds of odd nitrogen groups NO y and odd hydrogen groups HO x . These compounds are involved in catalytic reactions that destroy ozone. The percentage of ozone destruction can depend not only intensity of EEP but also on season where it happens. In this work, we study mesospheric ozone depletion depending on seasons and precipitating energetic electrons with energies from keV up to relativistic energies about 1 MeV, based on the NOAA POES satellites observations in 2003. For estimation ozone deplation we use a one-dimensional radiative-convective model with ion chemistry. As one of the main results, we show that, despite the intensity of EEP-induced ionization rates, polar mesospheric ozone cannot be destroyed by EEP in summer in the presence of UV radiation. In winter time, the maximum ozone depletion, at altitude of about 80 km, can reach up to 80% during strong geomagnetic disturbances. In fall and spring, the maximum ozone depletion is less intense and can reach 20% during strong geomagnetic disturbances. Linear relation of EEP induced maximum mesospheric ozone depletion depending on geomagnetic disturbances and seasons have been obtained. [ABSTRACT FROM AUTHOR]

This paper formulates the cosmic ray--driven electron- induced reaction as a universal mechanism to provide a quantitative understanding of global ozone depletion. Based on a proposed electrostatic bonding mechanism for charge- induced adsorption of molecules on surfaces and on the measured dissociative electron transfer (DET) cross sections of ozone- depleting substances (ODSs) adsorbed on ice, an analytical equation is derived to give atmospheric chlorine atom concentration: ... where Φe is the prehydrated electron ... flux produced by cosmic ray ionization on atmospheric particle surfaces, ... is the surface coverage of an ODS, and ... is the ODS's effective DET coefficient that is the product of the DET cross section, the lifetimes of surface-trapped ... and ..., and the particle surface area density. With concentrations of ODSs as the sole variable, our calculated results of time-series ozone depletion rates in global regions in the 1960s, 1980s, and 2000s show generally good agreement with observations, particularly with ground- based ozonesonde data and satellite-measured data over Antarctica and with satellite data in a narrow altitude band at 13 to 20 km of the tropics. Good agreements with satellite data in the Arctic and midlatitudes are also found. A previously unreported effect of denitrification on ozone loss is found and expressed quantitatively. But this equation overestimates tropospheric ozone loss at northern midlatitudes and the Arctic, likely due to increased ozone production by the halogen chemistry in polluted regions. The results render confidence in applying the equation to achieve a quantitative understanding of global ozone depletion. [ABSTRACT FROM AUTHOR]

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Previous studies have demonstrated a dynamical linkage between the ozone and stratospheric polar vortex strength, but only a few have mentioned the persistence of the anomalous vortex. This study uses the complete ensemble empirical mode decomposition with adaptive noise to decompose the winter stratospheric northern annular mode (NAM) variabilities into relatively low frequencies (>4 months) and high frequencies (

Willy Ramos,1,2 Ericson L Gutierrez,1,3 Jhony A De La Cruz-Vargas,1 Jesús Díaz,4 Jorge Hurtado,2 Gerardo Ronceros,2 Esther de Vries5 1Instituto de Investigaciones en Ciencias Biomédicas (INICIB), Universidad Ricardo Palma, Lima, Perú; 2Instituto de Investigaciones Clínicas, Universidad Nacional Mayor de San Marcos, Lima, Perú; 3Centro Nacional de Salud Pública, Instituto Nacional de Salud, Lima, Perú; 4Universidad Católica Santo Toribio de Mogrovejo, Chiclayo, Perú; 5Departamento de Epidemiologia Clínica y Bioestadística, Pontificia Universidad Javeriana, Bogotá, ColombiaCorrespondence: Willy Ramos, Instituto de Investigaciones en Ciencias Biomédicas (INICIB), Universidad Ricardo Palma, Av. Alfredo Benavides 5440, Santiago de Surco, Lima, 15039, Perú, Email willymh98@hotmail.comObjective: To determine if exposure to atmospheric ozone disruption and other factors are associated with photodermatoses in the high-altitude pediatric population in Peru.Materials and Methods: A cross-sectional study based on data obtained from studies of dermatological diseases among the population exposed to mine tailings in Peru which included children under the age of 18 in 6 population centers located over 2500 meters above sea level (m.a.s.l). We evaluated the presence of photodermatoses and possible associated factors obtaining the adjusted odds ratio (aOR) and confidence intervals (CI).Results: 594 children below the age of 18 participated in this study, 53.0% girls, the average age was 10.4 ± 4.1 years. 51.3% were exposed to a mini hole in the ozone layer, 60.1% resided at an altitude over 3500 m.a.s.l and 51.9% presented cutaneous manifestations of atopy upon physical examination. The prevalence of photodermatoses was 64.8%, of which the most frequent were actinic prurigo (49.3%), pityriasis alba (18.5%) and actinic cheilitis (4.4%). The multivariate analysis found that residing in a region exposed to the mini hole in the ozone layer (aOR = 4.23; CI 95%: 2.32– 7.72) and residing at an altitude over 3500 m.a.s.l (aOR = 2.76; CI 95%: 1.57– 4.86) were both independent associated factors to photodermatoses.Conclusion: A high prevalence of photodermatoses exists among the pediatric population living at high-altitude in Peru. Residing in a region exposed to a mini hole in the ozone layer and residing over 3500 m.a.s.l constituted associated factors.Keywords: ultraviolet rays, ozone depletion, high-altitude, children, adolescents

Methyl halides (CH3Cl, CH3Br, and CH3I) are ozone-depleting substances. Biomass burning (BB) is an important source of methyl halides. The temporal variations and global spatial distribution of BB methyl halide emissions are unclear. Thus, global methyl halide emissions from BB during 2003–2021 were estimated based on satellite data. A significant decreasing trend (p

Abstract In recent decades, the two polar regions have exhibited strikingly different changes, with much greater warming in the Arctic than the Antarctic. However, the warming asymmetry between the two polar regions is quite small during the second half of the twentieth century. By using a multi-member ensemble of simulations with the Community Earth System Model, this study investigates the relative contributions of greenhouse gases, aerosol, and ozone forcings to the responses of Arctic and Antarctic surface temperature during 1955–2000. Results show that both the greenhouse gases- and aerosols-induced changes are greater in the Arctic than in the Antarctic, yet they are opposite and act to balance each other, leaving a limited warming in the Arctic and hence a small bipolar asymmetry. Using a radiative kernel, feedback analysis reveals that both greenhouse gases and aerosol forcings influence the polar surface temperature through albedo feedback related to sea ice changes and lapse rate feedback related to strong surface temperature inversion. The ozone forcing can hardly excite any surface temperature changes over the polar regions even in the Antarctic with the strongest ozone depletion, which is due to a cancellation between the cooling effect from radiative forcing and cloud radiative feedback, and the warming effect from lapse rate feedback and enhanced atmospheric heat transport from lower latitudes.

Enhanced UV-B radiation resulting from stratospheric ozone depletion has been documented both globally and on the Qinghai-Tibet Plateau in China. The response of Kobresia humilis, an important alpine meadow plant species, to enhanced UV-B radiation was experimentally investigated at the Haibei Alpine Meadow Ecosystem Research Station (37°29′–37°45′ N, 101°12′–101°23′ E; alt. 3200 m). K. humilis was exposed to UV-B radiation including ambient UV-B and enhanced UV-B (simulating a 14% reduction in the ozone layer) in a randomized design with three replications of each treatment. Enhanced UV-B radiation resulted in a significant increase of both leaf area and fresh weight chlorophyll and carotenoid but had no effect on UV-B absorbing pigments. Similarly, enhanced UV-B radiation did not significantly change the photosynthetic O2 elevation rate while leaf thickness, width, and length significantly increased (p < 0.01). The enhanced UV-B radiation was associated with 2–3 days earlier flowering and a larger number of flowers per spikelet. The enhanced UV-B generally resulted in larger leaves and more flowers but earlier phenology. In summary, these findings suggest that alpine species of K. humilis have adapted to the strong solar UV-B radiation intensity presented on the Qinghai-Tibet Plateau, but the interspecies differences and their influence on trophic level should be more concerning. [ABSTRACT FROM AUTHOR]

Energetic electron precipitation (EEP) into the atmosphere are considered to play an important role in the natural forcing of the ozone variability and dynamics of the middle atmosphere during magnetospheric and geomagnetic disturbances. Energetic electrons from the radiation belt spill out into the atmosphere during geomagnetic disturbances and cause additional ionization rates in the polar middle atmosphere. These rates of induced atmospheric ionization lead to the formation of radicals in ion-molecular reactions at the heights of the mesosphere with the formation of reactive compounds of odd nitrogen groups NOy and odd hydrogen groups HOx. These compounds are involved in catalytic reactions that destroy ozone. The percentage of ozone destruction can depend not only intensity of EEP but also on season where it happens. In this work, we study mesospheric ozone depletion depending on seasons and precipitating energetic electrons with energies from keV up to relativistic energies about 1 MeV, based on the NOAA POES satellites observations in 2003. For estimation ozone deplation we use a one-dimensional radiative-convective model with ion chemistry. As one of the main results, we show that, despite the intensity of EEP-induced ionization rates, polar mesospheric ozone cannot be destroyed by EEP in summer in the presence of UV radiation. In winter time, the maximum ozone depletion, at altitude of about 80 km, can reach up to 80% during strong geomagnetic disturbances. In fall and spring, the maximum ozone depletion is less intense and can reach 20% during strong geomagnetic disturbances. Linear relation of EEP induced maximum mesospheric ozone depletion depending on geomagnetic disturbances and seasons have been obtained.

Detailed examination of the impact of modern space launches on the Earth's atmosphere is crucial, given booming investment in the space industry and an anticipated space tourism era. We develop air pollutant emissions inventories for rocket launches and re‐entry of reusable components and debris in 2019 and for a speculative space tourism scenario based on the recent billionaire space race. This we include in the global GEOS‐Chem model coupled to a radiative transfer model to determine the influence on stratospheric ozone (O3) and climate. Due to recent surge in re‐entering debris and reusable components, nitrogen oxides from re‐entry heating and chlorine from solid fuels contribute equally to all stratospheric O3 depletion by contemporary rockets. Decline in global stratospheric O3 is small (0.01%), but reaches 0.15% in the upper stratosphere (∼5 hPa, 40 km) in spring at 60–90°N after a decade of sustained 5.6% a−1 growth in 2019 launches and re‐entries. This increases to 0.24% with a decade of emissions from space tourism rockets, undermining O3 recovery achieved with the Montreal Protocol. Rocket emissions of black carbon (BC) produce substantial global mean radiative forcing of 8 mW m−2 after just 3 years of routine space tourism launches. This is a much greater contribution to global radiative forcing (6%) than emissions (0.02%) of all other BC sources, as radiative forcing per unit mass emitted is ∼500 times more than surface and aviation sources. The O3 damage and climate effect we estimate should motivate regulation of an industry poised for rapid growth. Plain Language Summary: It is imperative that we understand the current and future risks to Earth's atmosphere posed by pollution from rocket launches and re‐entry heating of reusable and discarded rocket parts and historical debris. Rockets, unlike other anthropogenic pollution sources, emit gaseous and solid chemicals directly into the upper atmosphere. We compile inventories of these chemicals from rocket launches in 2019 and projections of future growth and speculative space tourism activity. We incorporate these in a 3D atmospheric chemistry model to simulate the impact on climate and the protective stratospheric ozone layer. We find that loss of ozone due to current rockets is small, but that routine space tourism launches may undermine progress made by the Montreal Protocol in reversing ozone depletion in the Arctic springtime upper stratosphere. The BC (or soot) particles from rockets are also of great concern, as these are almost five hundred times more efficient at warming the atmosphere than all other sources of soot combined. These findings demonstrate an urgent need to develop environmental regulation to mitigate damage from this rapidly growing industry. Key Points: Air pollutant emission inventory for current space sector and future tourism input to a coupled chemistry and radiative transfer modelUpper stratospheric Arctic ozone loss from launch chlorine and re‐entry nitrogen oxide emissions undermines Montreal Protocol successWarming efficiency of space tourism (soot) emissions about 500‐times greater than surface and aircraft sources of soot [ABSTRACT FROM AUTHOR]

The global warming potential of Ozone‐depleting substances (ODS) has long been known to be thousands of times larger than the one of CO2, but their climate impacts as greenhouse gases, i.e. unmediated ozone depletion, has received relatively little attention. Focusing on the period 1955–2005, we here present results from offline radiative forcing (RF) calculations from a global chemistry climate model. Using realistic distributions of ODS and consistent stratospheric ozone, we show that ODS dominate the adjusted stratospheric warming of the lower stratosphere, where CO2 has little radiative impact. We also show that the global mean RF of stratospheric ozone only cancels a fraction of the RF of ODS, leaving an important ODS contribution to anthropogenic forcing. Finally we show that the RF of ODS opposes Arctic amplification, its equator‐to‐pole gradient being larger than the one of CO2. Plain Language Summary: In the decades following World War II, organic compounds of chlorine and bromine, widely used in refrigerators and spray cans, entered the atmosphere and led to the formation of the ozone hole. However, these compounds, are also powerful greenhouse gases and are important for global warming. Here we study their warming effects in the stratosphere and at the surface. We find that, over the period 1955–2005, they were the dominant atmospheric gas warming the tropical lower stratosphere, where CO2 is largely inactive; that their surface warming effect (their radiative forcing) amounted to approximately one third of the CO2 value, even after accounting for reductions due to the ozone depletion they induce; and, finally that, even more than CO2, their radiative effects warmed the equatorial more the polar regions and, as such, cannot be the reason why the Arctic is warming more than the rest of the planet. Key Points: The radiative effect of Ozone‐depleting substances on lower stratospheric temperatures is the largest of all well‐mixed greenhouse gasesTheir radiative forcing is only partially (∼25%) canceled by the stratospheric ozone depletion they induceTheir radiative forcing is weaker at the pole than at the equator opposing Arctic amplification even more than CO2 forcing [ABSTRACT FROM AUTHOR]

Using an environmental scanning electron microscope, we quantified for the first time aerosol‐sized salt particles formed during the sublimation of sea ice as a function of temperature and concentration. The sublimation temperature of the ice is a dominating physical factor to determine the size of the residua: Below −20°C, micron‐sized pieces of salt emerge, whereas above the temperature large chunks of salt are detected. Another such aspect influencing the distribution of sizes in salt particles is the concentration: Micron‐sized particles are observed exclusively at salinities below 3.5 psu, while below 0.085 psu particles with a median smaller than 6 μm arise from sea ices at any subzero temperature. Moreover, when a chunk of salt sublimes at less than −30°C to be dried and warmed later, a large number of sub‐micron crystals will appear. We relate our findings to the production of the polar atmospheric sea salt aerosols. Plain Language Summary: In polar regions, saline ices on sea ice or at coastal areas are thought to be a direct source of chemical compounds and sea salt aerosols; these salty aerosols are important to polar atmospheric chemistry and global climate for various reasons, such as that they affect atmospheric radiation in both a direct and an indirect manner. However, the exact location of the salts within the ice, together with the temperature and concentration dependence of the size and number density of the salt particles formed, was previously poorly understood and not well quantified. We therefore utilized a unique electron microscope to observe the structural changes occurring when saline ices sublime to create salt particles. Our experiments showed that small salt particles, proxies of sea salt aerosols, are preferably generated from low‐concentrated ices and at low temperatures. These microscopic observations provide direct laboratory evidence to the proposed mechanism of sea salt aerosol production from sublimating saline ice and snow and may help us to fit the missing piece of information into the puzzle of polar spring ozone depletion and bromine explosion events. Key Points: The size distribution and numerical density of salt particles formed from sublimating salty ices were quantified for the first timeMicrometer‐sized particles arise from low salinity ices (<3.5 psu) below −30 °C; in 0.085 psu ices, they form at any subzero temperature>100 μm particles are produced by sublimation above −21 °C in ices above 0.85 psu, and at any temperature in those exceeding 35 psu [ABSTRACT FROM AUTHOR]

In recent decades, the two polar regions have exhibited strikingly different changes, with much greater warming in the Arctic than the Antarctic. However, the warming asymmetry between the two polar regions is quite small during the second half of the twentieth century. By using a multi-member ensemble of simulations with the Community Earth System Model, this study investigates the relative contributions of greenhouse gases, aerosol, and ozone forcings to the responses of Arctic and Antarctic surface temperature during 1955–2000. Results show that both the greenhouse gases- and aerosols-induced changes are greater in the Arctic than in the Antarctic, yet they are opposite and act to balance each other, leaving a limited warming in the Arctic and hence a small bipolar asymmetry. Using a radiative kernel, feedback analysis reveals that both greenhouse gases and aerosol forcings influence the polar surface temperature through albedo feedback related to sea ice changes and lapse rate feedback related to strong surface temperature inversion. The ozone forcing can hardly excite any surface temperature changes over the polar regions even in the Antarctic with the strongest ozone depletion, which is due to a cancellation between the cooling effect from radiative forcing and cloud radiative feedback, and the warming effect from lapse rate feedback and enhanced atmospheric heat transport from lower latitudes. [ABSTRACT FROM AUTHOR]

While the Montreal Protocol is reducing stratospheric ozone loss, recent increases in some ozone depleting substance (ODS) emissions have been identified that may impact southern hemisphere climate systems. In this study, we discuss characteristics of the 2018 and 2019 Antarctic ozone holes using surface insitu, satellite and reanalysis data to gain a better understanding of recent ozone variability. These ozone holes had strongly contrasting characteristics. In 2018, the Antarctic stratospheric vortex was relatively stable and cold in comparison to most years of the prior decade. This resulted in a large and persistent ozone hole that ranked in the upper-tercile of metrics quantifying Antarctic ozone depletion. In contrast, strong stratospheric warming in the spring of 2019 curtailed the development of the ozone hole, causing it to be anomalously small and of similar size to ozone holes in the 1980s. As known from previous studies, the ability of planetary waves to propagate into the stratosphere at high latitudes is an important factor that influences temperatures of the polar vortex and the overall amount of ozone loss in any particular year. Disturbance and warming of the vortex by strong planetary wave activity were the dominant factors in the small 2019 ozone hole. In contrast, planetary wave disturbances to the vortex in the winter–spring of 2018 were much weaker than in 2019. These results increase our understanding of the impact of Montreal Protocol controls on ODS and the effects of Antarctic ozone on the southern hemisphere climate system.

Methyl bromide (CH3Br) is an ozone depleting trace gas that is now mainly emitted from natural sources. Roughly 80% of anthropogenic production of CH3Br was phased‐out in response to the Montreal Protocol on Substances that Deplete the Ozone Layer beginning in 1999 and atmospheric levels of CH3Br have declined considerably since. Here we use surface measurements of CH3Br from NOAA's global air sampling network, along with a six‐box atmosphere/ocean model to explore interannual variability in atmospheric CH3Br mole fractions. We find that CH3Br mole fractions are strongly correlated with the El Niño Southern Oscillation (ENSO) phenomenon, but variability in winds, sea surface temperature, and biological production during ENSO are unlikely to drive the observed changes in atmospheric CH3Br directly. Rather, the results indicate that ENSO‐driven changes to biomass burning are an important cause of the observed interannual CH3Br variability. Plain Language Summary: Methyl bromide (CH3Br) is a trace gas known to destroy stratospheric ozone. Atmospheric mole fractions of CH3Br have declined substantially over time because of Montreal Protocol controls on production of this ozone‐depleting gas. What remained unexplained were the substantial temporary variations observed in the measurement record. Here we find that those variations are related to El Niño Southern Oscillation (ENSO) events, and the increased burning during the warm phase of ENSO is determined to be the most likely cause of these interannual changes. Key Points: Interannual variability in the global atmospheric methyl bromide (CH3Br) mole fraction is strongly correlated with the El Niño Southern Oscillation (ENSO) phenomenonChanges in the ocean (sea surface temperature and winds) during ENSO are unlikely to cause the observed variability in atmospheric CH3Br mole fractionThe majority of interannual variability in atmospheric CH3Br mole fraction is explained by ENSO‐driven fire emissions [ABSTRACT FROM AUTHOR]

The catalytic depletion of Antarctic stratospheric ozone is linked to anthropogenic emissions of chlorine and bromine. Despite its larger ozone-depleting efficiency, the contribution of oceanemitted iodine to ozone hole chemistry has not been evaluated, due to the negligible iodine levels previously reported to reach the stratosphere. Based on the recently observed range (0.77 ± 0.1 parts per trillion by volume [pptv]) of stratospheric iodine injection, we use the Whole Atmosphere Community Climate Model to assess the role of iodine in the formation and recent past evolution of the Antarctic ozone hole. Our 1980-2015 simulations indicate that iodine can significantly impact the lower part of the Antarctic ozone hole, contributing, on average, 10% of the lower stratospheric ozone loss during spring (up to 4.2% of the total stratospheric column). We find that the inclusion of iodine advances the beginning and delays the closure stages of the ozone hole by 3 d to 5 d, increasing its area and mass deficit by 11% and 20%, respectively. Despite being present in much smaller amounts, and due to faster gas-phase photochemical reactivation, iodine can dominate (∼73%) the halogen-mediated lower stratospheric ozone loss during summer and early fall, when the heterogeneous reactivation of inorganic chlorine and bromine reservoirs is reduced. The stratospheric ozone destruction caused by 0.77 pptv of iodine over Antarctica is equivalent to that of 3.1 (4.6) pptv of biogenic very short-lived bromocarbons during spring (rest of sunlit period). The relative contribution of iodine to future stratospheric ozone loss is likely to increase as anthropogenic chlorine and bromine emissions decline following the Montreal Protocol. [ABSTRACT FROM AUTHOR]

The expansion of Antarctic sea ice since 1979 in the presence of increasing greenhouse gases remains one of the most puzzling features of current climate change. Some studies have proposed that the formation of the ozone hole, via the Southern Annular Mode, might explain that expansion, and a recent paper highlighted a robust causal link between summertime Southern Annular Mode (SAM) anomalies and sea ice anomalies in the subsequent autumn. Here we show that many models are able to capture this relationship between the SAM and sea ice, but also emphasize that the SAM only explains a small fraction of the year‐to‐year variability. Finally, examining multidecadal trends, in models and in observations, we confirm the findings of several previous studies and conclude that the SAM–and thus the ozone hole–are not the primary drivers of the sea ice expansion around Antarctica in recent decades. Plain Language Summary: Unlike its Arctic counterpart, sea ice around Antarctica has been growing since 1979, even as the levels of carbon dioxide in the atmosphere have increased. Given that the ozone hole formed over the South Pole around the same time, one is led to ask whether the ozone hole may be responsible for the growth of Antarctic sea ice (recall that there is no ozone hole over the North Pole). In this study, looking at both models and observations, we show that the ozone hole is capable of affecting the surface winds and these, in turn, can make sea ice expand. However, the magnitude of this effect is small. Also since the ozone hole started healing after the year 2000, while Antarctic sea ice kept expanding, we conclude that ozone depletion is not the main reason for the expansion of Antarctic sea ice in recent decades. Key Points: Many CMIP5 models are able to capture the observed seasonal correlation between summertime Southern Annular Mode (SAM) and Antarctic sea ice extentThe SAM, however, only explains 15 of the year‐to‐year sea ice extent variability in the fall, in both models and observationsSAM trends, and ozone depletion, are not the primary drivers of the observed Antarctic sea ice expansion in the last four decades [ABSTRACT FROM AUTHOR]

Due to the depletion in the ozone layer, solar UV radiation at the earth's surface is increasing, impacting economically important plants. The current study assesses the effects of UV radiation on germination, growth, chlorophyll content and fresh and dry weight of Brassica rapa L. and Eruca sativa L. Some seeds of Brassica rapa L. and Eruca sativa L. were placed in petri plates, and were exposed to UV light for 30, 60 and 120 mins daily. The source of UV light was a UV box having a UV Tube. The UV exposure on the seeds reduced the germination percentage in both species. The germination percentage in control was recorded as 19.35%, while it was 18.65% in 30min and 19.00% in 120min exposures. Root and shoot growth of the seedlings was markedly reduced by increasing UV radiation. The shoot length was 2.40mm in control, 2.75mm in 30min, 1.50mm in 60min and 1.60mm in 120min of exposure to the UV light. The root length in control was 1.38mm, 0.90mm in 30min, 1.00mm in 60min and 1.17mm in 120min exposure. The UV irradiations affected the chlorophyll contents positively, and therefore, the total quantity of chlorophyll content increased, compared to the control. The chlorophyll content in the control was 6.90 (µmol m-2) of leaf area while treatment showed 8.08 (µmol m-2) in 30min, 8.01 (µmol m-2) in 60min and 10.01 (µmol m-2) in 120min exposure. In both species, fresh and dry weights were decreased, as compared to the control set. The fresh weight of the control was 0.85g, 0.65g in 30min, 0.78g in 60min and 0.61g in 120min exposure. The dry weight of the control was recorded to be 0.70g, 0.60g in 30min, 0.62g in 60min and 0.50g in 120min exposure. It was concluded that ultraviolet radiation decreased the radicle and plumule lengths in Brassica rapa and Eruca sativa while increasing their chlorophyll content. [ABSTRACT FROM AUTHOR]

Enhanced UV-B radiation resulting from stratospheric ozone depletion has been documented both globally and on the Qinghai-Tibet Plateau in China. The response of Kobresia humilis, an important alpine meadow plant species, to enhanced UV-B radiation was experimentally investigated at the Haibei Alpine Meadow Ecosystem Research Station (37°29′–37°45′ N, 101°12′–101°23′ E; alt. 3200 m). K. humilis was exposed to UV-B radiation including ambient UV-B and enhanced UV-B (simulating a 14% reduction in the ozone layer) in a randomized design with three replications of each treatment. Enhanced UV-B radiation resulted in a significant increase of both leaf area and fresh weight chlorophyll and carotenoid but had no effect on UV-B absorbing pigments. Similarly, enhanced UV-B radiation did not significantly change the photosynthetic O2 elevation rate while leaf thickness, width, and length significantly increased (p < 0.01). The enhanced UV-B radiation was associated with 2–3 days earlier flowering and a larger number of flowers per spikelet. The enhanced UV-B generally resulted in larger leaves and more flowers but earlier phenology. In summary, these findings suggest that alpine species of K. humilis have adapted to the strong solar UV-B radiation intensity presented on the Qinghai-Tibet Plateau, but the interspecies differences and their influence on trophic level should be more concerning.

In this paper, an experimental investigation on the performance of vapor-compression based milk refrigerator using R290 as refrigerant is carried out. Milk refrigerator is driven by solar photovoltaic. R290 is considered to be the next generation refrigerant due to its excellent thermodynamic properties, cost, and environmental characteristics. The experimental set up consists of milk refrigerator that includes variable speed R290 DC compressor and solar PV modules along with batteries. Various performance parameters i.e. coefficient of performance, solar coefficient of performance, cooling capacity, and energy consumption are investigated for the different room temperature using variable speed mode. The results obtained from the tests are presented and discussed.

Australian wildfires burning from December 2019 to January 2020 injected approximately 0.9 Tg of smoke into the stratosphere; this is the largest amount observed in the satellite era. A comparison of numerical simulations to satellite observations of the plume rise suggests that the smoke mass contained 2.5% black carbon. Model calculations project a 1 K warming in the stratosphere of the Southern Hemisphere midlatitudes for more than 6 months following the injection of black‐carbon containing smoke. The 2020 average global mean clear sky effective radiative forcing at top of atmosphere is estimated to be −0.03 W m−2 with a surface value of −0.32 W m−2. Assuming that smoke particles coat with sulfuric acid in the stratosphere and have similar heterogeneous reaction rates as sulfate aerosol, we estimate a smoke‐induced chemical decrease in total column ozone of 10–20 Dobson units from August to December in mid‐high southern latitudes. Plain Language Summary: The 2019–2020 Australian bushfires injected a large amount of smoke that rose well into the stratosphere due to absorption of solar energy. A climate model is used to simulate the plume rise, transport, chemical, and climate impacts of the smoke from these massive bushfires. Simulations suggest that the smoke remained in the stratosphere for all of 2020 and that it measurably warmed the stratosphere by about 1–2 K for more than 6 months. The smoke particles were transported to high latitudes in the Southern Hemisphere and assuming similar heterogeneous reaction rates as sulfate aerosol should have produced about 4%–6% loss of the total column at high southern latitudes. Key Points: The 2019–2020 Australian wildfire injected about 0.9 Tg smoke containing 2.5% black carbon into the stratosphereClimate model simulations indicate that the smoke warmed the Southern Hemisphere stratosphere by 1 K for more than 6 monthsModel calculations estimate a decrease in ozone of 10–20 Dobson units from August to December at mid‐high southern latitudes [ABSTRACT FROM AUTHOR]

Surface westerly winds in the Southern Hemisphere have intensified over the past few decades, primarily in response to the formation of the Antarctic ozone hole, and there is intense debate on the impact of this on the ocean's circulation and uptake and redistribution of atmospheric gases. We used measurements of chlorofluorocarbon-12 (CFC-12) made in the southern oceans in the early 1990s and mid- to late 2000s to examine changes in ocean ventilation. Our analysis of the CFC-12 data reveals a decrease in the age of subtropical subantarctic mode waters and an increase in the age of circumpolar deep waters, suggesting that the formation of the Antarctic ozone hole has caused large-scale coherent changes in the ventilation of the southern oceans.

We use a three‐dimensional chemical transport model and satellite observations to investigate Arctic ozone depletion in winter/spring 2019/20 and compare with earlier years. Persistently, low temperatures caused extensive chlorine activation through to March. March‐mean polar‐cap‐mean modeled chemical column ozone loss reached 78 DU (local maximum loss of ∼108 DU in the vortex), similar to that in 2011. However, weak dynamical replenishment of only 59 DU from December to March was key to producing very low (<220 DU) column ozone values. The only other winter to exhibit such weak transport in the past 20 years was 2010/11, so this process is fundamental to causing such low ozone values. A model simulation with peak observed stratospheric total chlorine and bromine loading (from the mid‐1990s) shows that gradual recovery of the ozone layer over the past 2 decades ameliorated the polar cap ozone depletion in March 2020 by ∼20 DU. Plain Language Summary: Ozone depletion in the polar stratosphere is caused by chlorine and bromine species which are activated by low temperatures. Chlorine and bromine are transported to the stratosphere following the surface emission of ozone‐depleting substances (ODSs). While springtime ozone depletion in the Antarctic is almost always large, it is much more variable in the Arctic due to warmer temperatures and more disturbed stratospheric dynamics. Using a three‐dimensional atmospheric chemical transport model and satellite observations, we show that the very low ozone columns observed in March 2020 were a consequence of large chemical destruction and weaker‐than‐normal replenishment by transport. These very low ozone levels are, by some measures, record values despite 2 decades of decreasing stratospheric chlorine and bromine through controls of the Montreal Protocol. Had the meteorology of 2019/20 occurred 2 decades ago, the ozone loss would have been notably larger. The Arctic stratospheric dynamics for 2019/20 are extreme relative to the past 2 decades but fit a compact relationship that links column ozone variations over Arctic and Antarctic winters. Key Points: Large mean Arctic (>63°N) chemical ozone destruction in 2019/20 of 78 DU, similar to other extreme cold winters in the past 2 decadesAnomalously weak wintertime dynamical replenishment of only ∼60 DU contributed strongly to the very low observed ozone column in MarchOzone recovery caused 20 DU less mean Arctic ozone loss in March 2020 than would have occurred with stratospheric halogens at 1995 levels [ABSTRACT FROM AUTHOR]

A suite of chemistry‐climate model simulations, forced by pairs of anthropogenic forcings [comprising greenhouse gases (GHGs), ozone depleting substances (ODSs), or aerosols], were employed to investigate whether the high‐latitude Southern Hemisphere (SH) circulation response to these forcings is linearly additive, a common assumption in attribution studies. We find that the geographical pattern of sea‐level pressure (SLP) response to a combination of GHGs and ODSs is linearly additive. However, we find significant differences in the SLP response when combining GHGs and aerosols compared to the sum of the individual forcings, a non‐additivity that is currently masked by the dominance of the ODSs forcing. This non‐linearity also results in changes to the SH split jet. These results were obtained using a coupled chemistry‐climate model, indicating that the non‐linear response is due to chemical interactions between the forcing agents. As such, future simulations investigating a post‐ozone hole Southern Hemisphere climate should consider this chemical interaction. [ABSTRACT FROM AUTHOR]

Aviation alters the composition of the atmosphere globally and can thus drive climate change and ozone depletion. The last major international assessment of these impacts was made by the Intergovernmental Panel on Climate Change (IPCC) in 1999. Here, a comprehensive updated assessment of aviation is provided. Scientific advances since the 1999 assessment have reduced key uncertainties, sharpening the quantitative evaluation, yet the basic conclusions remain the same. The climate impact of aviation is driven by long-term impacts from CO2 emissions and shorter-term impacts from non-CO2 emissions and effects, which include the emissions of water vapour, particles and nitrogen oxides (NOx). The present-day radiative forcing from aviation (2005) is estimated to be 55 mW m−2 (excluding cirrus cloud enhancement), which represents some 3.5% (range 1.3–10%, 90% likelihood range) of current anthropogenic forcing, or 78 mW m−2 including cirrus cloud enhancement, representing 4.9% of current forcing (range 2–14%, 90% likelihood range). According to two SRES-compatible scenarios, future forcings may increase by factors of 3–4 over 2000 levels, in 2050. The effects of aviation emissions of CO2 on global mean surface temperature last for many hundreds of years (in common with other sources), whilst its non-CO2 effects on temperature last for decades. Much progress has been made in the last ten years on characterizing emissions, although major uncertainties remain over the nature of particles. Emissions of NOx result in production of ozone, a climate warming gas, and the reduction of ambient methane (a cooling effect) although the overall balance is warming, based upon current understanding. These NOx emissions from current subsonic aviation do not appear to deplete stratospheric ozone. Despite the progress made on modelling aviation's impacts on tropospheric chemistry, there remains a significant spread in model results. The knowledge of aviation's impacts on cloudiness has also improved: a limited number of studies have demonstrated an increase in cirrus cloud attributable to aviation although the magnitude varies: however, these trend analyses may be impacted by satellite artefacts. The effect of aviation particles on clouds (with and without contrails) may give rise to either a positive forcing or a negative forcing: the modelling and the underlying processes are highly uncertain, although the overall effect of contrails and enhanced cloudiness is considered to be a positive forcing and could be substantial, compared with other effects. The debate over quantification of aviation impacts has also progressed towards studying potential mitigation and the technological and atmospheric tradeoffs. Current studies are still relatively immature and more work is required to determine optimal technological development paths, which is an aspect that atmospheric science has much to contribute. In terms of alternative fuels, liquid hydrogen represents a possibility and may reduce some of aviation's impacts on climate if the fuel is produced in a carbon-neutral way: such fuel is unlikely to be utilized until a ‘hydrogen economy’ develops. The introduction of biofuels as a means of reducing CO2impacts represents a future possibility. However, even over and above land-use concerns and greenhouse gas budget issues, aviation fuels require strict adherence to safety standards and thus require extra processing compared with biofuels destined for other sectors, where the uptake of such fuel may be more beneficial in the first instance.

An enhanced UV-B radiation (5.0 kJ m−2) was supplied before, during, and after Magnaporthe oryzae infection. The effects of single and compound stress of the UV-B radiation and M. oryzae on the resistance physiology and gene expression of rice leaves were examined. Results revealed that UV-B radiation given before M. oryzae infection (UV-B → M.) significantly increased the pathogenesis-related proteins (PRs) activities of phenylalanine ammonialyase (PAL), lipoxygenase (LOX), chitinase (CHT), and β-1,3-glucanase, the resistance-related substances (flavonoids and total phenols) content, and resistance-related genes (OsPAL and OsCHT) expression, thereby improving the disease resistance of rice leaves. Simultaneous exposure to UV-B radiation and M. oryzae (UV-B/M.) significantly increased the OsLOX2 expression and the PRs activities. Exposure to UV-B radiation after M. oryzae infection (M. → UV-B) decreased the flavonoid content, did not improve the PRs activity, and increased OsLOX2 expression. Compound treatments of UV-B → M., UV-B/M., and M. → UV-B reduced the disease index by 62.3%, 40.2%, and 26.6%, respectively, indicating UV-B radiation inhibited the occurrence of M. oryzae disease, but its inhibitory effect weakened when it was provided after M. oryzae infection. Hence, rice responded to the compound stress of UV-B radiation and M. oryzae through a resistance-related physiological mechanism associated with the sequence of stress occurrence.

We assess the effective radiative forcing due to ozone‐depleting substances using models participating in the Aerosols and Chemistry and Radiative Forcing Model Intercomparison Projects (AerChemMIP, RFMIP). A large intermodel spread in this globally averaged quantity necessitates an "emergent constraint" approach whereby we link the radiative forcing to ozone declines measured and simulated during 1979–2000, excluding two volcanically perturbed periods. During this period, ozone‐depleting substances were increasing, and several merged satellite‐based climatologies document the ensuing decline of total‐column ozone. Using these analyses, we find an effective radiative forcing of −0.05 to 0.13 W m−2. Our best estimate (0.04 W m−2) is on the edge of the "likely" range given by the Fifth Assessment Report of IPCC of 0.03 to 0.33 W m−2 but is in better agreement with two other literature results. Plain Language Summary: Chloroflourocarbons and other compounds involved in ozone depletion are also powerful greenhouse gases, but their contribution to global warming is reduced due to the cooling effect of the ozone loss which they induce. Models informing an upcoming climate report disagree on the ozone loss and thus on the climate influence of these gases. Here we use observed ozone loss to reduce the resultant uncertainty in their overall climate influence and infer a smaller warming influence of these substances than was considered likely in a 2013 climate report. The result implies a smaller benefit to climate due to their phase‐out, mandated under the Montreal Protocol, than would have been the case under previous understanding. Key Points: Effective radiative forcing of ozone‐depleting substances, as discerned from CMIP6 simulations, spans a large rangeUsing an emergent constraint approach, our new estimate is consistent with observational climatologies of total‐column ozoneThis range implies a smaller forcing than the estimate provided by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [ABSTRACT FROM AUTHOR]

Environmental problems were not among the core issues for the United Nations at its creation in 1945. In the 1970s, however, they created a crescendo of public concern as the threats posed by toxic chemicals, large-scale destruction of natural ecosystems, and the loss of species became visible and were obviously linked to human activity. Pollution, it was clear, did not stop at national borders and solutions required common effort. As part of the special issue on "The United Nations at Seventy-Five: Looking Back to Look Forward," this essay explores how, as the only institution equipped to identify global problems and generate collective action toward their resolution, the UN became the platform for creating multilateral environmental agreements, convening global conferences, and mobilizing national and international effort through a progressively larger number of institutions at the national and international level to guide decisions and influence behavior. We have moved the environmental needle in terms of information, institutions, and awareness. Yet, many environmental problems persist, some are getting worse, and new challenges and, indeed, crises are emerging. [ABSTRACT FROM AUTHOR]

The knowledge of atmospheric chemistry has explained several reactions that occur in atmosphere regarding volatile organic compounds (VOCs). In this original paper, computational kinetic study was carried out on atmospheric oxidation reaction mechanism of 1-fluoro-2-methoxypropane (CH 3 CH(OCH 3)CFH 2) with OH/ClO radicals using DFT/M06-2X/6–311++G∗∗ method. To improve the results, DFT/M06-2X/6–311++G(2df,2p) single-point calculations were performed on the reacting species involved. The Monte Carlo search on the investigating hydrofluoroether (H 3 CCH(OCH 3)CFH 2) showed nine conformers with the lowest global minimum conformer being considered for this study. The reaction proceeded via four (4) reaction routes which led to dehydrogenation in each cases of the radical (OH/ClO) used. The total rate for dehydrogenation reaction of H 3 CCH(OCH 3)CFH 2 with OH/ClO radicals is 9.13 ∗ 103 s−1 and 1.23 ∗ 106 s−1 at 298 K which is in agreement with the available experimental rates recorded by Healthfield et al. (1998), Kazuaki Tokuhashi et al. (2000). Also, in each radical cases, thermodynamics parameters, the major and minor products' heat of formation were computed with potential energy surfaces (PES) for the reactions constructed at absolute temperature of 298 K. [ABSTRACT FROM AUTHOR]