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Percentage recovery (return to 1980 values) by 2050 from four model simulations with different chlorine loading for various ozone-hole metrics.
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The Antarctic ozone hole is decreasing in size but this recovery will be affected by atmospheric variability and any unexpected changes in chlorinated source gas emissions. Here, using model simulations, we show that the ozone hole will largely cease to occur by 2065 given compliance with the Montreal Protocol. If the unusual meteorology of 2002 is...
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... is demonstrated in Fig. 5 for run R2000, R2000_NoVSLS, R2000_CFC11_B and R2000_CFC11_67. This approach means that the extent of recovery at any time can be compared on a relative scale (see Table 3 for these values in 2050). Presentation of the results in this way avoids the issue of return dates being strongly affected by the shape of the ozone recovery trajectory, and that, under some circumstances, the atmosphere may not return to 1980 values at all. ...Similar publications
The Umkehr observations over Kyiv (Ukraine) and Antarctic Peninsula areas were processed for the first time to retrieve and analyse the vertical distribution of ozone. The Umkehr observations have been pre-processed using the UMK92 software package proposed by the World Ozone and UV-radiation Data Centre (WOUDC). The set of the calculated vertical...
A rare disturbance of the stratospheric Antarctic polar vortex in September 2019 led to a significantly higher than usual polar total ozone column. We use assimilation of ozone, HCl, and N2O data from the Microwave Limb Sounder with the Global Earth Observing System (GEOS) Constituent Data Assimilation System driven by reanalysis meteorology to stu...
In refrigeration technology, there is a need for alternative refrigerants that need to fulfil several requirements, such as low (or no) global warming potential, flammability, ozon depletion potential, and toxicity. While there are many substances available that could potentially be used as refrigerants, only relatively few fulfil all of the requir...
Plain Language Summary
Iodine has the potential to cause stratospheric ozone depletion. Small satellites (<10 kg) in low Earth orbit require electric propulsion to prolong their time in orbit, and there is strong interest in replacing the rare gas propellant (Xe or Kr) with I2. Here we estimate the potential impact of thermosphere iodine injection...
Sudden stratospheric warmings (SSWs) are associated with rapid rise in temperature in a short period of time in the polar vortex and reversal of the zonal winds in major warming conditions. Although SSWs are primarily driven by the planetary waves emanating from the troposphere, the exact reasons and factors responsible for the wave forcing are sti...
Citations
... The model contains a detailed description of stratospheric chemistry, including heterogeneous reactions on sulfate aerosols and PSCs. Here the model was forced using European center for medium-range weather forecasts ERA5 winds and temperatures (Hersbach et al., 2020) and run with a resolution of 2.8°× 2.8°with 32 levels from the surface to ∼60 km, as in Dhomse et al. (2019). The surface mixing ratios of long-lived source gases (e.g., CFCs, HCFCs, CH 4 , N 2 O) were taken from WMO (2018) scenario A1 and upper tropospheric chlorinated very short-lived substances (VSLS; e.g. ...
We use trace gas profiles from Atmospheric Chemistry Experiment ‐ Fourier Transform Spectrometer (ACE‐FTS) satellite measurements and the TOMCAT three‐dimensional chemical transport model to diagnose stratospheric trends in O3, HCl and N2O. We find that the 2004–2021 ACE‐FTS trends exhibit a clear lower stratosphere (LS) interhemispheric asymmetry with positive (negative) O3 and N2O (HCl) trends in the Southern Hemisphere (SH), and trends of opposite sign in the Northern Hemisphere (NH). The trends are larger for the shorter time period of 2004–2018. TOMCAT qualitatively agrees with the ACE‐FTS LS N2O and HCl trends, confirming that transport variability drives such patterns, despite some discrepancies for O3. An additional model simulation is used to quantify the sensitivity of O3 to long‐term changes in chlorine and bromine and thus determine the chemical contribution of the spatially varying halogen trends to both observed and modeled O3 trends. Overall, the recent dynamically induced variation in mid‐latitude LS halogen abundance has, through chemical feedback, accentuated the O3 recovery signal in the SH and delayed it in the NH, reflecting the enhanced dynamical variability of the NH. These results further indicate the complexities that exist in the search for the signal of ozone recovery in the mid‐latitude LS.
... Although both UVA and UVB can cause damage to organisms, the shorter wavelength UVB is more damaging to cellular and subcellular structures (Bajgar et al., 2021;De Gruijl, 2002). In the early 1980s, anthropogenic stratospheric ozone depletion gained much international attention for the potential impact that increased UVR levels would have on ecosystems (Dhomse et al., 2019;IPCC, 1988;Jackson, 2007;Madronich et al., 1995;McKenzie et al., 2011;Williamson et al., 2014). Although the extreme UVR levels projected under a 'no-action' scenario were largely avoided by the 1987 Montreal Protocol, UVB levels did increase by approximately 5-10% at mid-latitudes since anthropogenic ozone depletion began (depending on season and location; Barnes et al., 2019). ...
Ultraviolet radiation (UVR) is a pervasive factor that has shaped the evolution of life on Earth. Ambient levels of UVR mediate key biological functions but can also cause severe lethal and sublethal effects in a wide range of organisms. Furthermore, UVR is a powerful modulator of the effects of other environmental factors on organismal physiology, such as temperature, disease, toxicology and pH, among others. This is critically important in the context of global change, where understanding the effects of multiple stressors is a key challenge for experimental biologists. Ecological physiologists rarely afford UVR discussion or include UVR in experimental design, even when it is directly relevant to their study system. In this Commentary, we provide a guide for experimental biologists to better understand if, when, and how UVR can be integrated into experimental designs to improve the ecological realism of their experiments.
... Following this discovery, alarm was raised by policymakers involved in the MP process that these renewed emissions could cause a delay in the recovery of the ozone layer (e.g. Dhomse et al., 2019). Extensions of these observations for a further 3 years (Montzka et al., 2021;Park et al., 2021) show that these renewed emissions of CFC-11 appear to have greatly declined. ...
We summarise current important and well-established open issues related to the depletion of stratospheric ozone and discuss some newly emerging challenges. The ozone layer is recovering from the effects of halogenated source gases due to the continued success of the Montreal Protocol despite recent renewed production of controlled substances and the impact of uncontrolled very short-lived substances. The increasing atmospheric concentrations of greenhouse gases, such as carbon dioxide, methane (CH4) and nitrous oxide (N2O), have large potential to perturb stratospheric ozone in different ways, but their future evolutions, and hence impacts, are uncertain. Ozone depletion through injection of smoke particles has been observed following recent Australian wildfires. Further perturbations to the ozone layer are currently occurring through the unexpected injection of massive amounts of water vapour from the Hunga Tonga–Hunga Ha'apai volcano in 2022. Open research questions emphasise the critical need to maintain, if not expand, the observational network and to address the impending “satellite data gap” in global, height-resolved observations of stratospheric trace gases and aerosols. We will, in effect, be largely blind to the stratospheric effects of similar wildfire and volcanic events in the near future. Complex Earth system models (ESMs) being developed for climate projections have the stratosphere as an important component. However, the huge computational requirement of these models must not result in an oversimplification of the many processes affecting the ozone layer. Regardless, a hierarchy of simpler process models will continue to be important for testing our evolving understanding of the ozone layer and for providing policy-relevant information.
... The approach of offsetting, through a reduction in emission or production of an ODS, the cumulative ozone depletion arising from unexpected or illicit emissions after weighting those emissions by the ODP, is supported by the near-linear relationships between cumulative emissions of a particular long-lived ODS and stratospheric ozone impacts from that ODS, both globally and over the Antarctic (Keeble et al., 2020;Fleming et al., 2020;Dhomse et al., 2019) as summarized in the WMO et al. (2021). This is because the impacts on stratospheric ozone of an emission roughly scale by the amount of chlorine (Cl) released into the stratosphere, all other factors (aerosol loading, etc.) being equal, and so can be applied to CFC-12, CTC, and other ODS species Keeble et al., 2020;WMO et al., 2021). ...
... This estimate is based on the "bank scenario", which assumes that CFC-11 emissions began increasing in 2012 above those expected under the reference WMO A1 scenario, peak around 77 Gg yr −1 in 2015-2017, and then decline sharply through 2100. While the end date of unreported production is unclear, the report states that "In the fourth scenario, CFC-11 emissions were estimated based onDhomse et al. (2019), which constructs an emissions scenario curve based on initial rapid increase in CFC-11 emissions and slower release from accumulated CFC-11 banks. This scenario first takes the estimate of 13 Gg yr −1 in new emissions due to unreported production and assumes an immediate production release rate of 15 % followed by 3.5 % yr −1 . ...
By phasing out production and consumption of most ozone-depleting substances (ODSs), the Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal Protocol) has avoided consequences of increased ultraviolet (UV) radiation and will restore stratospheric ozone to pre-1980 conditions by mid-century, assuming compliance with the phaseout. However, several studies have documented an unexpected increase in emissions and suggested unreported production of trichlorofluoromethane (CFC-11) and potentially other ODSs after 2012 despite production phaseouts under the Montreal Protocol. Furthermore, because most ODSs are powerful greenhouse gases (GHGs), there are significant climate protection benefits in collecting and destroying the substantial quantities of historically allowed production of chemicals under the Montreal Protocol that are contained in existing equipment and products and referred to as ODS “banks”. This technical note presents a framework for considering offsets to ozone depletion, climate forcing, and other environmental impacts arising from occurrences of unexpected emissions and unreported production of Montreal Protocol controlled substances, as recently experienced and likely to be experienced again. We also show how this methodology could be applied to the destruction of banks of controlled ODSs and GHGs or to halon or other production allowed under a Montreal Protocol Essential Use Exemption or Critical Use Exemption. Further, we roughly estimate the magnitude of offset each type of action could provide for ozone depletion, climate, and other environmental impacts that Montreal Protocol Parties agree warrant remedial action.
... Oram et al. (2017) also reported high concentrations of Cl-VSLS in tropical regions over the western Pacific Ocean, where they can be rapidly uplifted to the upper troposphere. Additionally, it is shown that keeping the Cl-VSLS flux constant (compared to a zero Cl-VSLS flux scenario) will delay the return date of total column ozone to 1980 levels by approximately seven years Dhomse et al., 2019;Laube et al., 2022). Long-lived chlorinated ozone depleting substances (ODSs; i.e., CFCs, HCFCs, etc.) have been overall successfully controlled under the Montreal Protocol. ...
Chlorinated very short‐lived substances (Cl‐VSLS) are ubiquitous in the troposphere and can contribute to the stratospheric chlorine budget. In this study, we present measurements of atmospheric dichloromethane (CH2Cl2), tetrachloroethene (C2Cl4), chloroform (CHCl3), and 1,2‐dichloroethane (1,2‐DCA) obtained during the National Aeronautics and Space Administration (NASA) Atmospheric Tomography (ATom) global‐scale aircraft mission (2016–2018), and use the Community Earth System Model (CESM) updated with recent chlorine chemistry to further investigate their global tropospheric distribution. The measured global average Cl‐VSLS mixing ratios, from 0.2 to 13 km altitude, were 46.6 ppt (CH2Cl2), 9.6 ppt (CHCl3), 7.8 ppt (1,2‐DCA), and 0.84 ppt (C2Cl4) measured by the NSF NCAR Trace Organic Analyzer (TOGA) during ATom. Both measurements and model show distinct hemispheric gradients with the mean measured Northern to Southern Hemisphere (NH/SH) ratio of 2 or greater for all four Cl‐VSLS. In addition, the TOGA profiles over the NH mid‐latitudes showed general enhancements in the Pacific basin compared to the Atlantic basin, with up to ∼18 ppt difference for CH2Cl2 in the mid troposphere. We tagged regional source emissions of CH2Cl2 and C2Cl4 in the model and found that Asian emissions dominate the global distributions of these species both at the surface (950 hPa) and at high altitudes (150 hPa). Overall, our results confirm relatively high mixing ratios of Cl‐VSLS in the UTLS region and show that the CESM model does a reasonable job of simulating their global abundance but we also note the uncertainties with Cl‐VSLS emissions and active chlorine sources in the model. These findings will be used to validate future emission inventories and to investigate the fast convective transport of Cl‐VSLS to the UTLS region and their impact on stratospheric ozone.
... Here we have performed a TOMCAT simulation (ERA5), which is forced with ECMWF ERA5 (Hersbach et al., 2020) reanalysis (e.g. Dhomse et al., 2019;Li et al., 2022a). The ERA5 reanalysis has been released by ECMWF to supersede ERA-Interim, which covered January 1979 to August 2019, with more and newer observations assimilated into ERA5. ...
Accurate quantification of long-term trends in stratospheric ozone can be challenging due to their sensitivity to natural variability, the quality of the observational datasets, and non-linear changes in forcing processes as well as the statistical methodologies. Multivariate linear regression (MLR) is the most commonly used tool for ozone trend analysis; however, the complex coupling in many atmospheric processes can make it prone to the issue of over-fitting when using the conventional ordinary-least-squares (OLS) approach. To overcome this issue, here we adopt a regularized (ridge) regression method to estimate ozone trends and quantify the influence of individual processes. We use the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) merged dataset (v2.7) to derive stratospheric ozone profile trends for the period 1984–2020. Besides SWOOSH, we also analyse a machine-learning-based satellite-corrected gap-free global stratospheric ozone profile dataset from a chemical transport model (ML-TOMCAT) and output from a chemical transport model (TOMCAT) simulation forced with European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis.
For 1984–1997, we observe smaller negative trends in the SWOOSH stratospheric ozone profile using ridge regression compared to OLS. Except for the tropical lower stratosphere, the largest differences arise in the mid-latitude lowermost stratosphere (>4 % per decade difference at 100 hPa). From 1998 and the onset of ozone recovery in the upper stratosphere, the positive trends estimated using the ridge regression model (∼1 % per decade near 2 hPa) are smaller than those using OLS (∼2 % per decade). In the lower stratosphere, post-1998 negative trends with large uncertainties are observed and ridge-based trend estimates are somewhat smaller and less variable in magnitude compared to the OLS regression. Aside from the tropical lower stratosphere, the largest difference is around 2 % per decade at 100 hPa (with ∼3 % per decade uncertainties for individual trends) in northern mid-latitudes. For both time periods the SWOOSH data produce large negative trends in the tropical lower stratosphere with a correspondingly large difference between the two trend methods. In both cases the ridge method produces a smaller trend. The regression coefficients from both OLS and ridge models, which represent ozone variations associated with natural processes (e.g. the quasi-biennial oscillation, solar variability, El Niño–Southern Oscillation, Arctic Oscillation, Antarctic Oscillation, and Eliassen–Palm flux), highlight the dominance of dynamical processes in controlling lower-stratospheric ozone concentrations. Ridge regression generally yields smaller regression coefficients due to correlated explanatory variables, and care must be exercised when comparing fit coefficients and their statistical significance across different regression methods.
Comparing the ML-TOMCAT-based trend estimates with the ERA5-forced model simulation, we find ML-TOMCAT shows significant improvements with much better consistency with the SWOOSH dataset, despite the ML-TOMCAT training period overlapping with SWOOSH only for the Microwave Limb Sounder (MLS) measurement period. The largest inconsistencies with respect to SWOOSH-based trends post-1998 appear in the lower stratosphere where the ERA5-forced model simulation shows positive trends for both the tropics and the mid-latitudes. The large differences between satellite-based data and the ERA5-forced model simulation confirm significant uncertainties in ozone trend estimates, especially in the lower stratosphere, underscoring the need for caution when interpreting results obtained with different regression methods and datasets.
... These emissions were likely due to new production and use [79]. They were initially of concern as they would delay recovery of ozone [80] and make a small but significant contribution to global warming [81]. The emissions appear to have been eliminated [82][83][84] and likely did not have a significant effect on dates of recovery of the ozone hole [85][86][87][88]. ...
This assessment provides a comprehensive update of the effects of changes in stratospheric ozone and other factors (aerosols, surface reflectivity, solar activity, and climate) on the intensity of ultraviolet (UV) radiation at the Earth’s surface. The assessment is performed in the context of the Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments and Adjustments. Changes in UV radiation at low- and mid-latitudes (0–60°) during the last 25 years have generally been small (e.g., typically less than 4% per decade, increasing at some sites and decreasing at others) and were mostly driven by changes in cloud cover and atmospheric aerosol content, caused partly by climate change and partly by measures to control tropospheric pollution. Without the Montreal Protocol, erythemal (sunburning) UV irradiance at northern and southern latitudes of less than 50° would have increased by 10–20% between 1996 and 2020. For southern latitudes exceeding 50°, the UV Index (UVI) would have surged by between 25% (year-round at the southern tip of South America) and more than 100% (South Pole in spring). Variability of erythemal irradiance in Antarctica was very large during the last four years. In spring 2019, erythemal UV radiation was at the minimum of the historical (1991–2018) range at the South Pole, while near record-high values were observed in spring 2020, which were up to 80% above the historical mean. In the Arctic, some of the highest erythemal irradiances on record were measured in March and April 2020. For example in March 2020, the monthly average UVI over a site in the Canadian Arctic was up to 70% higher than the historical (2005–2019) average, often exceeding this mean by three standard deviations. Under the presumption that all countries will adhere to the Montreal Protocol in the future and that atmospheric aerosol concentrations remain constant, erythemal irradiance at mid-latitudes (30–60°) is projected to decrease between 2015 and 2090 by 2–5% in the north and by 4–6% in the south due to recovering ozone. Changes projected for the tropics are ≤ 3%. However, in industrial regions that are currently affected by air pollution, UV radiation will increase as measures to reduce air pollutants will gradually restore UV radiation intensities to those of a cleaner atmosphere. Since most substances controlled by the Montreal Protocol are also greenhouse gases, the phase-out of these substances may have avoided warming by 0.5–1.0 °C over mid-latitude regions of the continents, and by more than 1.0 °C in the Arctic; however, the uncertainty of these calculations is large. We also assess the effects of changes in stratospheric ozone on climate, focusing on the poleward shift of climate zones, and discuss the role of the small Antarctic ozone hole in 2019 on the devastating “Black Summer” fires in Australia. Additional topics include the assessment of advances in measuring and modeling of UV radiation; methods for determining personal UV exposure; the effect of solar radiation management (stratospheric aerosol injections) on UV radiation relevant for plants; and possible revisions to the vitamin D action spectrum, which describes the wavelength dependence of the synthesis of previtamin D3 in human skin upon exposure to UV radiation.
Graphical abstract
... The ozone depletion in Antarctica created a unique scenario to investigate photochemical processes in both the polar stratosphere and troposphere. Most projections agree that the ozone layer will recover to the pre-1970 level around 2100 73 . Two important outcomes derived from our measurements and data processing: (1) intense interactions of sea salt particles with snowpack geochemical byproducts pointedly increased chlorine depletion from sea salt. ...
Since the early 1980s, the Antarctic environment has served as a natural field laboratory for researchers to investigate the effects of stratospheric ozone depletion, which has resulted in increased surface ultraviolet radiation levels. However, its effective threats still present gaps. We report new pieces of evidence of increased ultraviolet radiation impacting West Antarctica sea salt aerosols. Salt aerosols, particularly in the Southern Ocean Sea, play an important role in the radiative earth balance. To disclose the molecular details of sea salt aerosols, we used a synchrotron-based multi-element microscopic speciation of individual microparticles (Scanning Transmission X-ray Microscopy with Near-Edge X-ray Absorption Fine Structure Spectroscopy combined with Computer-Controlled Scanning Electron Microscopy). Here we identified substantial abundances of chlorine-enriched aerosols in sea salt generated by photolytic products, whereas ice core records revealed increased chlorine depletion from the onset of ozone depletion. Our findings reveal that modern sea salt modification has no Holocene precedent.
... Trichlorofluoromethane (CFC-11) is one of the most significant ODSs that still contribute to the distraction of stratospheric ozone (CFC-11; Ref. 357). Concentrations of CFC-11 had been declining significantly since the implementation of the Montreal Protocol, but between 2012 and 2018 unexpected deceleration in the rate of decline was observed because of unreported production (358)(359)(360)(361)(362). If this unreported production were sustained it would delay the recovery of stratospheric ozone and would also imply unauthorized dichlorodifluoromethane (CFC-12) coproduction. ...
Solar ultraviolet-B (UV-B) radiation has played a crucial role in the evolution of life on Earth. UV exposure presents both risks and benefits to humans. Optimal UV-B exposure behaviors, that ensure balance between the risks and benefits of exposure to UV-B depend both on environmental and physiological factors and cannot be easily determined. The present review provides the current state of knowledge relative to the effects of UV-B radiation to humans. The physical mechanisms that control the
levels of solar UV-B radiation at the Earth’s surface are also discussed. A comprehensive review of the studies reporting on current trends in the levels of solar UV-B radiation at the surface and model projections of its future levels is examined and reveals the important role of man-made climatic changes in its evolution.
The review provides evidence that despite the success of the
Montreal Protocol, the future evolution of the levels of solar UV-B radiation at the Earth’s surface has important uncertainties caused by the expected changes in our climate. Therefore, it is recommended that the usual precautionary measures to protect from excess exposure of humans to solar UV-B radiation should continue to apply in the decades to come.
... [Amos et al., 2020: 9961. o.] Más becslések szerint ennél akár egy évtizeddel is tovább tarthat e folyamat különösen amiatt, hogy a nemzetközi kötelezettségvállalások ellenére 2010 után "illegális" légköri freonkibocsátások történtek [Dhomse, 2019]. ...
(Publication: in Hungarian + English summary:) Our common planetary home is affected by various hazardous environmental processes resulting from human activities. Such processes became gradually global during the past century and include especially the environmental releases of toxic heavy metals, hazardous chemicals and waste, atmospheric emissions of ozone-depleting substances and greenhouse gases. Their consequences have significant impacts on the living conditions of present and future generations. The author of this book presents the emergence and escalation of these environmental problems, the history of their recognition, the development of the international scientific and political cooperation, their most essential outcomes, including the various multilateral programmes and agreements. Based on the extensive review and analysis of these issues, the main conclusions and lessons are also drawn. (The book includes hundreds of literature references and pertinent quotes from many authors and international documents.)
