The study finds a *minor and declining* stratospheric influence on surface ozone increase in China over 2015–2022, especially for direct deep intrusion events. It reports that detectable ozone with stratospheric origins makes up only 1.6–2.2% of surface ozone in China on an annual basis.

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. High latitudes has been caused by increasing abundances of chlorine and bromine species, which are derived from long-lived surface-emitted halogenated gases, so-called ozone-depleting substances (ODSs). Increasing atmospheric concentrations of greenhouse gases, such as carbon dioxide, methane and nitrous oxide, have large potential to perturb stratospheric ozone in different ways, but their future evolutions, and hence impacts, are uncertain.

Using IASI satellite observations, the authors analyzed lower-tropospheric ozone over the North China Plain for 2008–2016. They report that a possible reduction of stratosphere–troposphere exchanges was the main contributor to the observed negative trend, rather than a sign of large stratospheric ozone depletion over China.

The document says China’s FY-3A, FY-3B, and FY-3C satellites are used to detect ozone vertical profiles from the global atmosphere. This is evidence of observation capacity, not of a documented significant depletion of stratospheric ozone over China from pollution.

Halogen-induced ozone depletion events have often been observed in the stratosphere and in tropospheric polar regions in springtime. Halogens are atmospheric oxidants that affect ozone (O3) concentrations and the oxidative capacity of the troposphere. The report discusses midlatitude stratospheric ozone depletion associated with industrial halogens but notes that the most prominent depletion has historically been in polar regions, with midlatitude effects generally smaller and globally distributed rather than focused on one country.

This study focuses on tropospheric and surface ozone, noting that in the past decade "ozone (O3) pollution has become a severe environmental problem in China's major cities" and that all ozone metrics examined show increasing trends over 2014–2020. The paper attributes the rise primarily to photochemical production from NOx and VOC precursors and changes in emissions, meteorology, and chemistry, without identifying stratospheric ozone depletion over China as the cause. The emphasis is on surface pollution rather than depletion of the stratospheric ozone layer.

The abstract states that "Methyl Chloride (CH3Cl) is the largest source of stratospheric chlorine, which has a significant impact on the depletion of the stratospheric ozone layer." It reports that "China's anthropogenic CH3Cl emissions have increased significantly, from 34.1 ± 11.6 Gg/yr in 2000 to 128.5 ± 26.5 Gg/yr in 2018 with a slight decrease to 124.9 ± 26.0 Gg/yr in 2020," and that "China's contribution to global anthropogenic emissions of CH3Cl reached almost 50%." The authors conclude that these emissions "presented a potential increasing impact on the depletion of the ozone layer and global warming."

This paper states that China established a national ozone observation network in 2013 and that satellite remote sensing can monitor ozone variability at regional to global scales. It does not report evidence that stratospheric ozone over China is significantly depleted; instead, it frames ozone research in terms of surface monitoring and satellite-derived products.

We report for the first time that halogens substantially enhance the total atmospheric oxidation capacity in polluted areas of China, typically 10% to 20% (up to 87% in winter) and mainly by significantly increasing OH level. Surface O3 is slightly increased by ~2% (annual average) by halogens in northern China and is decreased in other regions (by as much as −16%). The results reveal the significant control of halogens on atmospheric oxidation, the levels of oxidants and air pollutants in China, which potentially contributes to close the current gap between the observation and simulation of atmospheric oxidation in China.

The authors reconstruct emissions of ozone-depleting substances (ODSs) and HFC substitutes in China and report that "the ODS and HFC emissions in China increased from 3 kt yr−1 in 1980 to 248 kt yr−1 in 2020." By 2020, they estimate "10.8 and 5.8 (4.8–6.9) Mt of cumulative CFC-11-eq emissions of ODSs" from banks and emissions respectively. The paper assesses environmental impacts in terms of contributions to global ozone depletion potential and climate forcing but does not present evidence of a localized, uniquely large depletion of the stratospheric ozone column over China compared with global trends; instead, Chinese ODS emissions are treated as part of the global ODS budget governed by the Montreal Protocol.

The paper describes CH3Cl as "an important ozone-depleting substance" and notes that "China's anthropogenic CH3Cl emissions rapidly increased from 34.1 Gg/yr in 2000 to 124.9 Gg/yr in 2020." It identifies key sectors: "Chemical production (10.7% in 2000 totals; 37.1% in 2020 totals) and solvent use (6.5% in 2000 totals; 35.4% in 2020 totals) became the main sources of anthropogenic CH3Cl emissions in China." The authors state that anthropogenic CH3Cl emissions in China "have shown an increasing trend in the past two decades" and that this has "a potential increasing impact on the depletion of the ozone layer."

Halogens, including chlorine, bromine, and iodine, are recognized for their significant impact on atmospheric oxidants such as hydroxyl radical (OH), peroxy radical (HO2), ozone (O3), and nitrate radical (NO3) in the troposphere, which subsequently affects air quality. The study finds that halogens can elevate the annual OH radical levels by as much as 16.4% while reducing NO3 by up to 45.3%. Additionally, anthropogenic chlorine raises both O3 and NO3 production rates by affecting their precursors, while oceanic halogens diminish NO3 production rates and directly deplete ozone. Halogens are recognized as significant contributors to ozone depletion events in the stratosphere, but the analysis here focuses on tropospheric coastal pollution over eastern China.

Increasing surface ozone (O3) concentrations has emerged as a key air pollution problem in many urban regions worldwide in the last decade. By applying this new approach, we show that for most urban regions of China, the O3 formation is currently associated with a volatile organic compound (VOC)-limited regime. Synergetic VOC and NOx reduction and increasingly strict anthropogenic VOC control should be the primary focus at the present stage for controlling O3 pollution in China. The paper discusses surface and near-tropospheric ozone pollution driven by NOx–VOC chemistry, rather than stratospheric ozone depletion over China.

Nocturnal oxidation driven by nitrate radicals is an important but poorly understood process in atmospheric chemistry, affecting the lifetimes of NO and ozone and particulate pollution levels. We show that nitrate radicals have undergone strong increases in China during 2014–2019 but exhibited modest decreases in the United States and the European Union. Accelerated night-time oxidation has shortened the lifetime of summer NOx in China by 30% during 2014–2019. This change will strongly affect ozone formation and has policy implications for the joint control of ozone and fine particulate pollution.

NOAA reports that an international assessment found "China has become a hot spot of present-day surface ozone pollution" and that people in China "breathe air thick with the lung-damaging pollutant ozone two to six times more often" than in the US, Europe, Japan, or South Korea. The article discusses high numbers of days over China's national ozone air-quality standard and notes that every surface ozone metric "rose continuously in China over the last five years" examined. This piece deals with ground-level (tropospheric) ozone pollution, not depletion of stratospheric ozone above China.

The article reviews recent trends in China's ozone pollution and notes that increasing surface ozone has "emerged as a key air pollution problem" in many urban regions, including China. Using diagnostic ratios, the authors show that in most urban regions of China, ozone formation is currently "associated with a volatile organic compound (VOC)-limited regime" and discuss how coordinated reductions in VOC and NOx emissions are needed to curb ozone. The focus is on photochemical production and control of surface ozone, with no indication in the analysis that stratospheric ozone over China is being significantly depleted by domestic pollution beyond its contribution to the global ODS budget.

Reporting on a study in Geophysical Research Letters, Yale E360 states that "Despite being banned in 2010, about 40,000 tons of carbon tetrachloride, an ozone-depleting compound, are still emitted into the atmosphere every year." The article says that an international team "tracked down the source of nearly half of the emissions to eastern China" and that ongoing emissions from industrialized areas in eastern China "account for half the global total from 2009 to 2016." It adds that the researchers also found "evidence of a possible new source of emissions in China’s Shandong province after 2012."

This case study says stratospheric intrusion can aggravate summertime ozone pollution in eastern China and that stratospheric ozone can contribute to near-surface ozone during specific events. The paper also states that the contribution of stratospheric intrusion to surface ozone was estimated at 5.7%–18.8% in prior work it cites.

The study focuses on surface (tropospheric) ozone and notes that "the increasing ozone trend in eastern China has continued through 2019, driven by both anthropogenic emissions and meteorological trends." It explains that a 15% decrease in PM2.5 in 2017–2019 "may be driving the continued anthropogenic increase in ozone, as well as unmitigated emissions of volatile organic compounds (VOCs)." The authors emphasize that "VOC emission reductions, as targeted by Phase 2 of the Chinese Clean Air Action Plan, are needed to reverse the increase in ozone" and that there is "a sustained anthropogenic ozone increase over the [North China Plain] over the 2013–2019 record."

A new study finds that the western United States reduced its production of ozone-forming pollutants by a whopping 21 percent between 2005 and 2010. Over China, ozone increased about seven percent in the mid-troposphere. The researchers found two causes: first, Chinese emissions of ozone-forming pollutants increased 21 percent during these years; second, an unusually large amount of ozone drifted down from the stratosphere as the result of several periodic, natural cycles, including an El Niño event in 2009–10.

This modeling study examines surface ozone in China and states that "O3 pollution has worsened despite substantial reductions of anthropogenic NOx emissions." It finds that interactions between "transboundary O3 and domestic precursors accounted for 44% to 49% of surface O3 levels across Eastern China" during a studied autumn episode. The authors argue that this interplay between background ozone and domestic anthropogenic emissions "fundamentally shaped the ambient O3 formation regime," challenging the view that background ozone is chemically static and redefining the controllable portion of ozone pollution.

The paper notes that "In China, emissions of ozone (O3)-producing pollutants have been targeted for mitigation to reduce O3 pollution. However, the observed O3 decrease is slower than/opposite to expectations affecting the health of millions of people." Using a "de-weathering" technique, it quantifies summer ozone trends across 31 urban regions and analyzes how changes in NOx, anthropogenic VOCs, and PM2.5 affect ozone. The authors find that in some regions "VOC reductions are the main driver of O3 decreases," while in others "decreasing PM2.5 results in enhanced O3 formation," highlighting the complex response of surface ozone to anthropogenic emission changes.

While PM2.5 pollution is falling, harmful ground-level ozone pollution is on the rise, especially in large cities. The researchers found that particulate matter acts like a sponge for the radicals needed to generate ozone pollution, sucking them up and preventing them from producing ozone. But the rapid reduction of PM2.5 dramatically altered the chemistry of the atmosphere, leaving more radicals available to produce ozone. Results from this study suggest that extra efforts are needed to reduce NOx and VOC emissions in order to stem the tide of ozone pollution.

In a section on ozone-depleting substances, the State Department notes that under the Montreal Protocol nations agreed to phase out production of such substances but that "scientists identified an increase of emissions of the phased-out, ozone-depleting substance CFC-11 from Eastern China from 2014 to 2017." The document frames this as non-compliance with treaty obligations and calls for improved Chinese monitoring and enforcement. It does not claim that these increased CFC‑11 emissions have uniquely depleted the stratospheric ozone layer above China, but rather that they threaten global ozone-layer recovery.

The UNEP page explains that the Montreal Protocol is a global agreement to "protect the ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS)." It highlights that the Protocol covers chlorofluorocarbons (CFCs) and other ODS used in many countries, including China, and notes that as a result of worldwide ODS reductions, the ozone layer is projected to recover by mid-21st century. The description underscores that ozone depletion is a global, not country-localized, phenomenon driven by worldwide ODS emissions that mix throughout the stratosphere, rather than causing isolated, significantly depleted ozone specifically over individual nations like China.

This JGR study quantifies the role of soil versus anthropogenic nitrogen oxide emissions in China's surface ozone. It reports that "Warm-season soil NOx emissions (SNOx) account for 23%–27% of total NOx emissions in China during 2015–2022" and evaluates their contribution to ozone formation relative to anthropogenic sources. The authors highlight that both anthropogenic and natural (soil) NOx control strategies can influence surface ozone, illustrating the multiple contributors to ozone pollution in the lower atmosphere over China.

The release says Chinese satellite observations can retrieve ozone vertical profiles and integrated stratospheric column ozone. It provides capability context for observing ozone distribution, but it does not itself show significant depletion of stratospheric ozone over China due to pollution.

Stratospheric ozone depletion is classically associated with halogenated ozone-depleting substances and polar chemistry, not with ordinary urban air pollution. Pollution in China is much more directly linked to surface and tropospheric ozone formation than to large-scale stratospheric ozone loss.