Airborne Observations of CFCs Over Hebei Province, China in Spring 2016

Benish, Sarah E.; Salawitch, R. J.; Ren, Xinrong; He, Hao; Dickerson, Russell R.

doi:10.1029/2021jd035152

Cited by 12 publications

(5 citation statements)

References 77 publications

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“…This was the case with unexpected emissions of CFC-11 after 2012 (Benish et al, 2021;Lickley et al, 2020;Park et al, 2018;Rigby et al, 2019), where allowing for production uncertainty in the banks modeling framework over this time period resulted in posterior production estimates that were non-zero following 2010, and larger posterior bank values than what was inferred by assuming zero production uncertainty and full compliance with the Protocol following 2010.…”

Section: Resultsmentioning

confidence: 99%

“…For the 2022 SAOD report, new production of controlled substances not in compliance with the Montreal Protocol was considered; this new production is included implicitly through increases to both atmospheric concentrations and explicitly through the bank size of the affected ODS. These updates have been made in light of evidence of unreported production of halocarbons in recent years (Benish et al, 2021;Lickley et al, 2022;Park et al, 2018;Rigby et al, 2019;Montzka et al, 2021;Park et al, 2021;Sherry et al, 2018) as well as during the 1980s in the Soviet Union at an amount that accounted for ~20% of global production of CFC-11 (Gamlen et al, 1986), suggesting historical production may have been consistently underestimated in earlier SAOD reports. Production of CCl4 has similarly been consistently underestimated in the SAODs (SPARC, 2016).…”

Section: Resultsmentioning

confidence: 99%

“…We henceforth refer to these five reports as the 2006; 2010; 2014; 2018; and 2022 SAODs. Specifically, we consider how the delay has been affected by the consistent underestimate of the global production of ODSs (Benish et al, 2021;Lickley et al, 2022;Park et al, 2018;Rigby et al, 2019;Montzka et al, 2021;Park et al, 2021;Sherry et al, 2018), as modeled through banks and feedstocks, and observed in part by measured mole fractions following each SAODs publication. In addition, we consider the role of changes in ODS atmospheric lifetime assumptions that affect future atmospheric abundances (SPARC, 2013), and variations in the scientific understanding of the best underlying approach used to compute EESC (Engel et al, 2018;Newman et al, 2007).…”

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confidence: 99%

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The return to 1980 stratospheric halogen levels: A moving target in ozone assessments from 2006 to 2022

Lickley,

Daniel,

McBride

et al. 2024

Preprint

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Abstract. The international scientific assessment of ozone depletion is prepared every four years to support decisions made by the Parties to the Montreal Protocol. In each assessment an outlook of ozone recovery time is provided. The year when equivalent effective stratospheric chlorine (EESC) returns to the level found in 1980 is an important metric for the recovery of the ozone layer. Over the past five assessments, the expected date for the return of EESC to the 1980 level, for mid-latitudes, has been delayed, from year 2049 in the 2006 assessment to 2066 in the 2022 assessment, which represents a delay of 17 years over a 16-year assessment period. Here, we quantify the primary drivers that have delayed the expected EESC recovery date between each of these assessments. We find that by using identical EESC formulations the delay between the 2006 and 2022 assessment’s expected return of EESC to 1980 levels is shortened to 12.6 years. Of this delay, bank calculation methods account for ~4 years, changes in the assumed atmospheric lifetime for certain ODSs account for ~3.5 years, an under-estimate of the emission of CCl4 accounts for ~3 years, and updated historical mole fraction estimates of ODSs account for ~1 year. Since some of the underlying causes of these delays are amenable to future controls (e.g. capture of ODSs from banks and limitations on future feedstock emissions), it is important to understand the reasons for the delays in expected recovery date of stratospheric halogens.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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The return to 1980 stratospheric halogen levels: A moving target in ozone assessments from 2006 to 2022

Lickley,

Daniel,

McBride

et al. 2024

Preprint

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“…Southeastern China has undergone significant economic and industrial growth over the past decades, thus holding great importance in investigating CFC-11 emissions. However, ambient levels of CFC-11 in southeastern China have been poorly quantified [12,[15][16][17][18][19][20][21]. Previous studies allow emission estimates only based on short-term campaigns [18,22].…”

Section: Introductionmentioning

confidence: 99%

Observations and emission constraints of trichlorofluoromethane (CFC-11) in southeastern China: first-year results from a new AGAGE station

Chen,

Yao,

et al. 2024

Environ. Res. Lett.

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The recovery of the ozone layer relies on decreasing atmospheric mixing ratios of ozone-depleting substances (ODSs), including chlorofluorocarbons (CFCs). A significant decline in the mixing ratio of trichlorofluoromethane (CFC-11 or CCl 3 F ), the second most abundant CFC, has been observed since the mid-1990s. However, a slowdown in the decline after 2012 indicates a rise in emissions, particularly in Eastern Asia. Ground-based observations are lacking in southeastern China, limiting a thorough evaluation of CFC-11 levels and emissions in this region. A new Advanced Global Atmospheric Gases Experiment background station was established at Xichong (XCG), Shenzhen, China, to provide high-frequency continuous in situ observations. The annual mean CFC-11 mixing ratio, recorded from May 2022 to April 2023, is 221.64 ± 2.29 ppt. When compared with a monthly (MHD) or daily (MLO) observation, this value is found to be 0.45% to 5.36% higher than the northern hemispheric background. With the inverse modeling and interspecies correlation method, we estimate CFC-11 emissions in southeastern China between 1.23 ± 0.25 Gg yr−1 and 1.58 ± 0.21 Gg yr−1, in line with the bottom-up estimation of 1.50 Gg yr−1. Results indicate that CFC-11 emissions in the Pearl River Delta region have returned to levels before 2010, aligning with regional and global trends. Observations from XCG would compensate for the deficiency of CFC-11 measurements in southeastern China, paving the road for ODS studies in this region and beyond.

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“…Due to their ozone depleting potential (ODP), the production of CFCs for most uses is banned by the Montreal Protocol; accordingly, the atmospheric mixing ratios of the most abundant CFCs (e.g., CFC-11 and CFC-12) have declined in recent years, and there have been initial signs of ozone recovery [2,3,4,5,6]. However, the detection of unexpected sources of CFC emissions in recent years [7,8,9] has underscored the need to continually evaluate the consistency of reported values with atmospheric observations. Ensuring compliance with the Montreal Protocol requires that unexpected emissions of controlled substances be carefully considered -which in turn requires a thorough assessment of emissions from permitted sources.…”

Section: Introductionmentioning

confidence: 99%

Bayesian modeling of HFC production pipeline suggests growth in unreported CFC by-product and feedstock production

Bourguet,

Lickley

2024

Preprint

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Observationally-derived emissions of regulated ozone depleting substances (ODSs) must be scrutinized to maintain the progress made by the Montreal Protocol in protecting the stratospheric ozone layer. Recent observations of three chlorofluorocarbons (CFCs), CFC-113, CFC-114, and CFC-115, suggest that emissions of these compounds have been higher than expected given global reporting. These emissions have been associated with hydrofluorocarbon (HFC) production, which can require CFCs as feedstocks or generate CFCs as by-products, yet emissions from these pathways have not been rigorously quantified. Here, we develop a Bayesian framework to jointly infer emissions of CFC-113, CFC-114, CFC-115, and hydrochlorofluorocarbon HCFC-133a during HFC-134a and HFC-125 production. We estimate that feedstock usage in HFC-134a production accounted for 86% (75--92%) and 62% (46--74%) of CFC-113 and CFC-114 emissions, respectively, from 2015--2019, while by-product generation during HFC-125 production accounted for 81% (68--92%) of CFC-115 emissions. Our results suggest that unreported feedstock production in Article 5 countries may explain the unexpected atmospheric growth rates of CFC-113 and CFC-114, although uncertainties within the chemical manufacturing processes call for further investigation and industry transparency. Nonetheless, this work demonstrates the environmental benefits of tightened ODS feedstock regulations and underscores the importance of the HFC production phasedowns scheduled by the Kigali Amendment.

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Airborne Observations of CFCs Over Hebei Province, China in Spring 2016

Cited by 12 publications

References 77 publications

The return to 1980 stratospheric halogen levels: A moving target in ozone assessments from 2006 to 2022

The return to 1980 stratospheric halogen levels: A moving target in ozone assessments from 2006 to 2022

Observations and emission constraints of trichlorofluoromethane (CFC-11) in southeastern China: first-year results from a new AGAGE station

Bayesian modeling of HFC production pipeline suggests growth in unreported CFC by-product and feedstock production

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