Chlorofluorocarbon (CFC) banks from uses such as air conditioners or foams can be emitted after global production stops. Recent reports of unexpected emissions of CFC-11 raise the need to better ...quantify releases from these banks, and associated impacts on ozone depletion and climate change. Here we develop a Bayesian probabilistic model for CFC-11, 12, and 113 banks and their emissions, incorporating the broadest range of constraints to date. We find that bank sizes of CFC-11 and CFC-12 are larger than recent international scientific assessments suggested, and can account for much of current estimated CFC-11 and 12 emissions (with the exception of increased CFC-11 emissions after 2012). Left unrecovered, these CFC banks could delay Antarctic ozone hole recovery by about six years and contribute 9 billion metric tonnes of equivalent CO
emission. Derived CFC-113 emissions are subject to uncertainty, but are much larger than expected, raising questions about its sources.
Global emissions of the ozone-depleting gas HCFC-141b (1,1-dichloro-1-fluoroethane, CH3CCl2F) derived from measurements of atmospheric mole fractions increased between 2017 and 2021 despite a fall in ...reported production and consumption of HCFC-141b for dispersive uses.
HCFC-141b is a controlled substance under the Montreal Protocol, and its phase-out is currently underway, after a peak in reported consumption and production in developing (Article 5) countries in 2013.
If reported production and consumption are correct, our study suggests that the 2017–2021 rise is due to an increase in emissions from the bank when appliances containing HCFC-141b reach the end of their life, or from production of HCFC-141b not reported for dispersive uses.
Regional emissions have been estimated between 2017–2020 for all regions where measurements have sufficient sensitivity to emissions.
This includes the regions of northwestern Europe, east Asia, the United States and Australia, where emissions decreased by a total of 2.3 ± 4.6 Gg yr−1, compared to a mean global increase of 3.0 ± 1.2 Gg yr−1 over the same period.
Collectively these regions only account for around 30 % of global emissions in 2020.
We are not able to pinpoint the source regions or specific activities responsible for the recent global emission rise.
Carbon tetrachloride (CCl4) is a major anthropogenic ozone‐depleting substance and greenhouse gas and has been regulated under the Montreal Protocol. However, the near‐zero 2007–2012 emissions ...estimate based on the UNEP reported production and feedstock usage cannot be reconciled with the observed slow decline of atmospheric concentrations and the inter‐hemispheric gradient (IHG) for CCl4. Our 3‐D model simulations suggest that the observed IHG (1.5 ± 0.2 ppt for 2000–2012) is primarily caused by ongoing current emissions, while ocean and soil losses and stratosphere‐troposphere exchange together contribute a small negative gradient (~0 – −0.3 ppt). Using the observed CCl4 global trend and IHG, we deduce that the mean global emissions for the 2000–2012 period are 393445 Gg/yr (~30% of the peak 1980s emissions) and a corresponding total lifetime of 353732 years.
Key Points
Near‐zero CCl4 bottom‐up emissions cannot be reconciled with observations
The observed inter‐hemispheric gradient can be used to quantify CCl4 emissions
The likely mean CCl4 global emissions are 39 Gg/yr and lifetime is 35 years
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Emissions of the potent greenhouse gas perfluorocyclobutane
(c-C4F8, PFC-318, octafluorocyclobutane) into the global atmosphere
inferred from atmospheric measurements have been increasing sharply ...since
the early 2000s. We find that these inferred emissions are highly correlated
with the production of hydrochlorofluorocarbon-22 (HCFC-22, CHClF2) for
feedstock (FS) uses, because almost all HCFC-22 FS is pyrolyzed to produce
(poly)tetrafluoroethylene ((P)TFE) and hexafluoropropylene (HFP), a process
in which c-C4F8 is a known by-product, causing a significant
fraction of global c-C4F8 emissions. We find a global emission
factor of ∼0.003 kg c-C4F8 per kilogram of HCFC-22 FS
pyrolyzed. Mitigation of these c-C4F8 emissions, e.g., through
process optimization, abatement, or different manufacturing processes, such
as refined methods of electrochemical fluorination and waste recycling,
could reduce the climate impact of this industry. While it has been shown
that c-C4F8 emissions from developing countries dominate global
emissions, more atmospheric measurements and/or detailed process statistics
are needed to quantify c-C4F8 emissions at country to facility
levels.
Emissions of the potent greenhouse gas perfluorocyclobutane (c-C.sub.4 F.sub.8, PFC-318, octafluorocyclobutane) into the global atmosphere inferred from atmospheric measurements have been increasing ...sharply since the early 2000s. We find that these inferred emissions are highly correlated with the production of hydrochlorofluorocarbon-22 (HCFC-22, CHClF.sub.2) for feedstock (FS) uses, because almost all HCFC-22 FS is pyrolyzed to produce (poly)tetrafluoroethylene ((P)TFE) and hexafluoropropylene (HFP), a process in which c-C.sub.4 F.sub.8 is a known by-product, causing a significant fraction of global c-C.sub.4 F.sub.8 emissions. We find a global emission factor of â¼0.003 kg c-C.sub.4 F.sub.8 per kilogram of HCFC-22 FS pyrolyzed. Mitigation of these c-C.sub.4 F.sub.8 emissions, e.g., through process optimization, abatement, or different manufacturing processes, such as refined methods of electrochemical fluorination and waste recycling, could reduce the climate impact of this industry. While it has been shown that c-C.sub.4 F.sub.8 emissions from developing countries dominate global emissions, more atmospheric measurements and/or detailed process statistics are needed to quantify c-C.sub.4 F.sub.8 emissions at country to facility levels.
Carbon tetrachloride (CCl4) is a major anthropogenic ozone-depleting substance and greenhouse gas and has been regulated under the Montreal Protocol. However, atmospheric observations show a very ...slow decline in CCl4 concentrations, inconsistent with the nearly zero emissions estimate based on the UNEP reported production and feedstock usage in recent years. It is now apparent that there are either unidentified industrial leakages, an unknown production source of CCl4, or large legacy emissions from CCl4 contaminated sites. In this paper we use a global chemistry climate model to assess the budget mystery of atmospheric CCl4. We explore various factors that affect the global trend and the gradient between the Northern and Southern hemispheres or interhemispheric gradient (IHG): emissions, emission hemispheric partitioning, and lifetime variations. We find a present-day emission of 30-50 Gg per yr and a total lifetime 25 - 36 years are necessary to reconcile both the observed CCl4 global trend and IHG.
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