<p>Lingering global emissions of carbon tetrachloride (CCl<sub>4</sub>) are slowing ozone layer recovery. Estimates of global CCl<sub>4</sub> emissions based on observed atmospheric mole fractions and inverse modelling (top down) exceed the emissions derived from known sources (bottom up) by ~30–40%. Here we derived CCl<sub>4</sub> emissions from China for 2011–2021 using long-term atmospheric observations from a network of sites from across China and a top-down approach. Mean annual CCl<sub>4</sub> emissions in China during 2011–2021 were between approximately 16 Gg yr<sup>−1</sup> and 25 Gg yr<sup>−1</sup>, substantially larger than previous bottom-up inventories for China of less than 6 Gg yr<sup>−1</sup> since 2011. Expressed in terms of ozone depletion potential (ODP)-weighted emissions, CCl<sub>4</sub> annual emissions from China are comparable to global annual ‘unexpected’ trichlorofluoromethane (CFC-11) emissions during 2013–2018, or global total annual hydrochlorofluorocarbon emissions in 2020. The CCl<sub>4</sub> emissions from China accounted for approximately half of the reported global total during 2011–2020, with neither showing a significant decreasing trend during this period. Substantial CCl<sub>4</sub> emissions in China from allowed feedstock use, during the renewed production of CFC-11 between 2013 and 2018, and from by-production could close some of the emissions gap. However, ~4–15 Gg yr<sup>−1</sup> of CCl<sub>4</sub> emissions in China remain unexplained during 2011–2021, potentially accounting for more than half of the remaining global gap.</p>

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Persistent emissions of ozone-depleting carbon tetrachloride from China during 2011–2021

  • Minde An,
  • Bo Yao,
  • Luke M. Western,
  • Ronald G. Prinn,
  • Xingchen Zhao,
  • Jianxin Hu,
  • Jens Mühle,
  • Stefan Reimann,
  • Martin K. Vollmer,
  • Christina M. Harth,
  • Simon O’Doherty,
  • Ray F. Weiss,
  • Wenxue Chi,
  • Honghui Xu,
  • Yan Yu,
  • Anita L. Ganesan,
  • Matthew Rigby

摘要

Lingering global emissions of carbon tetrachloride (CCl4) are slowing ozone layer recovery. Estimates of global CCl4 emissions based on observed atmospheric mole fractions and inverse modelling (top down) exceed the emissions derived from known sources (bottom up) by ~30–40%. Here we derived CCl4 emissions from China for 2011–2021 using long-term atmospheric observations from a network of sites from across China and a top-down approach. Mean annual CCl4 emissions in China during 2011–2021 were between approximately 16 Gg yr−1 and 25 Gg yr−1, substantially larger than previous bottom-up inventories for China of less than 6 Gg yr−1 since 2011. Expressed in terms of ozone depletion potential (ODP)-weighted emissions, CCl4 annual emissions from China are comparable to global annual ‘unexpected’ trichlorofluoromethane (CFC-11) emissions during 2013–2018, or global total annual hydrochlorofluorocarbon emissions in 2020. The CCl4 emissions from China accounted for approximately half of the reported global total during 2011–2020, with neither showing a significant decreasing trend during this period. Substantial CCl4 emissions in China from allowed feedstock use, during the renewed production of CFC-11 between 2013 and 2018, and from by-production could close some of the emissions gap. However, ~4–15 Gg yr−1 of CCl4 emissions in China remain unexplained during 2011–2021, potentially accounting for more than half of the remaining global gap.