Chloroform contributes to the depletion of the stratospheric ozone layer. However, due to its short lifetime and predominantly natural sources, it is not included in the Montreal Protocol that regulates the production and uses of ozone-depleting substances. Atmospheric chloroform mole fractions were relatively stable or slowly decreased during 1990–2010. Here we show that global chloroform mole fractions increased after 2010, based on in situ chloroform measurements at seven stations around the world. We estimate that the global chloroform emissions grew at the rate of 3.5% yr−1 between 2010 and 2015 based on atmospheric model simulations. We used two regional inverse modelling approaches, combined with observations from East Asia, to show that emissions from eastern China grew by 49 (41–59) Gg between 2010 and 2015, a change that could explain the entire increase in global emissions. We suggest that if chloroform emissions continuously grow at the current rate, the recovery of the stratospheric ozone layer above Antarctica could be delayed by several years.
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The data that support the findings of this study are available from the corresponding author upon request. CHCl3 measurement data for East Asia can be accessed by contacting data leads: S.P. (firstname.lastname@example.org) for GSN and T.S. (email@example.com) for HAT. CHCl3 measurement data for the five non-Asian AGAGE stations (CGO, SMO, RPB, THD and MHD) used in this study are available at http://agage.mit.edu/data/agage-data/.
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X.F., R.G.P. and A.G. are supported by the National Aeronautics and Space Administration (NASA) grant nos NAG5-12669, NNX07AE89G, NNX11AF17G and NNX16AC98G to MIT. T.S., Y.Y. and the Hateruma station are supported fully by the Ministry of Environment of Japan and NIES. S.P., S.L. and the Gosan AGAGE station are supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (no. NRF-2016R1A2B2010663). R.T. was funded under Natural Environment Research Council (NERC) grant no. NE/M014851/1. A.L.G. was funded under a NERC Independent Research Fellowship (NE/L010992/1). M.R. was funded under a NERC Advanced Fellowship (NE/I021365/1). P.J.F., P.B.K. and the CGO AGAGE station are supported by CSIRO, the Bureau of Meteorology, Refrigerant Reclaim Australia and NASA grants to MIT. The operations of the AGAGE stations were/are supported by the NASA (grant nos NAG5-12669, NNX07AE89G, NNX11AF17G and NNX16AC98G to MIT; grant nos NAG5-4023, NNX07AE87G, NNX07AF09G, NNX11AF15G, NNX11AF16G, NNX16AC96G and NNX16A97G to SIO). In addition to the NASA funding, MHD was/is supported by the Department for Business, Energy & Industrial Strategy (BEIS, UK, formerly the Department of Energy and Climate Change (DECC)) contract nos GA01081, GA0201, 1028/06/2015 and 1537/06/2018 to the University of Bristol and the UK Meteorological Office. The RPB station was/is also additionally supported by the National Oceanic and Atmospheric Administration (NOAA), contract nos RA-133-R09-CN-0062 and RA-133-R15-CN-0008 to the University of Bristol; the NOAA supports the operations of the SMO station.