SPARC Report on the Mystery of Carbon Tetrachloride

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CCl4 is a major ODS, accounting for about 12% of the globally averaged inorganic chlorine and bromine in the stratosphere, compared to 14% for CFC-12 in 2012. In spite of the MP controls, there are large ongoing emissions of CCl4 into the atmosphere. Estimates of emissions from various techniques ought to yield similar numbers. However, the recent WMO-UNEP Scientific Assessment of Ozone Depletion estimated a 2007-2012 CCl4 bottom-up emission of 1-4 Gg per year (1-4 kilotonnes per year), based on country-by-country reports to UNEP, and a global top-down emissions estimate of 57 Gg per year, based on atmospheric measurements. This 54 Gg per year difference has not been explained.

SPARC Report on the Mystery of Carbon Tetrachloride, Q. Liang, P.A. Newman, S. Reimann (Eds.), SPARC Report No. 7, WCRP-13/2016. doi: