Extended Data Fig. 1: Surface dry-air mole fractions and growth rates for CFCs with increasing abundances.

Surface dry-air mole fractions and growth rates are shown for (a) CFC-13, (b) CFC-112a, (c) CFC-113a, (d) CFC-114a and (e) CFC-115 for the available direct atmospheric record (that is, excluding trends derived from firn air) from 1978 through 2020 (1999 through 2020 for CFC-112a). Circles show measured monthly mean mole fractions and lines are the model estimated mole fractions and growth rates, with the colours indicating the semi-hemispheric modelled estimate in which the measurement was made. Uncertainties (1 sd) are shown by the grey shading and are only shown for the global mean mole fractions and growth rates. Details on previously published records can be found in refs. ^8,9,17,18. CFC-13 abundances have increased continuously since 1978. The CFC-13 growth rate was rapid in the 1980s, slowed to 0.015 ppt yr⁻¹ in 2000, and subsequently increased over the next two decades. From 2010 to 2020, CFC-13 increased by 9% from 3.04 ppt to 3.31 ppt (3.44 ppt in 2020 using the NOAA record, only available since 2014; see Extended Data Fig. 2). CFC-112a has the lowest abundance of the five CFCs. Its abundance was declining 1999-2006, but rapidly grew from 2010 to 2020 by 19% from 0.066 ppt to 0.078 ppt. The CFC-113a abundance grew since 1978 at a rate less than 0.02 ppt yr⁻¹ until 2010, but from 2010 to 2020 it grew by 141% from 0.43 ppt to 1.02 ppt. CFC-114a growth rates were rapidly accelerating prior to 1990, then dropped to near zero between 1998–2003, after which they accelerated again. Between 2010 and 2020 CFC-114a increased by 9% from 1.03 ppt to 1.13 ppt. Similar to CFC-13 and CFC-114a, CFC-115 abundances also grew rapidly prior to the 1990s, but the timing is different. CFC-115 growth dropped to close to zero between 2005–2011, after which its growth rate again slowly increased. From 2010 to 2020, CFC-115 abundance grew by 4% from 8.38 ppt to 8.71 ppt (growing from 8.42 to 8.75 ppt from 2010 to 2020, or by 4%, using the NOAA record, Extended Data Fig. 2).