Editing IPCC:AR6/WGI/Chapter-2 (section)

==== 2.2.4.2 Hydrochlorofluorocarbons (HCFCs) ====

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The atmospheric abundances of the major HCFCs (HCFC-22, HCFC-141b, HCFC-142b), primarily used in refrigeration and foam blowing, are increasing, but rates of increase have slowed in recent years (Figure 2.6). Global mean mixing ratios (Table 2.2) showed good concordance at the time of AR5 for the period 2005–2011. For the period 2011–2019, the UCI network detected larger increases in HCFC-22, HCFC-141b, and HCFC-142b compared to the NOAA and AGAGE networks. Reasons for the discrepancy are presently unverified, but could be related to differences in sampling locations in the networks ( [[#Simpson--2012|Simpson et al., 2012]] ). Emissions of HCFC-22, derived from atmospheric data, have remained relatively stable since 2012, while those of HCFC-141b and HCFC-142b have declined ( [[#Engel--2018|Engel et al., 2018]] ). Minor HCFCs, HCFC-133a and HCFC-31, have been detected in the atmosphere (currently less than 1 ppt) and may be unintentional by-products of HFC production ( [[#Engel--2018|Engel et al., 2018]] ).

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