Editing IPCC:AR6/WGI/Chapter-7 (section)

==== 7.3.2.6 Stratospheric Water Vapour ====

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This section considers direct anthropogenic effects on stratospheric water vapour by oxidation of methane. Since AR5 the SARF from methane-induced stratospheric water vapour changes has been calculated in [[#Winterstein--2019|Winterstein et al., 2019]] , corresponding to 0.09 W m <sup>–2</sup> when scaling to 1850 to 2014 methane changes. This is marginally larger than the AR5 assessed value of 0.07 ± 0.05 W m <sup>–2</sup> ( [[#Myhre--2013b|Myhre et al., 2013b]] ). [[#Wang--2020|Wang and Huang (2020)]] quantified the adjustment terms to a stratospheric water vapour change equivalent to a forcing from a 2×CO <sub>2</sub> warming (which has a different vertical profile). They found that the ERF was less than 50% of the SARF due to high-cloud decrease and upper tropospheric warming. The assessed ERF is therefore 0.05 ± 0.05 W m <sup>–2</sup> with a lower limit reduced to zero and the central value and upper limit reduced to allow for adjustment terms. This still encompasses the two recent SARF studies. There is ''medium confidence'' in the SARF from agreement with the recent studies and AR5. There is ''low confidence'' in the adjustment terms.

Stratospheric water vapour may also change as an adjustment to species that warm or cool the upper troposphere–lower stratosphere region ( [[#Forster--2005|Forster and Joshi, 2005]] ; [[#Stuber--2005|Stuber et al., 2005]] ), in which case it should be included as part of the ERF for that compound. Changes in GSAT are also associated with changes in stratospheric water vapour as part of the water-vapour–climate feedback ( [[#7.4.2.2|Section 7.4.2.2]] ).

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