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

==== 7.3.2.3 Nitrous oxide (N <sub>2</sub> O) ====

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The tropospheric adjustments to nitrous oxide (N <sub>2</sub> O) have been calculated from 5 ESMs as 7% ± 13% of the SARF ( [[#Hodnebrog--2020b|Hodnebrog et al., 2020b]] ). This value is therefore taken as the assessed adjustment, but with ''low confidence'' . The radiative modelling uncertainty is ±10% ( [[#Etminan--2016|Etminan et al., 2016]] ), giving an overall uncertainty of ±16%. Nitrous oxide concentrations have increased from 270 ppb in 1750 to 332 ppb in 2019 [[IPCC:Wg1:Chapter:Chapter-2#2.2.3.3|Section 2.2.3.3]] ). The historical ERF estimate from N <sub>2</sub> O is revised upwards from 0.17 ± 0.06 W m <sup>–2</sup> (1750–2011) in AR5 to 0.21 ± 0.03 W m <sup>–2</sup> (1750–2019) in this assessment, of which 0.02 W m <sup>–2</sup> is due to the 7 ppb increase in concentrations, and 0.02 W m <sup>–2</sup> to the tropospheric adjustment. As the adjustments are assessed to be small there remains ''high confidence'' in the overall assessment.

Increased nitrous oxide leads to ozone depletion in the upper stratosphere which will make a positive contribution to the direct ERF here (Section 6.4.2 and Figure 6.12) when considering emissions-based estimates of ERF.

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