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

===== 2.2.3.2.3 Nitrous oxide (N <sub>2</sub> O) =====

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New records show that N <sub>2</sub> O concentration changes are associated with glacial-interglacial transitions ( [[#Schilt--2014|Schilt et al., 2014]] ). The most rapid change during the last glacial termination is a 30 ppb increase in a 200-year period, which is an order of magnitude smaller than the modern rate ( [[#2.2.3.3|Section 2.2.3.3]] ). During the LGM, N <sub>2</sub> O was 208.5 ± 7.7 ppb ( [[#Kageyama--2017|Kageyama et al., 2017]] ). Over the Holocene the lowest value was 257 ± 6.6 ppb during 6–8 ka, but millennial variation is not clearly detectable due to analytical uncertainty and insufficient ice core quality ( [[#Flückiger--2002|Flückiger et al., 2002]] ; [[#Schilt--2010|Schilt et al., 2010]] ). Recently acquired high-resolution records from Greenland and Antarctica for the last 2 kyr consistently show multi-centennial variations of about 5–10 ppb (Figure 2.4), although the magnitudes vary over time ( [[#Ryu--2020|Ryu et al., 2020]] ). Three high temporal resolution records exhibit a short-term minimum at about 600 CE of 261 ± 4 ppb ( [[#MacFarling%20Meure--2006|MacFarling Meure et al., 2006]] ; [[#Ryu--2020|Ryu et al., 2020]] ). It is ''very likely'' that industrial N <sub>2</sub> O increase started before 1900 CE ( [[#Machida--1995|Machida et al., 1995]] ; [[#Sowers--2001|Sowers, 2001]] ; [[#MacFarling%20Meure--2006|MacFarling Meure et al., 2006]] ; [[#Ryu--2020|Ryu et al., 2020]] ). Multiple ice cores show N <sub>2</sub> O concentrations of 270.1 ± 6.0 ppb in 1750 and 272.1 ± 5.7 ppb in 1850 ( [[#Machida--1995|Machida et al., 1995]] ; [[#Flückiger--1999|Flückiger et al., 1999]] ; [[#Sowers--2001|Sowers, 2001]] ; [[#Rubino--2019|Rubino et al., 2019]] ; [[#Ryu--2020|Ryu et al., 2020]] ).

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