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

==== 7.5.2.4 Estimates of ECS Based on the Climate Response to Volcanic Eruptions ====

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A number of studies consider the observed climate response to volcanic eruptions over the 20th century ( [[IPCC:Wg1:Chapter:Chapter-3#3.3.1|Section 3.3.1]] and Cross-Chapter Box 4.1; [[#Knutti--2017|Knutti et al., 2017]] ). However, the direct constraint on ECS is weak, particularly at the high end, because the temperature response to short-term forcing depends only weakly on radiative feedbacks and because it can take decades of a sustained forcing before the magnitude of temperature changes reflects differences in ECS across models ( [[#Geoffroy--2013b|Geoffroy et al., 2013b]] ; [[#Merlis--2014|Merlis et al., 2014]] ). It is also a challenge to separate the response to volcanic eruptions from internal climate variability in the years that follow them ( [[#Wigley--2005|Wigley et al., 2005]] ). Based on ESM simulations, radiative feedbacks governing the global surface temperature response to volcanic eruptions can be substantially different than those governing long-term global warming ( [[#Merlis--2014|Merlis et al., 2014]] ; [[#Marvel--2016|Marvel et al., 2016]] ; [[#Ceppi--2019|Ceppi and Gregory, 2019]] ). Estimates based on the response to volcanic eruptions agree with other lines of evidence ( [[#Knutti--2017|Knutti et al., 2017]] ), but they do not constitute a direct estimate of ECS ( ''high confidence'' ). The ‘emergent constraints’ on ECS based on climate variability, including volcanic eruptions, are summarized in ( [[#7.5.4.1|Section 7.5.4.1]] .

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