Editing IPCC:AR6/WGI/Chapter-1 (section)

===== ''1.4.3.1.2 Climate respo'' ''nse uncertainty'' =====

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Under any particular scenario ( [[#1.6.1|Section 1.6.1]] ), there is uncertainty in how the climate will respond to the specified emissions or radiative forcing combinations. A range of climate models is often used to estimate the range of uncertainty in our understanding of the key physical processes and to define the ‘model response uncertainty’ (Sections [[#1.5.4|1.5.4]] and [[IPCC:Wg1:Chapter:Chapter-4#4.2.5|4.2.5]] ). However, this range does not necessarily represent the full ‘climate response uncertainty ''’'' in how the climate may respond to a particular radiative forcing or emissions scenario. This is because, for example, the climate models used in CMIP experiments have structural uncertainties not explored in a typical multi-model exercise (e.g., [[#Murphy--2004|Murphy et al., 2004]] ) and are not entirely independent of each other ( [[#1.5.4.8|Section 1.5.4.8]] ; [[#Masson--2011|Masson and Knutti, 2011]] ; [[#Abramowitz--2019|Abramowitz et al., 2019]] ); there are small spatial-scale features which cannot be resolved; and long time-scale processes or tipping points are not fully represented. [[#1.4.4|Section 1.4.4]] discusses how some of these issues can still be considered in a risk assessment context. For some metrics, such as equilibrium climate sensitivity (ECS), the CMIP6 model range is found to be broader than the ''very likely'' range assessed by combining multiple lines of evidence (Sections 4.3.4 and 7.5.6).

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