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

==== 7.5.2.5 Assessment of ECS and TCR Based on the Instrumental Record ====

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Evidence from the instrumental temperature record, including estimates using global energy budget changes ( [[#7.5.2.1|Section 7.5.2.1]] ), climate emulators ( [[#7.5.2.2|Section 7.5.2.2]] ), variability in the TOA radiation budget ( [[#7.5.2.3|Section 7.5.2.3]] ), and the climate response to volcanic eruptions ( [[#7.5.2.4|Section 7.5.2.4]] ) produce median ECS estimates that range between 2.5°C and 3.5°C, but a best estimate value cannot be given owing to a strong dependence on assumptions about how radiative feedbacks will change in the future. However, there is ''robust evidence'' and ''high agreement'' across the lines of evidence that ECS is ''extremely likely'' greater than 1.6°C ( ''high confidence'' ). There is ''robust evidence'' and ''medium agreement'' across the lines of evidence that ECS is ''very likely'' greater than 1.8°C and ''likely'' greater than 2.2°C ( ''high confidence'' ). These ranges of ECS correspond to estimates based on historical global energy budget constraints ( [[#7.5.2.1|Section 7.5.2.1]] ) under the assumption of no feedback dependence on evolving SST patterns (i.e., α ’ = 0) and thus represent an underestimate of the true ECS ranges that can be inferred from this line of evidence ( ''high confidence'' ). Historical global energy budget changes do not provide constraints on the upper bound of ECS, while the studies assessed in ( [[#7.5.2.3|Section 7.5.2.3]] based on climate variability provide ''low confidence'' in its value owing to ''limited evidence'' .

Global energy budget constraints indicate a central estimate (median) TCR value of 1.9°C and that TCR is ''likely'' in the range 1.5 to 2.3 °C and ''very likely'' in the range 1.3 to 2.7 °C ( ''high confidence'' ). Studies that constrain TCR based on the instrumental temperature record used in conjunction with ESM simulations are summarized in ( [[#7.5.4.3|Section 7.5.4.3]] .

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