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

===== 7.4.4.2.3 Overall assessment of tropical Pacific sea surface temperature gradients under CO 2 forcing =====

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The paleoclimate proxy record and ESM simulations of the MPWP, process understanding, and ESM projections of climate response to CO <sub>2</sub> forcing provide ''medium evidence'' and a ''medium agreement'' and thus ''medium confidence'' that equilibrium warming in response to elevated CO <sub>2</sub> will be characterized by a weakening of the east–west tropical Pacific SST gradient.

Overall the observed pattern of warming over the instrumental period, with a warming minimum in the eastern tropical Pacific Ocean (Figure 7.14a), stands in contrast to the equilibrium warming pattern either inferred from the MPWP proxy record or simulated by ESMs under CO <sub>2</sub> forcing. There is ''medium confidence'' that the observed strengthening of the east–west SST gradient is temporary and will transition to a weakening of the SST gradient on centennial time scales. However, there is only ''low confidence'' that this transition will emerge this century owing to a low degree of agreement across studies about the factors driving the observed strengthening of the east–west SST gradient and how those factors will evolve in the future. These trends in tropical Pacific SST gradients reflect changes in the climatology, rather than changes in ENSO amplitude or variability, which are assessed in ( [[IPCC:Wg1:Chapter:Chapter-4|Chapter 4]] [[IPCC:Wg1:Chapter:Chapter-4#4.3.3|Section 4.3.3]] ).

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