Equatorial Pacific Warming Transition under CO2 Increase

Climate and oceans are complex and interdependent systems. Climate models indicate that an increase in CO2 can lead to an El Niño-like warming pattern in the Equatorial Pacific. However, recent observations show an increase in the zonal sea surface temperature (SST) gradient, which contradicts these projections. This raises doubts about the relevance of long-term forecasts for interpreting historical trends ¹.

Transition Mechanisms

A recent study identified a two-phase transition in the warming of the Equatorial Pacific under a scenario of abrupt CO2 increase. Initially, there is a strengthening of the SST gradient, followed by long-term weakening. To understand these mechanisms, researchers used a set of simulations with different representations of ocean dynamics. They discovered that the initial strengthening is influenced by changes in ocean circulation and atmospheric feedbacks from remote forcings in the Northern Hemisphere ^1,2.

The SST gradient in the Pacific is crucial for tropical circulation, precipitation, and global climate sensitivity. The study suggests that observed SST trends may reflect a rapid and forced response to CO2 increase. These findings highlight the importance of ocean dynamics and atmospheric feedbacks in understanding climate changes in the Equatorial Pacific ².