Editing IPCC:AR6/WGI/Chapter-4 (section)

==== 4.5.3.4 Tropical Atlantic Modes ====

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The AR5 assessed that there is ''low confidence'' in projected changes of the Tropical Atlantic Variability (TAV) because of the general failure of climate models to simulate main aspects of this variability such as the northward displaced ITCZ. The models that best represent the Atlantic meridional mode (AMM) show a weakening for future climate conditions. However, model biases in representation of Altantic Niños strongly limit an assessment of future changes.

Long-term changes in TAVs and associated teleconnections are expected as a result of global warming, but large uncertainties exist due to the models’ systematic underestimation of the connection between PDV and Indo-Pacific SST variations ( [[#Lübbecke--2018|Lübbecke et al., 2018]] ; [[#Cai--2019|Cai et al., 2019]] ). Observational analyses show large discrepancies in SST and trade wind strength ( [[#Servain--2014|Servain et al., 2014]] ; [[#Mohino--2015|Mohino and Losada, 2015]] ). Single-model sensitivity experiments show that Atlantic Niño characteristics at the end of 21st century remain consistent with those of the 20th century, though changes in the climatological SSTs can lead to changes in the associated teleconnections ( [[#Mohino--2015|Mohino and Losada, 2015]] ).

The weakening of the AMOC expected from global warming (see [[#4.3.2.3|Section 4.3.2.3]] ) has been suggested to have an influence on the mean background state of tropical-Atlantic surface conditions, thereby enhancing equatorial Atlantic variability and resulting in a stronger tropical Atlantic–ENSO teleconnection (see [[IPCC:Wg1:Chapter:Chapter-3#3.7.5|Section 3.7.5]] for a detailed discussion; [[#Svendsen--2014|Svendsen et al., 2014]] ). A recent multi-model study, based on CMIP5, concluded that the TAV-Pacific teleconnection will weaken under global warming due to the increased thermal stability of the atmosphere (F. [[#Jia--2019|]] [[#Jia--2019|Jia et al., 2019]] ). However, there is still a clear lack of model studies, and hence no robust evidence on the long-term evolution of TAV and associated teleconnections.

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