The Tropical Atlantic Gradient in Global Climate Models

The Tropical Atlantic Gradient (TAG), the sea surface temperature difference between the Tropical North Atlantic and Tropical South Atlantic, strongly affects the latitude of the Atlantic Intertropical Convergence Zone, and precipitation in the Caribbean, Northeast Brazil, and West Africa. The TAG appears to have decreased in the second half of the 20th century until increasing in the last two decades, with aerosol forcing and the Atlantic meridional overturning circulation considered the most likely explaining mechanisms. Global climate models (GCMs) do not predict a consistent response in the TAG under climate change scenarios. We investigate the TAG in several GCMs from the World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project (CMIP) to understand the mechanisms that influence its twentieth-century behavior. We also examine these mechanisms in future climate simulations to better understand why different models project different TAG changes.