Aerosol forcing masks and delays the formation of the North-Atlantic warming hole by three decades

The North-Atlantic warming hole (NAWH) is referred to as a reduced warming, or even cooling, of the North-Atlantic during an anthropogenic-driven global warming. A NAWH is predicted by climate models during the 21st century and its pattern is already emerging in observations. Despite the known key role of the North-Atlantic surface temperatures in setting the Northern-Hemisphere climate, the mechanisms behind the NAWH are still not fully understood. Using state-of-the-art climate models, we show that anthropogenic aerosol forcing opposes the formation of the NAWH (by leading to a local warming) and delays its emergence by about 30 years. In agreement with previous studies, we also demonstrate that the relative warming of the North-Atlantic under aerosol forcing is due to changes in ocean heat fluxes, rather than air-sea fluxes. These results suggest that the predicted reduction in aerosol forcing during the 21st century may accelerate the formation of the NAWH