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. Plain Language Summary Anthropogenic aerosols are particles suspended in the atmosphere, which were released due to anthropogenic activity. These particles have a general cooling effect on the Earth due to their interactions with radiation and with clouds. Here we show that the surface temperature in the North Atlantic Ocean is predicted to increase due to aerosol forcing (despite the global cooling). This trend is the opposite of the surface temperature trend predicted due to increase in greenhouse gases (global warming with a warming “hole” in the North Atlantic, trend known as the North Atlantic warming hole—NAWH). Using state‐of‐the‐art climate models, we show that aerosol forcing delays the formation of the NAWH by about 30 years. This trend could have important climatic impacts due to the key role of the North Atlantic surface temperatures in setting the Northern Hemisphere's climate and due to the predicted reduction in aerosol forcing in the next few decades. Key Points Using CMIP6 and CESM‐LE simulations, we show that aerosol forcing generates a global cooling trend with a warming in the North Atlantic This trend opposes the North Atlantic warming hole trend due to greenhouse gases Aerosol forcing delays the formation of the North Atlantic warming hole by about 30 years