Issue AMOC weakening or collapse as a credible risk with monsoon and food impacts

Summary

The Atlantic Meridional Overturning Circulation is a density-driven current that carries warm water from the South Atlantic and tropics northward and helps keep northern Europe mild. More rain, shrinking sea ice and Greenland melt add freshwater to the North Atlantic and weaken the flow, and the report now treats a shutdown as a credible risk even under low to medium emission scenarios. A weaker circulation pushes the tropical rain belt south, weakening the Indian, southeast Asian and West African monsoons while strengthening and shifting the South American wet season. Half the world's population lives in monsoon regions and depends on the wet season for farming and fisheries, and model studies indicate an AMOC collapse could severely hurt water and food security in many countries. A weakened circulation could also warm the Southern Ocean and speed ice loss in parts of Antarctica. The report sees the AMOC as able to act both as a trigger and an amplifier for other tipping elements.