LAUSR

Significance Ship tracks have long been studied as a clear manifestation of broader anthropogenic aerosol effects, but typically only in specific regions or for relatively short periods of time. Now, with the help of a machine-learning algorithm we have detected all of the tracks across the world’s oceans over two decades—more than 1 million in total. This allows us to determine where tracks are more likely to form and the sensitivity of clouds to such perturbations. Crucially, we see a sharp reduction in tracks due to the more stringent ship emission regulations since 2020. This constitutes clear evidence of a global cloud response to environmental regulations despite no such change being observed in other cloud properties.