Air quality improvements are projected to weaken the Atlantic meridional overturning circulation through radiative forcing effects

Abstract

Observations indicate the Atlantic Meridional Overturning Circulation-a fundamental component of the ocean’s global conveyor belt-is weakening. Although causes remain uncertain, such weakening is consistent with increasing greenhouse gases. Recent studies also suggest that anthropogenic emissions associated with air pollution can impact the Atlantic Meridional Overturning Circulation. Here, we use four state-of-the-art chemistry-climate models to quantify how efforts to improve future air quality, via near-term climate forcer mitigation, will impact the Atlantic Meridional Overturning Circulation. Future reductions in aerosols, ozone and precursor gases alone induces end-of-century weakening of the Atlantic Meridional Overturning Circulation by up to 10%. However, when methane reductions are also included, this weakening is offset. The responses are best explained by changes in the North Atlantic radiative forcing. Thus, efforts to improve air quality must also target methane and other greenhouse gases including carbon dioxide to avoid weakening of the world’s major ocean circulation system.