Surface weather conditions are closely governed by the large-scale circulation of the Earth’s atmosphere. Recent increases in the occurrence of some extreme weather phenomena have led to multiple mechanistic hypotheses linking changes in atmospheric circulation to increasing probability of extreme events. However, observed evidence of long-term change in atmospheric circulation remains inconclusive.

Poor air quality causes an estimated 2.6–4.4 million premature deaths per year. Hazardous conditions form when meteorological components allow the accumulation of pollutants in the near-surface atmosphere. Global-warming-driven changes to atmospheric circulation and the hydrological cycle are expected to alter the meteorological components that control pollutant build-up and dispersal, but the magnitude, direction, geographic footprint and public health impact of this alteration remain unclear.