Climate change is expected to increase atmospheric stagnation events through changes in circulation and the hydrological cycle, reports a paper published online this week in Nature Climate Change. Atmospheric stagnation, in which an air mass remains over an area for an extended period, can have serious health implications, such as cardiovascular disease and respiratory problems, due to increased pollution exposure.

Daniel Horton and colleagues investigate future stagnation events by applying an air stagnation index to a collection of global climate models. Using a high-emissions scenario, the authors examine changes in the frequency and duration of events. They project an increase in stagnation occurring over 55% of the current global population, with increases of up to 40 additional days a year over the majority of the tropics and subtropics.

India, Mexico and the western US are most at risk of health impacts due to an increase in stagnation events occurring in areas with large populations. These results suggest that climate change means there will need to be better pollution management to ensure air-quality standards are met.