Human influence on the recent weakening of storm tracks in boreal summer

Abstract

Anthropogenic warming can alter large-scale circulation patterns in the atmosphere, which could have serious consequences for regional climate impacts and extreme weather. Observed thermodynamic changes in boreal extratropics have been attributed to human emissions with high confidence, but most circulation changes have not. In particular, not only that in the previous suite of climate models most models do not capture the recent boreal summer storm tracks weakening, but also a quantification of the role of human emissions in the recent storm tracks weakening has not been conducted to date. Here we use the latest suite of climate models, which are found to adequately capture the recent storm tracks weakening, and show that this weakening is attributable to anthropogenic emissions. Human emissions have resulted in more-rapid warming of the high latitudes, and the associated reduction in poleward temperature gradient has weakened the storms. The physical consistency between models and reanalyses increases our confidence in the projected weakening, which presents regional risks including hot-dry extremes in summer.