Future Changes in Northern Hemisphere Summer Weather Persistence Linked to Projected Arctic Warming

Understanding the response of the large-scale atmospheric circulation to climatic change remains a key challenge. Specifically, changes in the equator-to-pole temperature difference have been suggested to affect the midlatitudes, potentially leading to more persistent extreme weather, but a scientific consensus has not been established so far. Here we quantify summer weather persistence by applying a tracking algorithm to lower tropospheric vorticity and temperature fields to analyze changes in their propagation speeds. We find significant links between slower propagating weather systems and a weaker equator-to-pole temperature difference in observations and models. By end of the century, the propagation of temperature anomalies over midlatitude land is projected to decrease by -3%, regionally strongest in southern North America (-45%) under a high emission scenario (CMIP5 RCP8.5). Even higher decreases are found (-10%, -58%) in models which project a decreasing equator-to-pole temperature difference. Our findings provide evidence that hot summer weather might become longer-lasting, bearing the risk of more persistent heat extremes.

Automated summary

The study reveals that when the equator-to-pole temperature difference is weaker, the propagation speed of summer weather systems slows down, leading to the possibility of hotter summer weather becoming more persistent, which could increase the risk of extreme heat waves.