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

• Published in: Geophysical research letters Vol. 48; no. 4
• Main Authors: Kornhuber, Kai, Tamarin‐Brodsky, Talia
• Format: Journal Article
• Language: English
• Published: 28.02.2021
• Subjects: arctic amplification; climatic change; extreme weather; large scale dynamics
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL091603

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. Key Points Summer heat anomalies in the northern hemisphere will become more persistent in the midlatitudes, especially in southern North America where summer weather patterns and associated temperature anomalies are projected to slow‐down by more than 45% by the end of the century There are robust relationships between Arctic warming at near surface levels and midlatitude weather persistence in observations and models Models disagree on the sign of equator‐to‐pole temperature gradient change during summer, but those models that agree with observations, a warming Arctic, show a stronger trend toward increased persistence over midlatitude land area (−10%)