Global warming makes weather in boreal summer more persistent

Abstract

Abstract. Extreme summer weather often has devastating impacts on society when it lasts for many days. Stalling cyclones can lead to flooding and persistent hot-dry conditions can lead to health impacts and harvest losses. Global warming weakens the hemispheric-wide circulation in boreal summer, which has been shown in both observations and models using multiple circulation metrics. Until now, it is still largely unclear what this weakening implies for regional weather conditions, including their persistence. Using an advanced persistence metric, we show that summer weather has become more-persistent over 1979–2019. State-of-the-art climate models reproduce this upward trend in persistence indicating that it can be attributed to greenhouse gas forcing. Our persistence metric accounts for the full state of the atmosphere at any given moment and is strongly rooted in dynamical systems theory. Thereby it is able to detect dynamical changes previously unseen in more widely used clustering analyses that sharply reduce the amount of information used. We show that under future high-emission scenarios, summer weather will become increasingly more-persistent due to a weakening of the circulation. Most of this increase in persistence, and the associated societal risks, is avoided under an emission scenario compatible with the Paris agreement.

Increased spatial extent and likelihood of compound long-duration dry and hot events in China, 1961–2014

“…Yang et al: Increased spatial extent and likelihood of compound long-duration dry and hot events in China ment of the characteristics and possible changes in such longduration extreme events. Previous studies indicate that summer weather has become more persistent over recent decades due to anomalous atmospheric circulation patterns and global warming (Coumou and De Luca, 2020;Pfleiderer et al, 2019). More long-duration extremes have been observed recently (Breinl et al, 2020;Kornhuber et al, 2019;Zscheischler and Fischer, 2020).…”

On the persistence of near‐surface temperature dynamics in a warming world

“…While the first two have received significant attention, [13][14][15] studies about the effects of changes in persistence on the probabilities of occurrence of extremes are much scarcer. [16][17][18] However, recent events with seemingly larger than usual duration, magnitude, and frequency 19 have invigorated research efforts for better understanding of the influence and nature of trends, changes in variability, and persistence over extremes. 15,18,[20][21][22][23][24][25] However, to obtain an adequate estimation of persistence, it is crucial to properly account for trends and noise.…”

“…Such modifications can be produced by changes in the mean (i.e., existence of trends) and/or variability, as well as in the persistence of some variables of the climate system, or a combination of them. While the first two have received significant attention, 13–15 studies about the effects of changes in persistence on the probabilities of occurrence of extremes are much scarcer 16–18 . However, recent events with seemingly larger than usual duration, magnitude, and frequency 19 have invigorated research efforts for better understanding of the influence and nature of trends, changes in variability, and persistence over extremes 15,18,20–25 .…”

“…used monthly data, with the first two focusing on sea surface temperature. Di Cecco and Gouhier 37 and Coumou and De Luca 16 used daily data, with the former indicating that the autocorrelation increased over time, while the latter showed that the summer weather has become more persistent over 1979–2019. Li and Thompson 31 also used daily data produced by various physical climate models and documented a widespread increase of autocorrelations from the period 1970–1999 to the period 2070–2099.…”

Increased spatial extent and likelihood of compound long-duration dry and hot events in China, 1961–2014

“…Previous studies indicate that summer weather has become more persistent over recent decades due to anomalous atmospheric circulation patterns and global warming (Coumou and Luca, 2020;Pfleiderer et al, 2019). More long-duration extremes have been observed recently (Breinl et al, 2020;Kornhuber et al, 2019;Zscheischler and Fischer, 2020).…”