Hysteresis of European summer precipitation under a symmetric CO 2 ramp-up and ramp-down pathway

• Published in: Environmental research letters 2024-07, Vol.19 (7), p.74030
• Main Authors: Im, Nari, Kim, Daehyun, An, Soon-Il, Paik, Seungmok, Kim, Soong-Ki, Shin, Jongsoo, Min, Seung-Ki, Kug, Jong-Seong, Oh, Hyoeun
• Format: Article
• Language: English
• ISSN: 1748-9326; 1748-9326
• DOI: 10.1088/1748-9326/ad52ad

This study investigates the mechanism of the hysteresis of European summer mean precipitation in a CO 2 removal (CDR) simulation. The European summer mean precipitation exhibits robust hysteresis in response to the CO 2 forcing; after decreasing substantially (∼40%) during the ramp-up period, it shows delayed recovery during the ramp-down period. We found that the precipitation hysteresis over Europe is tied to the hysteresis in the Atlantic Meridional Overturning Circulation (AMOC). During the ramp-down period, an anomalous high surface pressure circulation prevails over Europe. The anomalous high pressure system is a baroclinic response of the atmosphere to strong North Atlantic cooling associated with a weakened AMOC. This anomalous circulation suppresses summertime convective activity over the entire Europe by decreasing near-surface moist enthalpy in Central and Northern Europe while increasing lower free-tropospheric temperature in Southern Europe. Our findings underscore the need to understand complex interactions in the Earth system for reliable future projections of regional precipitation change under CDR scenarios.