Abrupt shift of El Niño periodicity under CO2 mitigation

• 成果类型: Article
• 署名作者: Iwakiri, Tomoki; Kug, Jong-Seong; Jin, Fei-Fei; Zhao, Sen; An, Soon-Il; Kim, Geon-Il; Park, Dongkyu
• 署名单位: Seoul National University (SNU); Ochanomizu University; University of Hawaii System; University of Hawaii Manoa; University of Hawaii System; University of Hawaii Manoa; Yonsei University; University of Toronto
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9420
• DOI: 10.1073/pnas.2426048122
• 发表日期: 2025-06-24
• 关键词: nino southern-oscillation; ocean recharge paradigm; carbon-dioxide removal; interannual variability; equatorial pacific; enso; frequency; DYNAMICS; climate; locking

摘要

Removing CO2 from the atmosphere is emerging as a viable strategy to mitigate global warming, yet the responses of the climate system to CO2 reduction remain uncertain. One of the most uncertain aspects of El Ni & ntilde;o behavior is the change in periodicity in response to CO2 forcing [O. Alizadeh, Earth-Sci. Rev. 235, 104246 (2022)]. In this study, we show that climate models consistently project an abrupt shortening of El Ni & ntilde;o periodicity once CO2 reductions commence in ramp-up and ramp-down CO2 experiments. Besides the contribution of slow mean state changes, this phenomenon is shown to be driven by a southward shift of the Intertropical Convergence Zone (ITCZ) [J.- S. Kug, et al., Nat. Clim. Chang. 12, 47-53 (2022)] and the consequent narrowing of El Ni & ntilde;o's spatial pattern, which enhances the effectiveness of ocean heat recharge/ discharge processes, thereby shortening its periodicity. This suggests that the abrupt shift in El Ni & ntilde;o periodicity results from a cascading reaction involving ITCZ dynamics and El Ni & ntilde;o's spatial configuration. These findings highlight the critical role of the global energy balance in shaping El Ni & ntilde;o characteristics.