Surface Temperature Reversibility and the Roles of Clouds on the Decadal Time Scale.
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| Title: | Surface Temperature Reversibility and the Roles of Clouds on the Decadal Time Scale. |
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| Authors: | Ge, Qi1 (AUTHOR), Wang, Yuan1 (AUTHOR) yzwang@stanford.edu, Jiang, Jonathan H.2 (AUTHOR) |
| Source: | Journal of Climate. Apr2026, Vol. 39 Issue 8, p1955-1970. 16p. |
| Subjects: | Climate feedbacks, Ocean circulation, Radiation, Surface temperature, Polar climate, Atmospheric models, Antarctic ice |
| Geographic Terms: | Southern Hemisphere, Atlantic Ocean, Antarctica, Antarctic Ocean |
| Abstract: | Climate mitigation strategies have been proposed to halt and potentially reverse global warming trends by the mid-twenty-first century. Previous studies have shown different aspects of climate irreversibility at regional or global scales, but the roles of clouds and atmospheric radiation remain elusive. Using the fully coupled NCAR Community Earth System Model, version 2 (CESM2), we examine climate reversibility in a scenario where the atmospheric carbon dioxide (CO2) concentration gradually increases starting in 2015 (∼400 ppm) until 2075 (∼800 ppm) and then decreases back to the 2015 level. We find that the lowest reversibility of surface temperature occurs in the Southern Hemisphere mid–high latitudes. In addition to the slow ocean response, profound cloud–radiation feedbacks are identified in this study, which contribute to regional temperature irreversibility. Cloud properties and radiative effects show the lowest reversibility over 30°–45° and 60°–75°S. The strong inertia of the Southern Ocean circulations and the Atlantic meridional overturning circulation (AMOC) jointly induce hemispheric surface temperature asymmetry on a 60-yr time scale, leading to a southward shift of the Hadley cell with a narrowed subsidence branch and a persistent moisture divergence over 30°–45°S during the removal of CO2. The resultant humidity reduction decreases low-level cloud fraction and liquid water path, contributing to anomalous shortwave radiation that suppresses local temperature recovery. Moreover, subpolar clouds in the Southern Hemisphere are closely connected with Antarctic sea ice which exhibits substantial irreversibility following the Southern Ocean circulation responses. Our findings demonstrate that coupled ocean–atmosphere processes involving cloud and radiation feedbacks collectively determine climate reversibility and shape regional climate change patterns. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Climate mitigation strategies have been proposed to halt and potentially reverse global warming trends by the mid-twenty-first century. Previous studies have shown different aspects of climate irreversibility at regional or global scales, but the roles of clouds and atmospheric radiation remain elusive. Using the fully coupled NCAR Community Earth System Model, version 2 (CESM2), we examine climate reversibility in a scenario where the atmospheric carbon dioxide (CO2) concentration gradually increases starting in 2015 (∼400 ppm) until 2075 (∼800 ppm) and then decreases back to the 2015 level. We find that the lowest reversibility of surface temperature occurs in the Southern Hemisphere mid–high latitudes. In addition to the slow ocean response, profound cloud–radiation feedbacks are identified in this study, which contribute to regional temperature irreversibility. Cloud properties and radiative effects show the lowest reversibility over 30°–45° and 60°–75°S. The strong inertia of the Southern Ocean circulations and the Atlantic meridional overturning circulation (AMOC) jointly induce hemispheric surface temperature asymmetry on a 60-yr time scale, leading to a southward shift of the Hadley cell with a narrowed subsidence branch and a persistent moisture divergence over 30°–45°S during the removal of CO2. The resultant humidity reduction decreases low-level cloud fraction and liquid water path, contributing to anomalous shortwave radiation that suppresses local temperature recovery. Moreover, subpolar clouds in the Southern Hemisphere are closely connected with Antarctic sea ice which exhibits substantial irreversibility following the Southern Ocean circulation responses. Our findings demonstrate that coupled ocean–atmosphere processes involving cloud and radiation feedbacks collectively determine climate reversibility and shape regional climate change patterns. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 08948755 |
| DOI: | 10.1175/JCLI-D-25-0488.1 |
