Southern Ocean Control of 2°C Global Warming in Climate Models

• Published in: Earth's Future
• Main Authors: So‐Jung Shin, Sang‐Wook Yeh, Soon‐Il An, Noel Keenlyside, Shang‐Ping Xie, Jae‐Heung Park
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: southern ocean condition; low level cloud amount feedback; Paris agreement; Antarctic sea ice; Environmental sciences; GE1-350; Ecology; QH540-549.5; Antarctic; Southern Ocean; Antarc*; Sea ice
• Online Access: https://doi.org/10.1029/2022EF003212; https://doaj.org/article/f128ed3ff5344d1d911aea7400f06126

Abstract Global warming will soon reach the Paris Agreement targets of 1.5°C/2°C temperature increase above pre‐industrial levels. Under a business‐as‐usual scenario, the time to reach these targets varies widely among climate models. Using Coupled Model Intercomparison Project Phase 5 and 6, we show that a 2°C global warming is determined by Southern Ocean (SO) state closely tied with a low‐level cloud (LLC) amount feedback strength during reference (1861–1900) period; climate models with cold SO tend to accompany more low‐level cloudiness and Antarctic sea ice concentration due to a strong LLC amount feedback. Consequently, initially cold SO models tend to simulate a fast global warming by absorbing more downward shortwave radiation compared to initially warm SO models because more LLC disappears due to a strong LLC amount feedback during the 2°C rise. Our results demonstrate that climate models that correctly simulate initial SO state can improve 2°C warming projections with reduced uncertainties.