Sea-surface temperature pattern effects have slowed globalwarming and biased warming-based constraints on climatesensitivity

• 成果类型: Article
• 署名作者: Armour, Kyle C.; Proistosescu, Cristian; Dong, Yue; Hahn, Lily C.; Blanchard-Wrigglesworth, Edward; Pauling, Andrew G.; Wills, Robert C. Jnglin; Andrews, Timothy; Stuecker, Malte F.; Po-Chedley, Stephen; Mitevski, Ivan; Forster, Piers M.; Gregory, Jonathan M.
• 署名单位: University of Washington; University of Washington Seattle; University of Washington; University of Washington Seattle; University of Illinois System; University of Illinois Urbana-Champaign; University of Colorado System; University of Colorado Boulder; University of California System; University of California San Diego; Scripps Institution of Oceanography; University of Otago; Swiss Federal Institutes of Technology Domain; ETH Zurich; Met Office - UK; Hadley Centre; University of Hawaii System; University of Hawaii Manoa; University of Hawaii System; University of Hawaii Manoa; United States Department of Energy (DOE); Lawrence Livermore National Laboratory; Columbia University; University of Leeds; University of Reading; UK Research & Innovation (UKRI); Natural Environment Research Council (NERC); NERC National Centre for Atmospheric Science
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12383
• DOI: 10.1073/pnas.2312093121
• 发表日期: 2024-03-19
• 关键词: energy budget constraints; ocean heat uptake; climate sensitivity; emergent constraints; southern-ocean; global cloud; variability; dependence; feedback; IMPACT

摘要

The observed rate of global warming since the 1970s has been proposed as a strongconstraint on equilibrium climate sensitivity (ECS) and transient climate response(TCR)-key metrics of the global climate response to greenhouse-gas forcing. UsingCMIP5/6 models, we show that the inter-model relationship between warming andthese climate sensitivity metrics (the basis for the constraint) arises from a similarityin transient and equilibrium warming patterns within the models, producing aneffective climate sensitivity (EffCS) governing recent warming that is comparable to thevalue of ECS governing long-term warming under CO2forcing. However, CMIP5/6historical simulations do not reproduce observed warming patterns. When driven byobserved patterns, even high ECS models produce low EffCS values consistent with theobserved global warming rate. The inability of CMIP5/6 models to reproduce observedwarming patterns thus results in a bias in the modeled relationship between recentglobal warming and climate sensitivity. Correcting for this bias means that observedwarming is consistent with wide ranges of ECS and TCR extending to higher valuesthan previously recognized. These findings are corroborated by energy balance modelsimulations and coupled model (CESM1-CAM5) simulations that better replicateobserved patterns via tropospheric wind nudging or Antarctic meltwater fluxes. BecauseCMIP5/6 models fail to simulate observed warming patterns, proposed warming-basedconstraints on ECS, TCR, and projected global warming are biased low. The resultsreinforce recent findings that the unique pattern of observed warming has slowedglobal-mean warming over recent decades and that how the pattern will evolve in thefuture represents a major source of uncertainty in climate projections