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Publication Date
11 March 2024

Sea-Surface Temperature Pattern Effects Have Slowed Global Warming and Weakened Constraints on the High End of Climate Sensitivity

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Researchers used four different lines of evidence to estimate the impact of the surface warming pattern on historical global warming rates—the so-called “pattern effect.” All lines of evidence show that the observed warming pattern has slowed global warming relative to what would have been expected under the more uniform warming pattern that coupled models simulate.


The failure of climate models to reproduce the recent (1981 – 2014) pattern of warming introduces substantial uncertainty into projections of future climate change. The findings suggest that observed warming over recent decades provides little information on the high-end of climate sensitivity. Thus, information about the likelihood of very high levels of warming must come from other lines of evidence.


Researchers used CMIP5/6 models to show that the inter-model relationship between satellite-era warming (1981 – 2014) and metrics of climate sensitivity arises from a similarity in transient and equilibrium warming patterns within the models, producing an effective climate sensitivity (EffCS) governing recent warming that is comparable to the value of ECS governing long-term warming under CO2 forcing.

However, CMIP5/6 historical simulations do not reproduce the observed pattern of warming. When driven by observed sea surface temperature changes, even high ECS models produce low EffCS values consistent with the observed global warming rate.

The inability of CMIP5/6 models to reproduce the observed pattern of warming thus results in a bias in the modeled relationship between recent global warming and climate sensitivity. Correcting for this bias means that observed warming is consistent with a wide range of ECS and TCR values that extend to higher values than previously recognized. These findings are corroborated by energy balance model simulations and coupled model (CESM1-CAM5) simulations that better replicate the observed pattern of warming via tropospheric wind nudging or Antarctic meltwater fluxes.

Because CMIP5/6 models fail to simulate observed warming patterns, proposed warming-based constraints on ECS, TCR, and projected global warming are biased low. The results reinforce recent findings that the unique pattern of observed warming has slowed global mean warming over recent decades and that how the pattern will evolve in the future represents a major source of uncertainty in climate projections

Point of Contact
Cristian Proistosescu
University of Illinois at Urbana-Champaign
Funding Program Area(s)
Sea-surface temperature pattern effects have slowed global warming and biased warming-based constraints on climate sensitivity
Armour, Kyle C., Cristian Proistosescu, Yue Dong, Lily C. Hahn, Edward Blanchard-Wrigglesworth, Andrew G. Pauling, Robert C. Jnglin Wills, et al. 2024. “Sea-Surface Temperature Pattern Effects Have Slowed Global Warming And Biased Warming-Based Constraints On Climate Sensitivity”. Proceedings Of The National Academy Of Sciences 121 (12). Proceedings of the National Academy of Sciences. doi:10.1073/pnas.2312093121.