12 May 2023
 | 12 May 2023
Status: this preprint is currently under review for the journal ESD.

Multi-centennial evolution of the climate response and deep ocean heat uptake in a set of abrupt stabilization scenarios with EC-Earth3

Federico Fabiano, Paolo Davini, Virna Meccia, Giuseppe Zappa, Alessio Bellucci, Valerio Lembo, Katinka Bellomo, and Susanna Corti

Abstract. Understanding long-term committed climate change due to anthropogenic forcing is key to inform climate policies, yet these timescales are still under-explored. We present here a set of 1000-year long abrupt stabilization simulations performed with EC-Earth3. Each simulation follows a sudden stabilization of the external forcing at the level specified by CMIP6 for historical (1990) or SSP5-8.5 scenario (2025, 2050, 2065, 2080, 2100) conditions, with a final temperature increase ranging between 1.4 and 9.6 K with respect to the pre-industrial baseline. Remarkably, the simulation stabilized at a level of greenhouse gases (GHGs) close to present-day (2025) well exceeds in the long term the Paris agreement goals of 1.5 and 2 degrees warming above pre-industrial, and only the 1990 simulation leads to a stabilized climate below 1.5 degrees warming. We first focus on the evolution of the climate response at multi-centennial timescales and its dependence on the level of forcing. Surface warming patterns evolve during the course of the simulations, with the most striking feature being a drastic acceleration of the warming in the Southern Ocean. The patterns of precipitation change also evolve during the stabilization runs: the drying trends found in the sub-tropical oceans and in Mediterranean-like hotspots in the SSP5-8.5 scenario tend to reduce, or even to reverse. We finally focus on the rate of heat storage in the global ocean, which is the main driver of the climate response at multi-centennial timescales. We find that the rate of warming of the deep ocean is almost independent from the amplitude of the forcing, so that most of the additional heat remains in the upper layers at high forcing. We hypothesize that this is due – at least partly – to a decreased ventilation of the deep ocean, caused by changes in the meridional overturning circulation (MOC). The results highlight the importance of studying multi-centennial timescales of climate change to better understand the response of the deep ocean, which will play a crucial role in determining the final state of the climate system once GHGs concentrations are stabilized.

Federico Fabiano et al.

Status: open (until 02 Jul 2023)

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Federico Fabiano et al.

Federico Fabiano et al.


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Short summary
Even after the concentration of greenhouse gases will be stabilized, the climate will continue to adapt, seeking a new equilibrium. We study this long-term stabilization through a set of 1000-year simulations, obtained by suddenly "freezing" the atmospheric composition at different levels. If frozen at the current state, global warming will likely surpass 3 degrees in the long-term. We then study how climate impacts will change after various centuries and how the deep ocean will warm.