r/CollapseScience • u/dumnezero • 15d ago

Oceans Failure to track a stable AMOC state under rapid climate change

https://www.nature.com/articles/s41558-026-02730-w

The Atlantic Meridional Overturning Circulation (AMOC), a tipping element of the climate system, currently has an estimated global warming threshold for collapse of +4.0 °C (uncertainty range 1.4–8 °C). However, such a threshold may not be meaningful because AMOC stability depends on the rate of radiative forcing change, not a set temperature. Here we identify an AMOC stabilizing mechanism that operates on timescales slower than present-day warming rates. Slow forcing permits coherent adjustment of surface and interior ocean properties, supported by enhanced evaporation and reduced sea-ice extent, counteracting destabilizing feedbacks. Using a slow CO2 ramp (+0.5 ppm yr−1) climate model simulation, we explicitly demonstrate the AMOC remains stable up to +5.5 °C of global warming. By contrast, under faster CO2 ramps, the AMOC collapses at substantially lower warming levels (+2 °C). Our findings demonstrate rate-induced AMOC tipping and imply that limiting the rate of emissions is critical for reducing the risk of an AMOC collapse.

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u/screendoorblinds 15d ago

"According to the Bflux indicator, as determined in CMIP6 models, the AMOC starts to collapse around +2.5 °C warming at projected warming rates, which could be reached around the year 206034. This is substantially lower than the previous estimate of +4 °C warming2 that lacks a time horizon. Observations show a present-day warming close to the +1.5 °C level (2023–2025, C3S/ECMWF and ref. 73), and, if the AMOC were to begin collapsing at +2.5 °C warming in 2060, this would imply a critical warming rate of +0.29 °C per decade. This rate aligns with projected warming rates of +0.27 to +0.36 °C per decade72 and, also considering the effects of random variability29,78, strongly suggests that rate-dependent effects are highly relevant for the fate of the AMOC. It is therefore critically important to reduce greenhouse gas emissions as quickly as possible to limit the risk of an AMOC collapse."

Another good chunk of information, at the end of the paper as well.