Mounting evidence suggests AMOC may be nearing a tipping point, with one senior researcher revising collapse odds from 5% to above 50%.
Key Takeaways
AMOC has slowed roughly 3 Sverdrups since 1950 (20 to 17 Sverdrups); a 2025 paper clocks recent decline at ~1 Sverdrup per decade in the subtropics.
Portmann et al. (April 2026) constrained IPCC models with real Atlantic temperature and salinity data, tightening projections to a 50% weakening by 2100 vs. the IPCC baseline of 30%.
Ditlevsen & Ditlevsen (2023) used statistical early-warning signs in 100+ years of sea surface temperatures to predict a tipping point between 2037 and 2109 if emissions keep rising.
Models run to 2300+ show collapse probability of 25-70% depending on emissions scenario, most often in the early 2200s; short model runs systematically underestimate the risk.
Collapse consequences include a 4C temperature differential across Europe, weakened African and Asian monsoons, and Southern Ocean carbon release – Iceland designated AMOC shutdown a national security threat in November 2025.
Hacker News Comment Review
Commenters are deeply skeptical that any technical or policy intervention will matter; the dominant view is that coordination failure has been locked in since at least Stommel’s 1961 paper.
Techno-optimism drew direct criticism, with the argument that market incentives structurally cannot address macro climate systems at this scale.
Notable Comments
@AndrewKemendo: traces AMOC warnings to Stommel 1961 and argues global emissions trajectory makes stabilization targets meaningless.
