Weakening Atlantic Current May Heat the Planet, Not Just Cool Europe
New modeling research indicates that past slowdowns of the Atlantic Meridional Overturning Circulation led to global warming, not just regional cooling. The system acts as a planetary heat valve, and its weakening causes heat to accumulate in the ocean rather than being released to the atmosphere. Scientists warn that such past shifts produced warming comparable to a decade of current human emissions.
The new modeling, published in Nature Geoscience, challenges the long-held assumption that heat simply shifted between hemispheres during past climate shifts. Instead, a sluggish AMOC traps warmth within the ocean depths, raising the planet's overall temperature. Lead author Christo Buizert describes the circulation as a planetary heat regulator, where a strong flow releases heat to the atmosphere, but a weak flow causes it to accumulate.
Over the last 2.7 million years, hundreds of weak periods have occurred. The study indicates these past slowdowns generated warming equivalent to roughly a decade of present-day anthropogenic emissions. Buizert cautions that ancient shifts are not a perfect analogue for current changes, yet they offer valuable insights into potential future warming trajectories.
A weakening AMOC could create a stark divide in climate impacts. Northern Europe may face abrupt regional cooling, challenging agriculture and energy systems, while the broader globe could experience accelerated warming, intensifying heatwaves and sea-level rise. Coastal populations and global food security may be disproportionately affected. Scientists and policymakers could need to reassess climate projections, as this hidden oceanic heat accumulation might alter the pace of global temperature rise.