James Hansen: AMOC Could Reach a 'Point of No Return' in 20–30 Years, New Study Warns

37 years after his first warning, James Hansen sounds an urgent alarm over the AMOC

In 1988, then-NASA scientist James Hansen testified to the U.S. Congress that global overheating posed a grave danger. That warning was widely ignored. Now, more than three decades later, Hansen is a lead author on a new international study that finds the risk of a collapse of the Atlantic Meridional Overturning Circulation (AMOC) has likely been underestimated.

Inside Climate News reported that the paper examines accelerating changes over the past 15 years. Where earlier work concluded an AMOC collapse was unlikely this century, the new analysis suggests a shutdown could occur within 20–30 years.

"The main issue is the sleeping giant, the point of no return, the danger of an AMOC shutdown and large sea level rise," Hansen told Inside Climate News.

The AMOC functions like a massive ocean conveyor belt: it moves warm surface waters north and returns colder, deeper waters south. This circulation is extremely slow—NOAA notes that a parcel of water can take more than 1,000 years to complete the full loop.

Why an AMOC collapse matters

• Rapid sea-level rise along the U.S. East Coast and other coastlines would put millions of homes and infrastructure at immediate risk.
• Shifts in the tropical rain belt and atmospheric circulation could sharply reduce crop yields in many regions, threatening food security.
• Western Europe’s mild climate could change to drier summers and much colder winters, with major economic and social impacts.
• An AMOC shutdown would amplify extreme weather events—heat waves, droughts, floods and storms—and reduce society’s capacity to adapt.

The paper reviews policy options such as a carbon fee-and-dividend system and direct measures to cut short-lived but powerful pollutants. The authors call for intensified research into both technical interventions and social strategies to raise public awareness. In their conclusion, Hansen and colleagues criticize how special interests have obstructed science-informed solutions and how political failures have allowed risks to grow.

Despite the seriousness of the findings, the paper closes on a cautiously hopeful note: the authors express faith in a new generation of leaders and in civic engagement—especially among young people—as essential to pursuing effective climate action.

"Why am I optimistic that we can succeed? Young people have demonstrated an extraordinary ability to affect politics without taking any money from special interests," the paper says.

Note on uncertainty: While the new analysis raises the probability of a relatively near-term AMOC shutdown, substantial scientific uncertainty remains about exact timing and regional impacts. The study calls for urgent research to better constrain risks and policy responses.