A major system of ocean currents is at risk of collapsing as soon as 2025 and likely by the end of the century, a dire harbinger of potential climate tipping points that suggest the planet is on track for severe climate impacts much sooner than scientists had previously predicted.

The Atlantic Meridional Overturning Circulation, of which the Gulf Stream is a part, is a system of currents that moves warm water toward the North Pole and cold water south.

The warming of the oceans and increased flows of freshwater from melting sea ice have already slowed down the circulation of the system; scientists fear an outright collapse that could wreak havoc on climate systems, increasing the incidence of extreme weather events, pushing sea levels higher, accelerating biodiversity collapse, causing northern Europe to experience colder temperatures that could significantly decrease crop yields, and worsening drought in the African Sahel and monsoon regions in Asia.

A new study published Tuesday in Nature Communications from researchers at the University of Copenhagen modeled sea surface temperatures over time to extrapolate when a collapse might occur. The study looked at the current trajectory of rising greenhouse gas emissions and evidence from ice and sediment to determine how the AMOC behaved at other major periods of climate extremes.

While scientists cautioned that conclusions are based on relatively short periods of detailed observed data, and precise impacts of the slowing or outright collapse of ocean currents are not yet well understood, Professor Peter Ditlevsen, one of the study’s authors, said “I think we should be very worried.vThis would be a very, very large change. The AMOC has not been shut off for 12,000 years.”

(The Hill, Daily Beast, New York Times $, CNN, FT $, The Guardian, Axios, NPR)