Icelandic government officials recently met to discuss a dramatic scenario: what if the current that circulates Atlantic waters weakened significantly, or collapsed altogether?

The ocean currents are changing, with major implications for climate around the world. Yet our new research suggests most governments are not preparing for this possibility. Of 91 national adaptation plans submitted to the UN climate convention, only two even mention that key Atlantic current, and neither sets out concrete action in response to its possible collapse.

The Atlantic Meridional Overturning Circulation, or Amoc, is part of the giant conveyor belt of ocean currents that moves warm surface water northward in the Atlantic and sends colder deep water back south. It plays a critical role in regulating the global climate by redistributing heat around the planet, influencing weather patterns and temperatures far beyond the Atlantic basin.

As the climate warms, the Amoc is weakening, and could continue to do so throughout this century. While a full collapse, in which major ocean currents completely reorientate, is unlikely before 2100, a recent study projected a 50% weakening of the Amoc by the end of the century under an intermediate emissions scenario. A collapse would not be unique in geological history. Studies show that the Amoc has undergone dramatic changes before, including a near-complete shutdown around 17,500 years ago, after the coldest period in the last ice age.

A slowdown or collapse would have major implications for temperature and rainfall around the world. In northern........

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