Meet Europe’s heat pump: In the North Atlantic, a vast system of swirling currents hauls warm water from the tropics toward Europe, keeping the continent’s climate in a Goldilocks zone — neither too cold nor too hot, just right. This heat pump, known as the Atlantic Meridional Overturning Circulation (AMOC), helps ensure European cities enjoy warmer winters than those in the same latitudes elsewhere — think Madrid and New York City.
Enter climate change: The AMOC has run reliably for millennia. But this is about to change as humans continue heating the planet. Increased rainfall driven by climate change and freshwater from melting ice sheets are diluting the Atlantic ocean, hampering the churn of the currents. The fear is that with enough warming, the AMOC will significantly slow or collapse.
What awaits: If that happens, Europe’s climate would harshen in ways that would make this summer’s extremes seem mild by comparison. Winter temperatures could plunge, storms become more ferocious and droughts more intense. Sea levels would rise further on both sides of the Atlantic, and monsoon seasons in the Amazon and Africa would be thrown into chaos.
Near and far: This won’t happen overnight. A shutdown would unfold over decades, but scientists warn that parts of the system could start failing as early as the 2040s. And while an AMOC collapse was long considered extremely unlikely, a growing number of studies show that the currents are more unstable than previously thought.
Preparing for catastrophe: That’s startling governments into action. We found that countries from Iceland to the Netherlands are beginning to take steps toward grappling with this potential catastrophe, with several countries drawing up assessments, investing in early warning or flagging the threat as a national security risk.
No time to waste: The AMOC may never collapse, but that’s no reason for government to twiddle their thumbs, say policymakers and scientists. “It is irresponsible to wait for absolute certainty before preparing,” Jóhann Páll Jóhannsson, Iceland’s climate minister, told us. “Because, by the time the consequences become undeniable, it may already be too late to prevent them from happening.” The full long read is here.