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Fram Strait and the waters to the south, in the Greenland, Norwegian, and Irminger seas, make up the control room of a global “conveyor belt” of currents that stretches the length of the planet. Only in this region and one other, in the Antarctic, does water at the sea surface become heavy enough—dense with cold and salt—to sink all the way to the seafloor and race downhill along the deepening ocean bottom. That sinking powers the conveyor, known as the Atlantic meridional overturning circulation, or AMOC—which in turn regulates temperatures and weather around the world.

A new report warns that the AMOC is one of nine critical climate systems that greenhouse-gas-fueled warming is actively pushing toward a tipping point. Crossing that threshold in one of these systems could trigger rapid and irreversible changes that drive other systems over the edge—leading to a global tipping cascade with catastrophic consequences for the planet. The analysis, released last week in Nature by an international group of leading climate scientists, says the tipping point risks are greater than most of us realize.

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