In the 2004 climate-change disaster flick “The Day After Tomorrow,” increased greenhouse gases in the atmosphere have a paradoxical effect: Rather than heating up the planet, they trigger a sudden-onset global ice age. The movie was very silly and unscientific, but there was a kernel of truth at the core of it:  The Earth really does have a massive, hidden air-conditioning system that messes with the climate in paradoxical, unexpected ways and is, in turn, affected by climate change. And a new paper turns to that AC unit to, possibly, answer one of the abiding mysteries of climate change: Why did warming seem to “pause” from the mid-1990s to the early 2000s?

Earth’s air conditioning system is called the Atlantic Meridional Overturning Circulation (AMOC). It’s a massive, looping current that carries warm water over the sea surface toward the North…