'The Day After Tomorrow': Could It Really Happen?

In 2004, the film "The Day After Tomorrow" depicted a collapse of the Atlantic meridional overturning circulation, or AMOC, leading to the utter destruction of several major cities and areas, including the freezing of the northern hemisphere, that served as the movie's main plot.

Scientists at first criticized the film's accuracy of climate science, but the scenario of a major AMOC collapse occurring simultaneously with global warming had never been assessed, until now.

Professor Sybren Drijfhout, of the University of Southampton's Ocean and Earth Science department, used the German climate model ECHAM to simulate anthropogenic greenhouse warming alongside an AMOC collapse. Drijfhout found that for a 20-year period, the earth would actually cool instead of warm if the events occurred at the same time.

"The planet earth recovers from the AMOC collapse in about 40 years when global warming continues at present-day rates, but near the eastern boundary of the North Atlantic (including the British Isles) it takes more than a century before temperature is back to normal," Drijfhout said, according to a release.

In his study, Drijfhout saw that global warming would continue after the collapse, as if nothing had happened, but the global temperature would be offset by about 0.8°C. So while the development of a half-earth frozen tundra may be an exaggeration, there could be significant changes to climate.

The AMOC causing atmospheric cooling is related to the heat flow from the atmosphere into the ocean, interestingly enough. This effect has been witnessed during the 15-year climate "hiatus" that the globe is claimed to have been on.

"When a similar cooling or reduced heating is caused by volcanic eruptions or decreasing greenhouse emissions the heat flow is reversed, from the ocean into the atmosphere," Drijfhout said. "A similar reversal of energy flow is also visible at the top of the atmosphere. These very different fingerprints in energy flow between atmospheric radiative forcing and internal ocean circulation processes make it possible to attribute the cause of a climate hiatus period."

This most recent period of weak warming, however, cannot give credit to one, single cause. Scientists believe that El Niño may play a role, as it could be altered in the Southern Ocean by shifting and increasing westerly winds.

Drijfhout believes that although atmospheric changes from volcanic activity, aerosol emissions in Asia, and reduced greenhouse gases have played a role, none of them can be given sole attribution.

"Changes in ocean circulation must have played an important role," he added. "Natural variations have counteracted the greenhouse effect for a decade or so, but I expect this period is over now."

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