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Could ‘the Day After Tomorrow’ really happen?

The Day After Tomorrow The Day After Tomorrow
13 Oct
2015
In the film The Day After Tomorrow, one of the world’s vital ocean currents suddenly collapses, sending the northern hemisphere into a new ice age. New climate models show the repercussions that may occur following such an event

When Roland Emmerich’s The Day After Tomorrow was released in 2004, its mixture of science and fiction caused a stir. The film’s disaster montage of super storm-waves crashing through New York City, serial tornadoes in Los Angeles and an Ice Age in Europe alarmed viewers and irritated scientists, given that they occurred at an impossible pace. However, the change of the northern hemisphere’s climate to a colder reality ‘is not unrealistic’ says Professor Sybren Drijfhout, a researcher from the University of Southampton and lead author of a new report that explores some of the real science behind the Hollywood fiction.

Fundamentally, the movie exaggerates what could happen to the northern hemisphere if a vital current in the great ocean ‘conveyor belt’ – the Atlantic Meridional Overturning Circulation (AMOC) – were to collapse as a result of global warming. Using one of the leading climate models in the world, the ECHAM5 from the Max-Planck Institute for Meteorology, Drijfhout has researched would possible outcomes for the northern hemisphere should the AMOC collapse.

‘The effects in terms of climate change are exaggerated in the movie,’ he tells Geographical. ‘Actually, northwest Europe would experience climate conditions similar to the Little Ice Age in the late Middle Ages, not similar to the real ice ages, but this would still be a serious business, affecting hundreds of millions of people.’

The AMOC functions when cold, salty Atlantic water reaches the north and sinks (due to salt water being more dense), allowing warmer water from the south to take its place in a continuous cycle. This movement carries heat northward, and plays a vital role in maintaining the current climate. In theory, a sudden injection of ice meltwater from Greenland would prevent the salt water from sinking and disrupt the cycle.

diagram2This diagram shows the larger extent of the great ocean ‘conveyor belt’. At the top, the Deep Water Formation at the Labrador and Nordic seas can be seen. This is where near-surface salt water becomes colder, denser and sinks to allow warmer water to take its place. (Image: Kulhbrodt et al.)

It is the longer climate repercussions of a collapsed AMOC that Drijfhout is most interested in. By the end of the film, the current’s collapse has frozen the northern US states and most of Europe. According to the research, if the AMOC collapsed would ‘obliterate’ global warming for a period of 15 to 20 years. After these years of cooling, global warming would begin to resume – with Europe’s Atlantic coast taking the longest to recover. ‘Planet Earth recovers from the AMOC collapse in about 40 years when global warming continues at present-day rates,’ says Drijfhout relating the findings, ‘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.’

Because the UK would likely suffer more from an AMOC collapse than almost every other country in the world (with the exception of Norway and Iceland), the UK government has invested several million pounds in setting up RAPID, a large monitoring program measuring the AMOC since 2004.

Drijfhout also has a warning for the other side of the Atlantic: ‘The northeast coast of the US would suffer an extra sea level rise of about 0.5 to 1 metre which would last as long as the AMOC remains collapsed.’

The report Competition Between Global Warming and an Abrupt Collapse of the AMOC in Earth’s Energy Imbalance was published in Nature: Scientific Reports

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