In the 2004 film The Day After Tomorrow, humanity is plunged into a nightmarish international storm that sends the planet into a new ice age, the Daily Mail recalls. And although the blockbuster has been relegated to the realm of science fiction, the science behind the frightening scenario is true.
Experts say that within a few years, melting glaciers could block the Gulf Stream, a system of currents that brings heat to the northern hemisphere. Without this additional heat source, average temperatures could drop several degrees in North America, parts of Asia and Europe, and people would face "severe and cascading impacts around the world."
An abrupt halt to Atlantic Ocean currents looks more likely than ever, scientists warn, as computer modeling shows a "cliff-like" tipping point looming in the near future.
The study authors from Utrecht University in the Netherlands don't know exactly when the collapse will occur, although previous research suggested it would happen as early as next year. “We are approaching a collapse, but we are not sure by how much,” said lead author René van Westen, a climate scientist and oceanographer at Utrecht University. “We are moving towards a tipping point.”
When a global weather disaster like the one the day after tomorrow might occur is "the million-dollar question," van Westen said.
"Unfortunately, we can't answer that at the moment," he said. "It also depends on the rate of climate change that we are causing as humanity."
The Gulf Stream is part of a much larger system of currents officially called the Atlantic Meridional Overturning Circulation, or AMOC.
Described as an "ocean conveyor belt," it transports warm water near the ocean's surface northward from the tropics into the northern hemisphere.
When warm water reaches the North Atlantic (around Europe, the UK and the east coast of the US), it loses heat and freezes. As this ice forms, salt remains in the ocean water, explains the Daily Mail. Due to the large amount of salt in the water, it becomes denser, settles and is carried south, to a lower depth. Eventually, the water rises back to the surface and heats up in a process called upwelling, completing the cycle.
Scientists believe the AMOC is bringing enough heat to the northern hemisphere that without it, much of Europe would be subject to a deep freeze.
Previous studies have already shown that AMOC is slowing due to climate change.
The engine of this conveyor is located off the coast of Greenland, where as more ice melts due to climate change, more fresh water is flowing into the North Atlantic, slowing everything down.
A new study predicts that a dramatic AMOC shutdown could occur in the next few decades, rather than the next few centuries as previously thought.
The researchers developed a computer simulation in which they were able to measure the sudden weakening of ocean circulation.
The simulation resulted in fresh water entering the Atlantic Ocean and, as a result, the strength of the circulation gradually decreased until it reached a critical "tipping point" and ceased.
The results predict that Europe's climate will cool by about 1.8°F (1°C) per decade, and some regions will even see cooling of more than 5.4°F (3°C) per decade—much faster than Today's global warming is about 0.36 °F (0.2 °C) per decade.
In addition to plunging countries into a deep freeze, this would cause Arctic ice to spread further south, increase heat in the southern hemisphere, change global rainfall patterns and destroy the Amazon rainforest.
Other scientists say it would be a disaster that could cause food and water shortages around the world. “We found that once it reaches a tipping point, the conveyor belt shuts down within 100 years,” the authors say. “Heat transfer to the north is greatly reduced, leading to dramatic climate shifts.”
The only thing they have not been able to determine is when exactly this tipping point will be reached, although it is still at least decades away, if not more.
"The study provides compelling evidence that the AMOC is approaching a tipping point, based on a robust, physically based early warning indicator," said Tim Lenton, chair of climate change at the University of Exeter, who was not involved in the study. What it can't (and doesn't) say is how close the tipping point is, because that shows there isn't enough data to make a statistically reliable estimate of that."
The study was published in the journal Science Advances.