Climate paradox: Ocean current collapse could plunge Europe into cold

A prediction from scientists at the University of Copenhagen presents a somewhat paradoxical outcome of our continued reliance on greenhouse gas-emitting energy sources. The experts warn that critical ocean currents – which carry heat, cold, and precipitation between the tropics and the far reaches of the Atlantic region – may come to a grinding halt around 2060 if greenhouse gas emissions continue at the current rate. 

This latest calculation contradicts earlier reports from the Intergovernmental Panel on Climate Change (IPCC).

Atlantic ocean current system

As Europe braces for the impacts of climate change, one might envision its future to be scorching. However, this recent study from researchers at the Niels Bohr Institute and the Department of Mathematical Sciences at the University of Copenhagen paints a different picture. 

The experts forecast that the Thermohaline Circulation, or the Atlantic Meridional Overturning Circulation (AMOC), the ocean current system that regulates the distribution of heat and cold between the North Atlantic region and the tropics, will cease to function entirely if the rate of greenhouse gas emissions remains unchanged.

Shutting down the AMOC

By leveraging sophisticated statistical tools and analyzing ocean temperature data spanning the last century and a half, the researchers determined that, with a 95 percent certainty, the AMOC will collapse sometime between 2025 and 2095. 

The most likely time frame for this dramatic event is 34 years from now, in 2057, an event that will pose substantial challenges, from amplified warming in the tropics to a surge in storminess in the North Atlantic region.

“Shutting down the AMOC can have very serious consequences for Earth’s climate, for example, by changing how heat and precipitation are distributed globally,” said Professor Peter Ditlevsen from the Niels Bohr Institute.

“While a cooling of Europe may seem less severe as the globe as a whole becomes warmer and heat waves occur more frequently, this shutdown will contribute to an increased warming of the tropics, where rising temperatures have already given rise to challenging living conditions.”

“Our result underscores the importance of reducing global greenhouse gas emissions as soon as possible.”

IPCC report findings

These calculations, recently published in the journal Nature Communications, throw into question the conclusions of the latest IPCC report, which deemed a sudden change in the thermohaline circulation unlikely within this century based on climate model simulations.

The researchers derived their predictions from early warning signals exhibited by ocean currents as they begin to destabilize. The appearance of these Early Warning Signals for the Thermohaline Circulation has been reported before. However, it is the recent advancements in statistical methods that have finally made it possible to predict the precise timing of a potential collapse.

Focusing on sea surface temperatures in a particular region of the North Atlantic from 1870 to the present day, the researchers determined these temperatures to be “fingerprints” of the AMOC’s strength, which has been directly measured only in the past 15 years.

Collapse of the Thermohaline Circulation

“Using new and improved statistical tools, we’ve made calculations that provide a more robust estimate of when a collapse of the Thermohaline Circulation is most likely to occur, something we had not been able to do before,” explained Professor Susanne Ditlevsen of the Department of Mathematical Sciences at the University of Copenhagen.

The thermohaline circulation has remained in its current mode since the last ice age, during which it had collapsed. This collapse, known as Dansgaard-Oeschger events, observed in ice cores from the Greenlandic ice sheet, has occurred 25 times in association with ice age climates. 

These events were accompanied by extreme climate changes, with temperatures shifting 10-15 degrees within a decade. In contrast, climate change today is characterized by a 1.5 degree warming over a century. With the threat of another such collapse, the urgency to mitigate greenhouse gas emissions becomes all the more critical.

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