Important ocean currents that redistribute heat, cold and precipitation between the tropics and the far north Atlantic region will close by 2060 if current greenhouse gas emissions continue. That’s the conclusion based on new calculations from the University of Copenhagen that contradict the latest report from the Intergovernmental Panel on Climate Change.
Contrary to what we might imagine about the impact of climate change in Europe, there may be a cooler future. In a new study, researchers from the Niels Bohr Institute and the Department of Mathematical Sciences at the University of Copenhagen predicted that the system of ocean currents that currently distributes cold and heat between the North Atlantic region and the tropics will come to a complete halt if we continue to emit the same levels of greenhouse gases as we do today.
Using advanced statistical tools and ocean temperature data from the past 150 years, the researchers calculated that the ocean current, known as the thermohaline circulation or Atlantic meridional circulation (AMOC), will collapse—with 95 percent certainty—between 2025 and 2095. This will happen most likely in 34 years, in 2057, and could lead to significant challenges, particularly warming in the northern tropics and storm surge in the Atlantic.
“A shutdown of the AMOC could have very serious consequences for the Earth’s climate, for example, by changing how heat and precipitation are distributed globally. While the cooling of Europe may seem less severe as the world as a whole becomes warmer and heat waves occur more frequently, such a shutdown would contribute to further warming of the tropics, where higher temperatures have already created difficult living conditions,” says Professor Peter Detlevsen of the Niels Institute.
“Our result underscores the importance of reducing global greenhouse gas emissions as quickly as possible,” says the researcher.
Calculations just published in the scientific journal, nature connections, It contradicts the message in the IPCC’s latest report, which, based on climate model simulations, considers an abrupt change in the thermohaline cycle to be extremely unlikely within this century.
Presence of early warning signs
The researchers’ prediction is based on early warning observations that ocean currents show when they become unstable. these early warning signs The thermohaline cycle has been previously reported, but only the development of advanced statistical methods has made it possible to predict only when collapse will occur.
The researchers analyzed sea surface temperatures in a specific region of the North Atlantic Ocean from 1870 to the present day. These sea surface temperatures are “fingerprints” attesting to the strength of the AMOC, which have only been directly measured over the past 15 years.
“Using new and improved statistical tools, we performed calculations that provide a more robust estimate of when a thermohaline cycle collapse is likely to occur, something we had not been able to do before,” explains Professor Susanne Detlefsen of UCLA’s Department of Mathematical Sciences.
The thermohaline circulation has been operating in its current state since the last Ice Age, when the circulation actually collapsed. Abrupt climate jumps between the current state of the AMOC and the collapsed state are observed 25 times with respect to the ice climate. These are the famous Dansgaard-Oeschger events first observed in the ice cores of the Greenland Ice Sheet. In those events, the climate changes were extreme with changes of 10-15 degrees over a decade, while today the climate changes by about 1.5 degrees over a century.
- The Atlantic Meridian Overturning Circulation (AMOC) is part of a global system of ocean currents. By far, it accounts for the bulk of the redistribution of heat from the tropics to the northernmost regions of the Atlantic region – not least western Europe.
- At northernmost latitudes, circulation ensures the diversion of surface waters into deep, southbound ocean currents. The shift creates space for additional surface water to move north from the tropics. As such, the thermohaline circulation is critical to maintaining the relatively temperate climate in the North Atlantic region.
- The work is supported by TiPES, a joint European research collaboration focused on tipping points in the climate system. The TiPES project is a European Union Horizon 2020 interdisciplinary climate research project focused on tipping points in the climate system.