Newswise — New calculations from the University of Copenhagen suggest that crucial ocean currents responsible for redistributing heat, cold, and precipitation between the tropics and the northernmost parts of the Atlantic region will cease to function around 2060 if greenhouse gas emissions persist at current levels. This finding contradicts the latest report from the IPCC.
Contrary to common assumptions about climate change's impact on Europe, a chilling future might be on the horizon. Researchers from the University of Copenhagen's Niels Bohr Institute and Department of Mathematical Sciences have conducted a study revealing that the ocean current system, vital for exchanging cold and heat between the North Atlantic region and the tropics, will entirely collapse if we continue emitting greenhouse gases at the present rate.
Using advanced statistical tools and historical ocean temperature data spanning the past 150 years, the researchers have determined that the ocean current, known as the Thermohaline Circulation or the Atlantic Meridional Overturning Circulation (AMOC), is highly likely to collapse with 95 percent certainty between 2025 and 2095. The most probable timeframe for this event is estimated to be 34 years from now, in 2057. Such a collapse could pose significant challenges, including tropical warming and increased storm activity in the North Atlantic region.
Professor Peter Ditlevsen from the Niels Bohr Institute emphasizes the gravity of this situation, explaining that the shutdown of AMOC could lead to drastic changes in Earth's climate by altering the distribution of heat and precipitation worldwide. While the cooling effect on Europe might appear less severe compared to the overall global warming and frequent heatwaves, the shutdown would exacerbate warming in the tropics, where rising temperatures have already created challenging living conditions.
The study, recently published in the esteemed scientific journal Nature Communications, contradicts the message conveyed by the latest IPCC report, which considered an abrupt change in the thermohaline circulation to be highly improbable during this century. The researchers stress the urgent need for reducing global greenhouse gas emissions as quickly as possible to mitigate these potential consequences.
Early warning signals present
The researchers arrived at their prediction by studying early warning signals exhibited by ocean currents as they approach instability. These Early Warning Signals for the Thermohaline Circulation have been documented in the past, but it is only now, with the development of advanced statistical methods, that they have been able to forecast the timing of a potential collapse.
The team focused on analyzing sea surface temperatures in a specific area of the North Atlantic from 1870 to the present day. These sea surface temperatures act as "fingerprints" that indicate the strength of the AMOC, a circulation system that has only been directly measured for the past 15 years.
Thanks to new and improved statistical tools, Professor Susanne Ditlevsen from UCPH's Department of Mathematical Sciences explains that they were able to perform more robust calculations, leading to a more accurate estimation of when the Thermohaline Circulation might collapse, which was not feasible before.
The Thermohaline Circulation has been operating in its current mode since the last ice age, during which it indeed experienced collapses. Researchers have observed abrupt climate shifts between the present state of the AMOC and the collapsed state, occurring around 25 times in connection with ice age climates. These events, known as Dansgaard-Oeschger events, were initially observed in ice cores from the Greenlandic ice sheet. During these events, the climate experienced extreme changes of 10-15 degrees over a decade, whereas the current climate change is characterized by 1.5 degrees warming over a century.
- The Atlantic Meridional Overturning Circulation (AMOC) plays a vital role in the global system of ocean currents. It is responsible for the most significant part of heat redistribution from the tropics to the northernmost areas of the Atlantic, particularly benefiting Western Europe with its relatively mild climate.
- In the northernmost latitudes, the AMOC facilitates the conversion of surface water into deep, southbound ocean currents. This transformation creates space for additional surface water to be transported northward from equatorial regions. This thermohaline circulation is of utmost importance in maintaining the temperate climate of the North Atlantic region.
- The research on AMOC and its potential collapse is supported by TiPES, a collaborative European research initiative dedicated to studying tipping points in the climate system. Funded by EU Horizon 2020, the TiPES project brings together interdisciplinary expertise to explore critical climate tipping points.