Flux continu

On why collapse could be much closer than predicted: what happens when the Atlantic Ocean’s heart stops beating?

The idea that the AMOC is headed to collapse is very controversial, but it is clearly weakening. If the circulation did collapse, the consequences on both sides of the Atlantic Ocean would be immense—including large changes in temperature and a spike in weather-related disasters.

The Atlantic Meridional Overturning Circulation is the main driver of northward heat transport in the Atlantic Ocean today, setting global climate patterns. Whether global warming has affected the strength of this overturning circulation over the past century is still debated: observational studies suggest that there has been persistent weakening since the mid-twentieth century, whereas climate models systematically simulate a stable circulation. Here, using Earth system and eddy-permitting coupled ocean–sea-ice models, we show that a freshening of the subarctic Atlantic Ocean and weakening of the overturning circulation increase the temperature and salinity of the South Atlantic on a decadal timescale through the propagation of Kelvin and Rossby waves. We also show that accounting for upper-end meltwater input in historical simulations significantly improves the data–model agreement on past changes in the Atlantic Meridional Overturning Circulation, yielding a slowdown of 0.46 sverdrups per decade since 1950

There is increasing concern that the Atlantic Meridional Overturning Circulation (AMOC) may collapse this century with a disrupting societal impact on large parts of the world. Preliminary estimates of the probability of such an AMOC collapse have so far been based on conceptual models and statistical analyses of proxy data. Here, we provide observationally based estimates of such probabilities from reanalysis data. We first identify optimal observation regions of an AMOC collapse from a recent global climate model simulation. Salinity data near the southern boundary of the Atlantic turn out to be optimal to provide estimates of the time of the AMOC collapse in this model. Based on the reanalysis products, we next determine probability density functions of the AMOC collapse time. The collapse time is estimated between 2037-2064 (10-90% CI) with a mean of 2050 and the probability of an AMOC collapse before the year 2050 is estimated to be 59±17%.

Assisterons-nous au collapse de la civilisation techno-industrielle avant que des supraintelligences artificielles ne gouvernent le monde ?

Comprendre les enjeux du réchauffementL'état des connaissances sur les changements climatiques, leurs causes et leurs impacts sont évalués depuis plus de 30 ans par le Groupe d'Experts Intergouvernemental sur l'Évolution du Climat : le GIEC. La principale mission de ces scientifiques est de se partager la lecture de toutes les études et de les synthétiser sans aucun parti pris. Surtout, le GIEC met ses rapports à disposition des décideurs politiques et du grand public. Pourtant nous sommes nombreux et nombreuses à en ignorer les contenus ou ne pas savoir comment s'emparer des connaissances de ces rapports. C’est le cas de Xavier lorsqu’il croise Iris, jeune docteure en sciences du climat qui va le guider à la rencontre de neuf experts, auteurs et autrices de certains de ces rapports. Xavier va peu à peu changer sa façon de voir le monde et passer par toutes ces émotions qui accompagnent notre douloureuse et nécessaire prise de conscience (choc, déni, colère, acceptation…) sur ce sujet majeur du changement

Les climatologues souffrent-ils de l’indifférence autour de leur travail ? Iris Dion leur donne la parole dans la bande dessinée « Horizons climatiques », qui mêle vulgarisation scientifique et réflexions intimes.

Concevoir et organiser des sociétés du bien-vivre durables, et résister, s’adapter, régénérer. Un plan en 3 étapes pour un monde nouveau, expliqué par Cyril ...

Wereldnieuws was het de laatste weken. ‘De Golfstroom kan stilvallen in 2025’, kopten kranten naar aanleiding van een recent verschenen paper. In feite ging de publicatie niet over de Golfstroom, maar over de Atlantic Meridional Overturning Circulation, kortweg AMOC. En bij de genoemde termijn vallen ook vraagtekens te plaatsen. Wat zegt de wetenschap over al die amok rond de AMOC? ‘Of het nu in 2025 is of in 2100, we willen niet dat dit gebeurt.’

The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system and a future collapse would have severe impacts on the climate in the North Atlantic region. In recent years weakening in circulation has been reported, but assessments by the Intergovernmental Panel on Climate Change (IPCC), based on the Climate Model Intercomparison Project (CMIP) model simulations suggest that a full collapse is unlikely within the 21st century. Tipping to an undesired state in the climate is, however, a growing concern with increasing greenhouse gas concentrations. Predictions based on observations rely on detecting early-warning signals, primarily an increase in variance (loss of resilience) and increased autocorrelation (critical slowing down), which have recently been reported for the AMOC. Here we provide statistical significance and data-driven estimators for the time of tipping. We estimate a collapse of the AMOC to occur around mid-century under the current scenario of future emi