From Europe’s extreme summer to a wider climate-system risk
Recent heat, drought and wildfire conditions across Europe have raised fresh alarm about the effects of climate change. But these risks should no longer be surprising. Climate scientists have warned for decades that rising greenhouse-gas emissions would make heatwaves more frequent, longer and more intense, worsen drought conditions, and increase the likelihood of dangerous fire weather.
That warning is now visible across Europe. According to the Copernicus Climate Change Service (C3S, 2026) June 2026 was the hottest June recorded in western Europe averaging 20.74C, which is 3.06C above the 1991-2020 average. Maximum temperatures reached 40 degrees in almost half the country of France during the first and second heatwaves in June and July respectively. Drought conditions across most of Europe are assessed as critical by the European Drought Observatory.
As of the beginning of August, most major European rivers, including the Rhine and the Danube, are reaching record low levels, creating major disruption to the agricultural, commercial, tourist and energy industries (The Guardian, 2026). In extreme heat and drought conditions, bushfires are raging across Europe. In France, a record-breaking fire near Bordeaux forced the evacuation of more than 200,000 people while burning approximately 42,000 hectares. The European Forest Fire Information System reports that more than 90,000 hectares have already burned in France alone this year, making it already the highest yearly total since 2006, with a couple of more months of summer to go.
These events are not evidence that every climate projection is unfolding exactly as forecast. They are evidence that well-understood physical risks become far harder and more expensive to manage once they are already occurring.
A quieter but potentially larger risk
Less visible than fires or heatwaves is the gradual change occurring in the Atlantic Meridional Overturning Circulation, or AMOC.
The AMOC is a major system of Atlantic currents that transports heat, freshwater and nutrients around the ocean (Risk Frontiers, 2022). It influences Europe’s climate, tropical rainfall and monsoon systems, regional sea levels and marine ecosystems. A major weakening or shutdown would not simply make Europe colder by ushering an ice age. It could reorganise rainfall and temperature patterns across large parts of the world, with consequences for agriculture, water security, ecosystems, infrastructure and global supply chains that would be an order of magnitude greater than those occurring this summer in Europe.
The science has increasingly pointed towards AMOC weakening under continued warming. The main uncertainties concern the scale, timing and speed of that decline, and whether it would occur gradually or through a more abrupt transition.
Two recent studies illustrate that uncertainty. Mehling et al. (2026) simulate severe but gradual weakening under very high emissions and find that additional Greenland meltwater makes the decline stronger, particularly after 2100, without necessarily making it abrupt or irreversible. Figure 1 shows that cutting off the meltwater supply does not restore the AMOC transport but ramping down CO2 emission does restore the circulation to levels even higher than seen today.
The study by Holden et al. (2026, in prep) estimates a material probability that the AMOC may already be committed to a future collapse, with that probability rising substantially the longer high emissions continue. Figure 2 shows that even if CO2 emissions were to drastically reduce from a 2025 peak, there is a 10% probability that the AMOC would be close to shutdown by 2150. Their results suggest that simulations that do not capture a shutdown of the AMOC still show a slowdown of about 15% on average by 2100. The authors also show that if a decrease of emissions were to be delayed, this would increase the probability of AMOC shutdown, reaching 80% if emissions are not reduced before 2100. That study is still under review, so its exact probabilities should be treated cautiously.
Although these studies differ in their models, assumptions and conclusions about exactly how the decline may unfold, both accept the central direction of change: under continued high-emissions scenarios, significant AMOC weakening is expected. Moreover, this is not just a result shared by these two recent studies but is reaching consensus in the scientific community.
Emissions choices still matter
Both studies also point to the same practical conclusion that reducing CO2 emissions can reduce the risk of AMOC collapse and even restore its strength.
Mehling et al. (2026) show that the AMOC gradually recovers when emissions are strongly reduced, regardless of the influence of Greenland meltwater input. The recovery takes decades to centuries and is based on an idealised scenario, but it shows that the trajectory is influenced by cumulative emissions rather than being automatically irreversible.
Meanwhile, Holden et al. (2026) find that delaying peak emissions increases the probability of becoming committed to a future shutdown. It also suggests that continued emissions can shorten the interval between crossing that point of commitment and the eventual physical collapse.
The precise estimates remain uncertain, but the risk relationship is clear: earlier and stronger emissions reductions improve the odds of avoiding an AMOC shutdown.
Risk implication
Europe’s current summer conditions demonstrate the cost of responding only after a climate hazard becomes obvious. Heat, drought and wildfire risks were identified long before they became recurring operational and financial problems.
The same mistake should not be repeated with larger climate-system risks. We may not know exactly when or how rapidly the AMOC will decline, but science is showing us the direction of change, the potential consequences and the factor increasing the risk.
For risk managers, uncertainty is not a reason to wait. It is a reason to prepare, reduce exposure and act before the available options narrow. For decision makers, the task now is to stop treating climate impacts as unexpected emergencies and start managing them as foreseeable, systemic risks.
References
The Guardian, Europe’s rivers are running dry and the knock-on effects are disastrous, 2026. https://www.theguardian.com/commentisfree/2026/aug/05/europe-rivers-running-dry-catastrophe-danube-rhine, accessed Aug 2026
Copernicus Climate Change Services. https://climate.copernicus.eu/copernicus-record-heatwave-brings-hottest-june-western-europe-during-second-warmest-june-globally, accessed Aug 2026
Risk Frontiers. How Potential Changes of a Slow, Deep Current in the Atlantic will Intensify Extreme Weather in Eastern Australia, 2022. https://riskfrontiers.com/insights/potential-impact-slowing-amoc-lanina-weather-eastern-australia/.
Holden, P.B., Abrams, J.F., Bieger, M., Lenton, T.M., Mercure, J.-F., Semieniuk, G. and Sharpe, S. (2026), Quantifying the probability of committed AMOC collapse, EarthArXiv preprint.
Mehling, O., Bellomo, K., Fabiano, F., Devilliers, M., Petrini, M., Corti, S. and von Hardenberg, J. (2026), ‘Limited impact of Greenland meltwater on abruptness and reversibility of future Atlantic overturning changes’, Science Advances, 12(25), eaed2633. DOI: 10.1126/sciadv.aed2633
