An unprecedented marine heatwave in the Mediterranean Sea is alarming climate scientists, with parts of the sea currently experiencing sea surface temperatures up to 8°C above normal a spike so extreme that experts describe it as a once-in-a-billion climatological event. The phenomenon, triggered by a persistent heat dome, is being directly linked to the accelerating effects of human-induced climate change.
This marine heatwave, unfolding at the very start of Europe’s summer, has already set record-breaking anomalies, with the Balearic and Tyrrhenian Seas among the worst-affected zones. According to climatologists, the overall sea surface temperature deviations have reached six standard deviations above average, a rarity that signals extreme and highly unusual warming conditions.
Heat domes large zones of high atmospheric pressure are trapping hot air and reducing wind-driven ocean mixing, allowing surface waters to absorb and retain more heat. As a result, marine heatwaves are not just warming the sea but also loading the atmosphere with moisture, which can later translate into catastrophic storms and flash floods.
The UNEP and Severe Weather Europe warn that this surge in sea temperatures can trigger torrential rainfall, flash floods, and landslides especially in coastal regions like Spain, Italy, the Alps, and the western Balkans. The region has seen deadly consequences before: in October 2024, a single night of record rainfall in southeastern Spain claimed over 200 lives.
Researchers also caution that Mediterranean marine heatwaves are becoming more frequent, lasting longer, and growing in intensity. A 2024 study in Aquaculture noted that such events have tripled over the past four decades and now persist 50% longer than before. Between 2015 and 2019 alone, five consecutive marine heatwaves caused mass mortalities across thousands of kilometres of coastline and disrupted a wide range of marine ecosystems.
The ecological consequences are already unfolding with coral die-offs, fish migration disruptions, and loss of biodiversity threatening local livelihoods, particularly in fishing communities. The Mediterranean’s fisheries are facing steadily warming waters, with some regions reporting temperature increases of 0.75°C per decade.
With the Mediterranean already “in its own league” in terms of warming, experts are urging close monitoring throughout the summer. If sea temperatures remain abnormally high, they could significantly influence autumn rainfall patterns, increasing the risk of further extreme weather events.
This record-breaking marine heatwave is yet another indicator of the escalating climate crisis and its increasingly unpredictable impacts on both marine ecosystems and human communities across the Mediterranean region.