The Mediterranean Sea recorded record surface temperatures this spring, with an average of 19.7 °C in May [1].
This rapid warming threatens marine biodiversity and indicates a trend of intensifying heatwaves that could destabilize regional ecosystems. Because oceans absorb up to 90% of excess heat from the atmosphere [1], the Mediterranean is acting as a primary sink for global warming effects.
By the end of June, temperatures in several locations across the basin approached 30 °C [2]. These peaks were particularly evident in the western Mediterranean and the coastal waters of Spain and Italy [2]. Such levels are comparable to temperatures typically found in the Caribbean, signaling a shift in the thermal profile of the region.
Long-term data shows the Mediterranean has warmed approximately 1.5 °C since 1982 [1]. This steady increase is driven by global climate change, which produces marine heatwaves that are more frequent, intense, and long-lasting than in previous decades [1], [3].
The warming trend poses a direct threat to critical marine flora. Specifically, the heat is endangering Posidonia, a seagrass species often described as the lung of the Mediterranean [3]. As water temperatures rise, these ecosystems struggle to survive, potentially reducing the sea's capacity to sequester carbon, and support aquatic life.
Climate scientists said that the sea's role in absorbing atmospheric heat creates a feedback loop. While the water buffers the air temperature, the resulting marine heatwaves disrupt the biological cycles of species that cannot adapt to the rapid pace of change [1], [3].
“The Mediterranean has warmed about 1.5 °C since 1982.”
The record warming of the Mediterranean highlights the vulnerability of semi-enclosed seas to climate change. Because these basins heat up faster than open oceans, they serve as early warning systems for the broader global marine environment. The degradation of Posidonia seagrass not only threatens local biodiversity but also impairs the natural carbon sequestration processes essential for mitigating further atmospheric warming.
