Global oceans reached their highest recorded sea-surface temperature in August 2024, according to climate data [1, 2].
This spike in temperature signals increasing stress on marine ecosystems and suggests a higher likelihood of extreme weather patterns globally. The warming trend threatens biodiversity and alters weather systems that regulate temperatures on land.
The average global sea-surface temperature outside polar regions reached 21.1°C [1]. This figure represents the highest daily average ever recorded in a data series that dates back to 1979 [1, 3].
Experts attribute the record to a combination of ongoing climate change and a strong El Niño event. A reporter said that the record is a sign that a "Super El Niño" is ramping up [4].
"The record is another clear signal of an ocean under growing stress," Dr. Samantha Burgess said [2].
The warming is not limited to a single region. The Mediterranean Sea also reached its highest surface temperature ever recorded [5]. While the phenomenon is global, the UK is highlighted as an area facing potential impacts from these shifting ocean temperatures [3].
Ocean warming typically leads to more intense storms and disrupts the currents that move heat around the planet. As the water absorbs more heat, it expands, contributing to rising sea levels and threatening coastal infrastructure. The interaction between the El Niño cycle and long-term warming creates a compounding effect on the environment [3, 4].
“The record is another clear signal of an ocean under growing stress.”
The intersection of a cyclical El Niño event with a long-term warming trend indicates that natural climate oscillations are now occurring on a higher baseline of heat. This increases the frequency and intensity of marine heatwaves, which can cause mass coral bleaching and collapse local fisheries, while simultaneously fueling more powerful atmospheric storms.
