World's Oceans Hit Their Hottest Temperature Ever Recorded

The world's oceans have reached their highest temperature ever recorded, new data shows. Scientists say that human-caused climate change and a growing weather pattern called El Niño are both to blame. The average surface temperature of the seas outside the polar regions hit 21.1°C (70°F) on Saturday. That number comes from the European Copernicus Climate Change Service, which tracks ocean temperatures around the globe.

This new record just barely beats the previous high of 21.09°C, which was set on three separate days in March 2024. What makes this extra surprising is when it happened — August is not normally the hottest time for ocean temperatures. Oceans usually reach their warmest point each year in March or April, at the end of summer in the southern hemisphere. Scientists say the fact that temperatures are this high in August is a serious warning sign.

El Niño is a natural weather event that pushes unusually warm water to the surface of the eastern and central tropical Pacific Ocean. When so much ocean water warms up at once, it causes average global temperatures to rise too. Scientists expect El Niño to keep getting stronger until around Christmas, and some say it could be the strongest in hundreds of years. That means ocean temperatures could keep climbing all the way into 2027.

What worries scientists most is that the oceans are already this hot even before El Niño reaches its peak. Dr. Samantha Burgess, deputy director of Copernicus, explained the situation clearly. "El Niño is adding heat to the system, but it is doing so on top of decades of human-driven warming," she said. In other words, El Niño is making an already bad problem even worse.

The oceans absorb more than 90% of the extra heat that gets trapped by greenhouse gases. These gases are released mainly by burning fossil fuels like coal, oil, and natural gas. As the oceans soak up this heat, they warm up more and more over time. Scientists say this is the main reason that ocean temperatures keep breaking records year after year.

Warmer oceans cause serious problems for people and wildlife around the world. They can make storms stronger by giving them more moisture and energy to grow. They also cause sea levels to rise, because warmer water takes up more space — and higher seas mean a greater risk of flooding in coastal areas. In addition, extreme ocean heat can destroy important sea habitats like coral reefs.

Ocean heat is not just a problem in the Pacific. Large areas of the seas around the United Kingdom and Europe have been experiencing marine heatwaves for much of this year. A marine heatwave is a long stretch of time when the ocean is much hotter than normal. Dr. Burgess warned that these heatwaves are putting increasing pressure on marine ecosystems and the communities that depend on them.