The Oceans Are Running a Fever
The oceans absorb more than 90 percent of the excess heat trapped by greenhouse gases from burning fossil fuels. That heat doesn’t stay locked away; it’s coming ashore, driving record-breaking temperature extremes on land. In the northern hemisphere, barely into summer, heatwaves are shattering records. The European Union’s Copernicus Climate Change Service reported that June 2026 was the hottest June on record for the world’s oceans. Nearly 40 percent of the global ocean area is experiencing a marine heatwave, with patches in the Mediterranean Sea and the Pacific Ocean more than 10 degrees Fahrenheit hotter than usual. This ocean warming, which began accelerating in 2023, has already fueled devastating cyclones and damaged the majority of Earth’s coral reefs.
How Ocean Heat Drives Extreme Weather
Heatwaves on Land
In the United States, dozens of cities endured their hottest Fourth of July celebrations, with temperatures exceeding 100°F. In New Jersey alone, dozens of deaths were linked to the heat over the weekend. European authorities attributed thousands of deaths during the last week of June to heat-related causes. “Heat is one of the features of climate change that has already arrived,” said Ruth Engel, a data scientist at the World Resources Institute. “It’s not something we need to prepare for 25 years from now. It’s already a deadly health issue now.” Engel added that last year, more people died from extreme heat in Europe than from road crashes.
Zachary Labe, a scientist at Climate Central, explained that scientists use early clues to link weather events to ocean heatwaves. For instance, the recent European heatwaves are likely tied to extra‑warm Mediterranean Sea temperatures. High humidity and temperatures in Florida—prompting heavy air‑conditioner use—are probably connected to a marine heatwave with water near 90°F off the state’s Gulf coast. Unusually warm Pacific waters may have set up a weather pattern driving a potentially record‑breaking heatwave forecast for the central and northern U.S. in the coming week.
Supercharging Storms and Rainfall
Hotter air makes the atmosphere “spongier,” holding about 7 percent more moisture for every 1°C of warming. This leads to longer dry spells and heavier, more dangerous deluges when rain finally falls. Scientists have linked climate change to heavy rainfall events such as the one that caused devastating floods last summer. Recently, Super Typhoon Bavi bore down on the Mariana Islands in the Western Pacific—the second super typhoon with extreme intensity to form there in a few months. Ocean warming also drives sea‑level rise through thermal expansion: as seas warm, they expand and push further up coastlines, amplifying storm damage.
The Role of El Niño
A “Super El Niño” on the Horizon
A new El Niño event is cycling through the Pacific, bringing even more extreme weather. Unlike typical El Niños, this year’s emerging pattern—dubbed a “super El Niño”—has an 81 percent chance of becoming one of the strongest in history, according to a recent National Oceanic and Atmospheric Administration forecast. El Niño churns up some of the ocean’s stored heat, bringing it to the surface where it interacts with the atmosphere and reshapes global weather.
Matthew England, a professor at the University of New South Wales, noted that global average temperatures will likely remain elevated into early next year. “The first year of an El Niño cycle tends to be on the warm side, but the records are generally broken in the second year,” he said. Alex Sen Gupta, also at the University of New South Wales, explained that El Niño years typically bring heavier rainfall to California and South America, and drier conditions to Australia and Southeast Asia. While El Niño tends to suppress hurricanes near the U.S., other regions see stronger cyclones with more rain.
There is no evidence yet that climate change is making El Niños or La Niñas stronger, but a hotter planet intensifies their effects. And some research suggests that the swings between strong El Niño and La Niña years are becoming more frequent, though scientists need more data to be certain.
A Deadly Health Issue Now
The oceans are sending their heat ashore, and the consequences are already deadly. From record‑breaking land temperatures to supercharged storms and sea‑level rise, the heat stored in the oceans is reshaping weather patterns worldwide. As Ruth Engel put it, this is not a future problem—it is here now.