The earth just lived through its hottest month on record—but if we didn’t have the power of the oceans on our side, things could have been even more catastrophic. Since the 1970s, the world’s oceans have absorbed 93 percent of the excess heat in the atmosphere generated by burning fossil fuels and about one-third of the carbon dioxide emissions released into the atmosphere.
Regina Rodrigues, a professor of physical oceanography and climate at the Federal University of Santa Catarina in Florianópolis, Brazil, specializes in marine heat waves. Oceans, she told me, act as a buffer against the most extreme heat for those of us on land.
“If the ocean wasn’t absorbing this excess heat, we would be in a much worse situation,” Rodrigues said. “It’s great for us, but all of this comes at a price.” That price is a steady increase in sea surface temperatures: The world’s oceans have warmed by around 0.13 degrees Celsius (0.23 degrees Fahrenheit) per decade over the past 100 years.
The unbelievable temperatures recorded in waters across the world this summer aren’t all thanks to climate change. The El Niño effect is also helping to heat the tropical North Atlantic, Rodrigues said, and could be impacting the jet stream, which is triggering heat waves around the Florida area. “There’s several different things all happening in the same spot at the same time,” she said. “That’s maybe why we’re getting these real extremes.”
All this ocean warming has real impacts for life on land. Warmer waters accelerate the melting of the world’s glaciers and sea ice, supercharging the rate of sea level rise. Many of the corals that are struggling to survive act as important natural barriers for coastlines, protecting them from storms and floods. Hotter waters can decrease oxygen and key nutrients in the ocean and change the balance of ecosystems, seriously impacting larger species we rely on for food.
We could also be in for some monster storms this year. Warmer sea surface temperatures give hurricanes more ammunition to strengthen before they hit land; warmer air also allows more moisture to form, juicing up these storms. These extreme ocean temperatures are coming right as the Atlantic’s hurricane season hits its peak. “Maybe the El Niño will counteract that, but if it doesn’t, we could have a very busy hurricane season,” Rodrigues said.
In the longer term, the overheating ocean could change weather patterns around the globe. Scientists have long been worried about the functioning of a key ocean current known as the Atlantic Meridional Overturning Circulation in a warming world. The AMOC, which moves warmer water around the Atlantic Ocean, is already slowing down, thanks at least in part to climate change. A study released late last month predicted that, in an absolute worst-case scenario, the AMOC could collapse in as little as two years. While we simply don’t know when—or if—the AMOC will collapse or what exactly may happen when it does, the results could be enormous shifts in worldwide temperatures and precipitation—potentially catastrophic changes.
I asked Rodrigues how she was feeling about all this. Even for those of us who cover the climate crisis regularly, that 100-degree-plus reading in Florida was truly shocking—was she feeling that way too?
“It’s not that we didn’t know extremes would happen, but … what’s more surprising is that they’re coming faster than what we previously projected in models,” she told me. “When scientists say this is ‘shocking’—we knew this would happen, but the difference is that we thought it would be a little bit later, not so quick. But these extreme events are coming really hard, and really quick.”
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