“We want to stress that global warming is actually ocean warming, and ocean warming has serious consequences,” said Lijing Cheng, lead author on the report and climate and environmental science professor with the Institute of Atmospheric Physics at the Chinese Academy of Sciences. “Ocean warming keeps breaking records, which is a reminder that the world needs action to combat climate change.”
Ocean heat is a better indicator of the climate crisis than air temperature because natural cycles like La Niña and El Niño play a “relatively small” role in ocean warming, according to Kevin Trenberth, an author on the report and scientist at the National Center for Atmospheric Research in Colorado. And last year was a record even despite La Niña conditions in the Pacific Ocean — a cooler-than-average temperature pattern in the ocean around the equator.
“The impacts are perhaps subtle but profound,” Trenberth told CNN. “To stop this [trend], we really need to get to net-zero [emissions], and many countries have plans but not enough actions to support those. In the meantime, we must prepare better and build resilience.”
The far-reaching impact of warmer oceans
“Warm ocean provides fuel to storms, so ocean warming will naturally support stronger and longer-lasting storms,” Cheng said.
“Ocean warming — aside from causing coral bleaching and threatening sea life and fish populations that we rely upon for roughly 25% of our protein intake globally — is destabilizing Antarctic ice shelves and threatens massive meters of sea level rise if we don’t act,” Michael E. Mann, a climate scientist at Pennsylvania State University and one of the authors of the study, told CNN. “So this finding really underscores the urgency of climate action now.”
Cheng said part of the reason action is so urgently needed is because the oceans will continue warming for decades after fossil fuel emissions are slashed.
“Many countries have set goals to become carbon neutral around the middle of this century,” he said. But “ocean warming will continue after 2060 and sea level will keep rising.”
Trenberth explained that although reaching net-zero emissions would end Earth’s energy imbalance, “the oceans are slow to respond.” Heat will continue to “percolate to greater depths; sea level keeps rising for a lot longer,” he said.
Even if countries make good on their pledges to reduce emissions soon, researchers say further ocean warming will continue and communities must prepare for the far-reaching consequences. The report’s authors noted that the long-term risks that come with warming oceans — including sea level rise and more frequent flooding — should be accounted for in “engineering design, building codes, and modifications to coastal development plans.”