Heat trapped by greenhouse gases is raising ocean temperatures faster than previously thought, concluded an analysis of four recent ocean heating observations.
The results provide further evidence that earlier claims of a slowdown or "hiatus" in global warming over the past 15 years were unfounded.
"If you want to see where global warming is happening, look in our oceans," said Zeke Hausfather, co-author of the paper. "Ocean heating is a very important indicator of climate change, and we have robust evidence that it is warming more rapidly than we thought."
Ocean heating is critical marker of climate change because an estimated 93 percent of the excess solar energy trapped by greenhouse gases accumulates in the world's oceans. And, unlike surface temperatures, ocean temperatures are not affected by year-to-year variations caused by climate events like El Nino or volcanic eruptions.
The new analysis shows that trends in ocean heat content match those predicted by leading climate change models, and that overall ocean warming is accelerating.
"While 2018 will be the fourth warmest year on record on the surface, it will most certainly be the warmest year on record in the oceans, as was 2017 and 2016 before that," Hausfather said. "The global warming signal is a lot easier to detect if it is changing in the oceans than on the surface."
The four studies, published between 2014 and 2017, provide better estimates of past trends in ocean heat content by correcting for discrepancies between different types of ocean temperature measurements and by better accounting for gaps in measurements over time or location.