Data: John Abraham, University of St. Thomas; Chart: Axios Visuals
Last year broke a record for the most heat content present in the upper 2,000 meters (6,562 feet) of the oceans.
Why it matters: The oceans absorb about 90% of the extra heat in the Earth system trapped by greenhouse gases, making the metric a striking indicator of human-caused global warming.
By the numbers: The five highest values of annual ocean heat content have come in the past five years, according to NOAA.
The big picture: "If you want to know how fast and how far global warming is going to go, the answer is in the oceans," study coauthor John Abraham told Axios.
Sea surface temperatures were also off the charts in 2023, which helped drive extreme weather on land, too. However, surface temperatures are only a small part of the heating that took place in deeper waters, Abraham said.
Parts of every ocean had record warm sea surface temperatures, particularly in the North Atlantic and equatorial tropical Pacific.
The bottom line: According to the temperature tracking group Berkeley Earth, "[n]o places on Earth experienced a record or near-record cold annual average" in 2023.