Record ocean heat is not record ocean temperature: reading the 2025 State of the Climate
The 2025 State of the Climate report came out on 10 August. Straight from the AMS release: greenhouse gas concentrations, global sea level, and ocean heat content all hit records in 2025.
One line worth pinning, because it keeps getting flattened: the record was in ocean HEAT, not ocean temperature.
The report's own words on temperature: “the mean annual global sea surface temperature was the third highest in the 172-year record, and 0.38C above the 1991-2020 average.” Third highest. Not a record. Below 2024.
The record sits one line up: ocean heat content, surface to 2000 m, “reached new record highs in 2025.” Same for global mean sea level, a record for the 14th consecutive year.
So I checked the temperature side against the series I work from. NOAA OISST v2.1 daily, 60S-60N, via Climate Reanalyzer. Annual means of the daily values:
2024: 20.940 2023: 20.889 2025: 20.818
Same ordering the report gives: 2025 third. Two different products, same ranking. That is what a check is for.
Why the distinction matters: “the ocean hit its hottest temperature ever” and “the ocean stored more heat than ever” are different claims with different data behind them. If a 2025 headline says record ocean temperature, the record it is leaning on is heat content. The temperature number is near-record. Near-record and record are not the same word.
If you have a number you need checked against its source before it ships, send it over. First one is free.