Ocean Heat Content
Ocean heat content reached an observed record high in 2025
Explanation
Ocean heat content (OHC) is a measure of the amount of heat stored in the ocean, estimated by integrating ocean temperatures from the surface to a depth of 2 000 m. Ocean temperatures are measured by research ships, expendable instruments deployed from ships. Since around 2005, these have been supplemented by measurements from autonomous Argo floats that provide near-global coverage down to 2 000 m. The ocean absorbs around 90% of the excess energy accumulating in the Earth system.
Methodology
This indicator is based on temperature measurements in the upper 2000 m of the ocean obtained from in situ observations, including from the Argo profiling float network and earlier ship- and buoy-based measurements. Note that global ocean heat content values are given for the ocean surface area between 60°S and 60°N and limited to areas deeper than 300 m. A baseline of 2005–2025 is used for the ocean heat content time series as near-global coverage is available for this period thanks to the network of Argo subsurface floats.
To produce the plot, the following processing steps were performed:
- Calculated annual average from monthly averages using arithmetic mean
- Rebaselined to 2005-2025 by subtracting the arithmetic mean for that period from all data values.
- Selected years within the range 1960 to 2025.