Sea Surface Temperature
Sea-surface temperatures reached observed record highs in August.
Explanation
Sea-surface temperature (SST) is the temperature in the upper few metres of the ocean. It is measured by ships, buoys, and satellites. Because parts of the ocean close to the poles are ice covered for part of the year, SSTs are averaged across all ocean areas between 60°S and 60°N, an area which is largely ice free.
Methodology
The sea surface temperature datasets correspond to the ocean components of the nine datasets used in the assessment of global mean temperature. There are six independent sea-surface temperature datasets; ERSST is used in NOAAGlobalTemp and GISTEMP, and HadSST is used in HadCRUT5 and Berkeley Earth. In addition there is a dataset based on satellite sea surface temperature retrievals, ESA SST CCI v3.
The averages are calculated across ocean areas between 60°S and 60°N. This region excludes most areas that are covered by sea ice. Different datasets treat areas covered by sea ice differently, so a limiting the average to sea ice free areas allows for a more direct comparison.
To produce the plot, the following processing steps were performed:
- Calculated annual average from monthly averages using arithmetic mean
- Rebaselined to 1991-2020 by subtracting the arithemtic mean for that period from all data values.
- Selected years within the range 1850 to 2025.