Extended Reconstructed Sea Surface Temperature Version 4

Graph comparison of global annually averaged sea surface temperature anomalies in versions 4 and 3b of the ERSST dataset

This graph compares global annually averaged sea surface temperature anomalies in versions 4 and 3b of the ERSST dataset.

We’re announcing the release of version 4 of the Extended Reconstructed Sea Surface Temperature (ERSST v4) dataset, a global monthly sea surface temperature analysis derived from the International Comprehensive Ocean–Atmosphere Dataset and its near-real-time stream from the Global Telecommunications System. This new version contains several enhancements over the previous version (version 3b), which has been in operation since 2008. Greater coverage in high-latitude ice-free oceans, updated sea ice data, and improved ship bias corrections are among the many enhancements the new dataset provides.

One of the most significant improvements involves corrections to account for the rapid increase in the number of ocean buoys in the mid-1970s. Prior to that, ships took most sea surface temperature observations. Several studies have examined the differences between buoy- and ship-based data, noting that buoy measurements are systematically cooler than ship measurements of sea surface temperature. This is particularly important because both observing systems now sample much of the sea surface, and surface-drifting and moored buoys have increased the overall global coverage of observations by up to 15%. In ERSST v4, a new correction accounts for ship-buoy differences thereby compensating for the cool bias to make them compatible with historical ship observations.

The new version of ERSST shows the same trend in sea surface temperature as previous versions—an increase in the global average of 0.005°C per decade since 1880. However, the changes in the new version, including the adjustments to account for more buoys, did result in a higher trend in global ocean temperature since 2000. In ERSST v4, the rate of increase in global ocean temperature is 0.099°C per decade, while it was 0.036°C per decade with the previous version.

With this release, ERSST v4 has become the operational sea surface temperature component of NCEI’s recently updated global surface temperature analysis known as NOAAGlobalTemp. In this new version of NOAAGlobalTemp, the trend in global land and ocean surface temperature since 1880 is 0.066°C per decade. There is little change in annual global surface temperature rankings for the top 10 warmest years on record, with 2014 remaining the warmest year. The trend from 2000 to 2014 in the latest version of NOAAGlobalTemp is 0.112°C per decade, compared to 0.066°C per decade in the previous version of the dataset.

To learn more about ERSST v4, check out these two articles published in the Journal of Climate:

Check out the ERSST v4 web page on June 18 for the latest global data for May 2015.