The best context for understanding decadal temperature changes comes from the world’s sea surface temperatures (SST), for several reasons:
- The ocean covers 71% of the globe and drives average temperatures;
- SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
- A major El Nino was the dominant climate feature in recent years.
HadSST is generally regarded as the best of the global SST data sets, and so the temperature story here comes from that source, the latest version being HadSST3. More on what distinguishes HadSST3 from other SST products at the end.
The Current Context
The cool 2020 Spring was not just your local experience, it’s the result of Earth’s ocean cooling off after last summer’s warming in the Northern Hemisphere. The chart below shows SST monthly anomalies as reported in HadSST3 starting in 2015 through June 2020.
A global cooling pattern…
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