May Sea Surface Temperatures (SSTs) are now available, and we can see ocean cooling resuming after a short pause from the downward trajectory during the previous 12 months.
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.
The chart below shows the last two years of SST monthly anomalies as reported in HadSST3 including May 2017.
After an upward bump in April 2017 due to the Tropics and NH, the May SSTs show the average declining slightly. Note the Tropics recorded a rise, but not enough to offset declines in both hemispheres and globally. SH is now two months into a cooling phase. The present readings compare closely with April 2015, but currently with no indication of an El Nino event any time soon.
Note that higher temps in 2015 and 2016 were first of all due to a sharp rise in Tropical SST, beginning in March 2015, peaking in January 2016, and steadily declining back to its beginning level. Secondly, the Northern Hemisphere added two bumps on the shoulders of Tropical warming, with peaks in August of each year. Also, note that the global release of heat was not dramatic, due to the Southern Hemisphere offsetting the Northern one.
Satellite measures of the air over the oceans give a slightly different result. The graph below provides UAH vs.6 TLT (lower troposphere temps) over the oceans confirming the general impression from SSTs.
In contrast with SST measurements, air temps in the TLT over the oceans upticked in May with all areas participating in the rise of almost 0.2C. In the satellite dataset, it is quite noticeable that land air temps rose quite strongly and may have caused air temps in the May TLT over oceans to show higher anomalies than the SSTs.
We have seen lots of claims about the temperature records for 2016 and 2015 proving dangerous man made warming. At least one senator stated that in a confirmation hearing. Yet HadSST3 data for the last two years show how obvious is the ocean’s governing of global average temperatures.
The best context for understanding these two years 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 these years.