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Ocean Cools and Air Temps Follow

Ron Clutz, Science Matters

June Sea Surface Temperatures (SSTs) are now available, and we can see ocean temps dropping further after a short pause and resuming the downward trajectory from 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 June 2017.

In May despite a slight rise in the Tropics, declines in both hemispheres and globally caused SST cooling to resume after an upward bump in April.  Now in June a large spike upward in NH was overcome by an even larger drop in SH, now three months into a cooling phase. The Tropics also cooled off so the Global anomaly continued to decline.  Presently NH and SH are both changing strongly but in opposite directions.

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. Note that June 2017 matches closely to June 2015, with almost the same anomalies for NH, SH and Global.  The Tropics are lower now and trending down compared to an upward trend in 2015.

June satellite measures of air over the land and oceans also shows a sharp drop.  The graph below provides UAH vs.6 TLT (lower troposphere temps) confirming the general impression from SSTs.

In contrast with SST measurements, air temps in the TLT upticked in May with all areas participating in the rise of almost 0.2C.  Then in June SH dropped 0.4C, NH down 0.2C while the Tropics declined slightly. The end result has all areas back to March values except for the Tropics.  June 2017 compares closely with July 2015 but with no signs of an impending El Nino.

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.

USS Pearl Harbor deploys Global Drifter Buoys in Pacific Ocean

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.

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