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Monday, May 12, 2008


Please refer to the notes on data source prior to downloading the JunkScience .csv files.


In Part 1 of this series, the magnitude of the variations in Land Surface Temperature (LST) overwhelmed Sea Surface Temperature (SST), making SST appear almost flat. Figure 2.1 provides a detailed view of the annual global SST span and the changes in its maximum and minimum values.

Figure 2.1: NCDC Absolute Global Temperature – Ocean – Jan 1900 to Mar 2008

Pulling the mass of data from the middle, Figure 2.2 illustrates the maximum, minimum, and average readings of each calendar year from 1880 to 2007. Figures 2.3 through 2.5 provide a better view of the individual data and their linear trends.

Figure 2.2: NCDC Absolute Annual Global SST – Maximum, Minimum, Average – 1880 to 2007

Figure 2.3: NCDC Absolute Annual Global SST – Average – 1880 to 2007

Figure 2.4: NCDC Absolute Annual Global SST – Maximum – 1880 to 2007

Figure 2.5: NCDC Absolute Annual Global SST – Minimum – 1880 to 2007

The next graph was a surprise to me. The difference between global SST annual extremes (maximum minus minimum) increased over time. Refer to Figure 2.6. This indicates that maximum annual global SST grew faster than minimum, which is the opposite of the combined and, logically, the LST trends. (In order for the annual global combined temperature difference between extremes to be decreasing, then that decrease, logically, has to come from LST, and that decrease in LST extremes has to be greater than the increase in SST extremes.)

Figure 2.6: NCDC Absolute Annual Global SST – Maximum minus Minimum – 1880 to 2007

Note the 50- to 60-year oscillation in the curve compared to the linear trend line. It will be easier to see with a polynomial trend. Refer to Figure 2.6b.

Figure 2.6b: NCDC Absolute Annual Global SST – Maximum minus Minimum – 1880 to 2007

Adding raw Atlantic Multidecadal Oscillation (AMO) data for comparison, though it has been shifted 0.5 deg C, Figure 2.7, the magnitude of the AMO oscillations (red data) suppress the global SST data (blue).

Figure 2.7: NCDC Absolute Annual Global SST – Maximum minus Minimum vs AMO – 1880 to 2007

Assume that the surface area of the Atlantic Ocean is approximately 30% of the global ocean area and that the North Atlantic represents 50% of the Atlantic. Multiply the AMO data by 15%, then add 0.7 deg C to shift the range, and the correlation becomes apparent. See Figure 2.7b.

Figure 2.7b: NCDC Absolute Annual Global SST – Maximum minus Minimum (Blue) vs AMO (Red) – 1880 to 2007 – AMO Scaled and Ranged

Just in case you’ve never seen it, Figure 2.8 is a comparison of global average SST with the AMO.

Figure 2.8: NCDC Absolute Annual Global SST – Average vs AMO – 1880 to 2007

To put the relationship of AMO and Global SST into perspective: In Figure 2.9 NCDC, the AMO is extracted from the average annual global SST, using the 15% factor discussed above.

The impact on global SST is minimal, BUT…

Figure 2.9 NCDC: Absolute Global SST – Annual Average vs Annual Average with AMO Removed – 1880 to 2007

Now recall the effect of the AMO on Northern Hemisphere LST. From the RealClimate Glossary, “This pattern is believed to describe some of the observed early 20th century (1920s-1930s) high-latitude Northern Hemisphere warming and SOME, BUT NOT ALL (my caps), of the high-latitude warming observed in the late 20th century.”

In the next post in the series, I’ll visit NCDC Absolute Land Surface Temperature.

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