1. There is a negative trend from 1854 to 2007 in the annual minimum NINO3.4 SST. All other SST and LST data sets I’ve checked so far have positive trends.
2. In the graphs of the temperature differences between NINO3.4 SST and hemispheric and global SST and in the graphs of the temperature differences between NINO3.4 and global LST and global combine surface temperature, there are underlying oscillations with a time span of approximately 80 years.
3. In recent years, there are also shorter time-span oscillations that mimic the solar cycle. These will now be discussed.
DO NINO3.4 SSTs MIMIC CHANGES IN TOTAL SOLAR IRRADIANCE?
In part 2 of this series, I noted the oscillation in the short-term graphs of NINO3.4 SST data. These oscillations appeared to have a frequency that mimicked that of the 11-year cycle of Total Solar Irradiance (TSI). Refer to Figure 1 & 2.
I’ve added monthly Sunspot data (I haven’t been able to find long-term monthly TSI data) and expanded the time frame for the comparative graphs, Figures 3 and 4. In both figures, the Sunspot data has been scaled with a multiplier of 0.015 and shifted by 25 to bring it close to the same range. I have made no other changes to the data in Figure 3. Referring to the last three cycles, there does appear to be a correlation, though the lag between Sunspot Number and NINO3.4 SST changes. Prior to then, the correlation evaporates through most solar cycles, periodically lining up again. In Figure 4, I’ve shifted the Sunspot data by 48 months to bring it into line with the NINO3.4 data, but the result is no better. I’ve also added volcanic aerosols, simulated by the Mean Optical Thickness data of the Sato Index, to see if there was any cause and effect there. No help.
Does this mean that NINO3.4 SSTs are not driven by solar irradiance? No. But, on the other hand, the possible correlation between the two data sets for the last three solar cycles does not prove that it is. It simply infers that there might be a link and that it’s something that needs to be investigated further. It could be that NINO3.4 SSTs are also influenced by other variables (very likely) and that the influence of these other variables changes with time (possible). Or it could also be that NINO3.4 SST is responding to changes in “apparent” solar irradiance of the surrounding Pacific Ocean, with “apparent” solar irradiance also taking into consideration the variations in solar irradiance reaching the ocean surface caused by volcanic eruptions, cloud cover, etc. Or it could be that there are different oceanic time lags that are reflected in the NINO3.4 SSTs. Or there might have been a change in SST sampling methods that impacted the earlier results, causing the correlation to be dampened. (NINO3.4 data before the opening of the Panama Canal in the 1910s have a much lower sampling number than after its opening, and there have been many recent papers about the effects of different sampling methods--insulated versus non-insulated buckets versus engine intake--on SST data.) Or it could be a combination of the above and other unnamed factors.
Sea Surface Temperature Data is Smith and Reynolds Extended Reconstructed SST (ERSST.v2) available through the NOAA National Operational Model Archive & Distribution System (NOMADS).
SATO Index Data is available at:
The Monthly Sunspot Data is available here: