Jun 18 2007
Southern Oscillation Index and Global Temperatures Redux
In my climate science refresher series, I reproduced a temperature and SOI graph in an attempt to show that El Nino does not cause global warming. When I made the graph, I used a 20-year filter of the data instead of a shorter time period, which smoothed out the effects of shorter time period events. Since El Nino has a period of about 7-10 years, and the climatic effects of volcanoes last about 2 years, both of these were essentially eliminated from my plots. I have replotted the now monthly-averaged data instead of the previous yearly-averaged data seen below.
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As can be seen, I have added vertical lines indicating the approximate times of major volcanic eruptions.
| Volcano | Location | Year | Color |
|---|---|---|---|
| Taal | Philippines | 1911 | Red |
| Lamington | Papua New Guinea | 1951 | Purple |
| Hibok Hibok | Philippines | 1951 | Purple |
| Agung | Indonesia | 1963 | Green |
| St. Helens | United States | 1980 | Orange |
| El Chichón | Mexico | 1982 | Orange |
| Pinatubo | Luzon, Philippines | 1991 | Pink |
There is still a small anti-correlation between SOI and the global temperature, but it is less than when I used the 20-year average. This tells me that the largest correlations between SOI and global temperatures do not occur on the 2-year to 20-year time scale. Neither are they shorter than 2 years - both smoothing techniques removed the highest frequency variations. It would be interesting to see at which frequency they have the highest correlations. I have a script to do that, but thought I could stretch out another post with that figure.
After most of the eruptions, there is a decrease in the global temperature caused by the release of aerosols into the stratosphere. These reflect more sunlight and thus tend to cool the surface. I’ll look more closely into this in a future post. Stay tuned.
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[...] I’m too lazy to reproduce a globally-averaged temperature plot, but luckily for you, I already did one (with something else on it too) in a previous post. [...]