Digital Diatribes

A presentation of data on climate and other stuff

Antarctic Oscillation

Posted by The Diatribe Guy on September 21, 2009

I thought I’d start taking a look at the different Oceanic Oscillations to see if there’s anything at all I can glean from the data.

The first set of data is the AAO Index data which goes back to 1979 here. This could be a mistake, but I pulled in data from this source for the pre-1979 numbers. The reason I say it could be a mistake is because the latter source’s numbers do not match all that well to the former’s. This puts the pre-1979 data in question as it relates to the newer data. And, as the chart results came into view, I think we see that splicing this data probably does more harm than good. With that said, I have kept it in for this view of the data, but may choose to eliminate it in future reviews.

We’ll start here with the raw data, and a fitted line that I will explain:

antarctic_oscillation_200908_raw

Antarctic Oscillation Data as of 200908

The current anomaly value is -0.686, which is the fourth consecutive negative anomaly. Previously, there were 11 consecutive positive anomalies.

The line on the chart isn’t actually a linear fit, though it is very close. It is actually a best-fit sine wave. However, there are no short-term waves evident in the data, so the best-fit wave is a long-term wave that completes a 360-degree phase over 12,000 years. Obviously, trying to make a strong case for a 12,000 year cycle is a bit silly based on 60 years of data. Nevertheless, it’s interesting to consider that the earth’s precession of the poles moves along this approximate time period. It’s also worth noting that this same approach on the Arctic Oscillation yielded a sine wave of 9500 years. I make no assertions as to the accuracy of this, I just find it a point of interesting congruence.

So, with a 12,000 year fitted wave, the 60 years essentially has a linear fit associated with it. In the chart, it is clearly an upward trend. However, observe the differene between the pre-1979 and post-1979 areas of the chart.

Two things are apparent: (1) the volatility in the anomaly values is much higher prior to 1979, and (2) the upward trend occurs in the pre-1979 data.

Putting numbers to these observations:
1) The Standard Deviation of observations for the data prior to 1979 is 1.749. The standard deviation for 1979 – current is 0.988. The average positive anomaly prior to 1979 is 0.960. The average positive anomaly 1979-current = 0.746. The average negative anomaly pre-1979 is -1.778. The average negative anomaly for 1979-current is -0.830.

2) The slope from 1948 – 1978 represents warming of 5.26 degrees Celsius per Century. The slope from 1979 – current represents 0.68 degrees warming per Century.

It seems pretty clear that the data prior to 1979 is a different animal than post-1979.

All in all, there just doesn’t seem to be a whole lot of anything here to discuss about the Antarctic Oscillation being a driver of warmer and cooler cycles. If anything, the general consistencey of the index over the last 30 years would act as a stabilizer of temperatures over the long haul. Now, it may be that there are immediate impacts in the very short term with regard to some of these fluctuations – especially in times of some persistence in positive/negative anomalies. A correlation analysis woould ahve to be done to see if this would affect short-term temperatures, or whether or not the temperature is affective the short-term index reading.

A couple other charts are presented here simply because I put them together, but there is probably not a lot to be learned from them. They smooth the data, and generally show the upward trend discussed. above, as artificial as it may be for the last 30 years.

antarctic_oscillation_200908_12

Antarctic Oscillation Data as of 200908 - 12 month Smoothing

antarctic_oscillation_200908_60

Antarctic Oscillation Data as of 200908 - 5 Year Smoothing

antarctic_oscillation_200908_120

Antarctic Oscillation Data as of 200908 - 10 Year Smoothing

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One Response to “Antarctic Oscillation”

  1. [...] Antarctic Oscillation [...]

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