More on the AO

If you’re researching the Arctic Oscillation, you’re bound to come upon this site: http://jisao.washington.edu/ao/.

The first graphic presented on the website is the one I posted in my previous post. 

Along with it, the description: “Fluctuations in the AO can be seen in the time series of SLP anomalies for the North Pole”.  SLP stands for sea level pressure.  The paper referenced for the graph is listed as “Hodges, G., 2000. The new cold war. Stalking arctic climate change by submarine. National Geographic, March, 30-41.”  Athough I could not gain access to the article, the abstract reads, “In an attempt to better understand changing climate conditions in the Arctic, where water temperatures are rising and ice cover is both thinning and receding, the American navy has made nuclear submarines available to scientists to help them conduct their research in this inhospitable and remote environment.”  I’ve never seen data (or in this case “screw the data, we’re makin’ a graph!”) taken from a National Geographic article, and I am very suspicious.

The graph appears to show a steep trend towards lower-than-normal SLP over the past few decades.  Before then, there doesn’t appear to be much variance.  (In fact, if you look closely, you can see MBH98 with the Medieval Warm Period just below “normal” in the 1920s and with the mid-century global cooling scare in the middle of the 1990s.)  No comment is made about why the Arctic Oscillation looks more like a hockey stick than an oscillation.  The intention of the original author was to illustrate the effect of climate change on the Arctic, and perhaps that was also the intention of its use on the site. 

Alone, this situation of using a graph from a National Geographic article, implying that the Arctic Oscillation is being significantly altered by climate change without ever directly stating it, would be confusing.  But once you throw in the fact that the site then provides monthly data from David Thompson that does not seem to match up to the Hodges 2000 data, things get fishy.  Why did they show Hodges data, but not Thompson’s?  Thompson’s data, graphed both with monthly anomolies and yearly averages, is shown below:

Less impressive, right?  The link to Thompson’s website is broken, but I found it here.  And the data supplied by the JISAO site should exist somewhere in here.

So, I have a few questions.

Why is Hodge’s data being used at all?  National Geographic?  How was it smoothed?  Why do they use his graph, without access to his data or his ascetic massaging of the data, when they have the raw data of Thompson on the same website?  Why did they decide to use Hodge’s data over Thompson’s data?  Should they not have provided an explanation or used both?

I doubt it’s intentional manipulation to prove a point; it’s just reflective of an attitude indifferent to accuracy.

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One Response to “More on the AO”

  1. Charles Colenaty Says:

    This is a correction to my comment of a few minutes ago. I rechecked the graph and discovered that it really does start at 1900. And in revisiting the climate bloggers list I discovered that Wattsupetc and Lucia were already there. I guess that this just isn’t my day.

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