Clarification on weather statistics

Thu, May 31, 2012, 01:00

A misleading headline related to weather statistics is causing a bit of traffic on Twitter and I want to clarify the issue.

We have altered the headline online to better reflect what the article is trying to say.

The weather stats released by Met Éireann are 30 year means. They allow the forecasters to put daily weather in some kind of context: it is warmer than usual, there was more sunshine this month than the average, this was the coldest May since etc, etc.

These 30 year means are not capable of telling us anything new about global warming one way or the other. They were not designed to do so and in any case would be a tiny data set upon which to make any extravagant claims.

The one thing you can take from these 30 year averages is that the newer data set shows that on average temperatures are now higher when compared to the previous data set.

Met Éireann head of forecasting Gerald Fleming does however have something useful to say about this increase, which depending on how you look at the stats is between 0.5 degrees C and 0.75 degrees C.

If average world temperatures rise by three to six degrees C by the end of the century, then the increase seen in the Irish 30 year means matches up very well with the 3-6 degree projected temperature increase.

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