Dienstag, Januar 08, 2008

The eternal return of the same...not.

One of the blogs I occasionally read is Global Warming Politics from Philip Stott. You can find it here.

In this post he points out, or rather points to a scholarly work that points it out, that there are problems with statistics used by environmentalists.

In this case, there have been revisions to the data such that a supposed deforestation trend appears and then after a revision disappears, repeating itself at every revision, and has been since the 1970s.

But this statistic continues to be quoted and then extrapolated to show that massive deforestation is our future.

Let me quote him:

Dr Grainger first examined data published every 10 years by the United Nations Food and Agriculture Organization (FAO) since 1980. These cover all forest in the humid and dry tropics and appear to indicate decline. FAO's Global Forest Resources Assessment 2000, for example, showed that all tropical forest area fell from 1,926 million hectares to 1,799 million hectares between 1990 and 2000. Ten years earlier, however, FAO's previous report said that tropical forest area fell from 1,910 million ha to 1,756 million ha for the same 90 countries between 1980 and 1990. 'Owing to corrections to the earlier study, the 1990s' trend was just like a 're-run' of that in the 1980s,' said Dr Grainger. 'The errors involved in making estimates for forest area could easily be of the same order as the forest area reported cleared in the previous 10 years.'


That last says it all: the errors are of the same magnitude as the deforestation process.

What does that tell us?

That such statistics are fundamentally useless.

If the error rate for a time series is so large that it makes any movement of the time series meaningless - say a rate change of 5% when the error rate is 10% - then any analysis based on that time series has just been discounted to nothing: you simply cannot make any judgment about cause and effect, of trends, of correlation, if that which you are observing is smaller than the average error rate.

The title of this post comes from Nietzsche: the eternal return in his philosophy is the ultimate affirmation of living, to accept the idea - terrifying that it is to him - that your life will constantly recycle, not merely with the joy and happiness, but also the worries, pains and despairs, the embarrassments and horrifying moments. While Nietzsche finds it frightening, to accept life this way is to place high marks on being alive, of accepting degradation and shame in order to continue to live (what one can draw out of that for pacificism is another story entirely...).

But the eternal return to faulty statistics, to incorrect conclusions and misled judgements: that is not something to be desired.

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