Forum Sophomore
Joined: 10 Aug 2007
Posts: 128
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We're experiencing a bit of a cold spell now, which is hard to attribute to greenhouse effect. So, it's probably La Nina like the big warm spike of 1998 was attributed to a strong El Nino. Sure enough the alarmists recognise this but it seems that an occasional spike up or down does not a trend make.
Let's see about that and let's plot the EL Nino Southerly Oscilation (ENSO) index againt the HADCRUT3T surface temperatures of the last 50 years in monthly increments, then we get this:
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Indeed the ENSO index does not show a trend and a correlation squared (R2) of 13% (in the X-Y scatter plot on top) is not very overwhelming.
But wasn't there something with a delay? The global temperatures reacting a bit slower on the ENSO activity? What, if we did not only look at the immediate correlation but also at the cumulative effect of the previous months? So we add the previous value of the ENSO index to the next month and we get this:
Click on the image to view it at its original size
Hmmm, The correlation squared drops even one percent but we also see a trend now, especially after 1975, nicely matching the trend of HADCRUT3 global temperatures. Are we getting somewhere?
Actually by adding the complete former trend we weight older months just as heavy as the last month. That can't be quite correct but if we multiply the accumulated ENSO index with a factor a little smaller than one, then the effect of the older months diminish gradually
So let's try a factor 0.995:
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Now look at the r2: 53% !
Also notice the trends of the accumulated ENSO, coming down from 1950 to 1975 then up again to about 1998 and then reversing again. Where could that long term memory effect of the ENSO come from?
is it the Pacific Decadal Oscilation?
Click on the image to view it at its original size
It certainly appears that the cumulative effect of the ENSO index, appears to be the PDO and for a large part responsible for the general trends. This of course leaves less and less trend to be explained by enhanced greenhouse effect. |
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