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Friday, October 5, 2012

Just for Fun - Climate Shifts

There is the typical blog arguments going on about what caused what, if it's warming, if it's cooling blah, blah, blah.  A complex dynamic system does all sorts of weird stuff, just to make people look silly.  There is no "true" solution, but there are a few hints about what caused what.  Change point analysis is a good way to get some hints.  So here is a little step by step application of Captain Dallas' Kmart change point analysis procedure.

This is the GISS land and ocean regional plots for the northern extratropics 24N-90N, the Tropics 24S-24N and the southern extratropics.  A nice messy chart of the Anomalie with linear regressions showing that the tropics are warming least and the northern extratropics are warming the most.  Make a note of the rates of warming, 0.004, 0.006 and what should be 0.008 which would be degrees C per year.

The next two will be a little boring, but hang in there.

This is the same data detrended.  Since I did not average, you can see how they stack.

Here I just adjusted the detrended data to a common baseline.  It is still pretty much a noisy mess right?

Now this is the Kmart analysis.  All it is is sequential linear regressions of each data set (11 years in this case).  Change point show as peaks a valleys.  Nothing Earth shattering.  Now notice the arrows.  There are three similar peaks at different times.

Now by shifting the Southern Extratropics forward by 9 years and the Northern Extratropics back by 18 years you can see a little about what to expect in a semi-chaotic system.  The southern extratropics had an "event" around 1960, on this shift time line.  Nine years later, the tropics had an "event", the 18 years later the northern extratropics had an "event much like the tropics.  All three had responses to the "events" of roughly the same period, then there is a new change point or climate shift.  The "cause" of the initial change point is likely the Super Duper La Nina.

So should you be inclined to wager on long term weather, there appears to be a cooling trend in our near future.  Since the Northern Extratropics tend to overshoot change points both in amplitude and time lag, the cooling could be about 0.3 C degrees.  However, it is a semi-chaotic system, so things can change at any time, though it is rather unlikely there will be a major warming forcing in the next decade or two.

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