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Thursday, September 27, 2012

Unforced Variations in Climate - Not Something to Dismiss

When is a Trend a Trend? When it is too late to do any good.  Nonlinear systems have their internal cycles and wanderings.  The wandering would have been "forced" since there is energy in these system they did not create.  When and how they use or lose energy totally depends on the dynamics of the systems.

The Lake Tanganyika surface temperature reconstruction by Tieney et al. has three interesting similar pseudo cycles.  The first, starting 16,500 years ago has two less data points than the third starting ~7000 years ago, and the data is coarse, but let's see how they compare.

I screwed my numbering up a little, Cycle 2 above actually is the first cycle starting around 16,000 years ago.  I picked the peak value as the start date and have all three on the same time scale.  The average is there just for reference, complex cycles would never have a reliable average, but a range that may be useful.

All three of the pseudo cycles in the reconstruction have a rough period 4300 hundred years with irregular dampened oscillations with periods of roughly 1135 to 1350 years.  The Bond cycles or events are irregular North Atlantic climate cycles of 1470+/- 500 years associated possibly with DansgaardOeschger events or by my estimation, just decay curves for ocean perturbations.  Note that near in the 600 to 1250 year end of the ~4300 year cycles above, there is an average warming of approximately 0.75C degrees.  In the blue Cycle one, the increase was about 1.0 C degrees from ~1200 to ~1000 years in the pseudo cycle or about 0.5C per century due to apparently Unforced Variations.  Nasty term that, Unforced Variations.

Lake Tangayika is not in the North Atlantic, it is just south of the Equator on the Eastern Side of Africa nearer to the India Ocean.  Imagine that, the Indian Ocean appears to have irregular Unforced Variability.  

So then next time someone mentions that Unforced Variations zero out and therefore do not impact climate, laugh your butt off.  

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