The Milankovitch Groove

In a core, the parameters of our orbit.
See the cycles: one, two, three,
As they add and subtract from each other,
In their varying frequencies.

The quickest of these is precession,
Just 20ka* here,
As the earth, a-wobble on its axis,
Sets the solstices forward in the year.

And then the obliquity cycle,
Tilts us forward and away from the sun.
That 41,000 year period,
Once governed when glacials were done.

Eccentricity reigns from mid-Pleistocene:
100,000 year orbital queen.
Is our orbit more or less circular?
That's what rules our climatic regime.

These cycles together can tell us,
How much light there is reaching our earth.
Though it varies but just five percent,
There's a massive effect on our turf.

For our climate, indeed, it is complex,
Insolation sets feedbacks a-rife,
That affect not just air and the ocean,
But the weather, the bugs and the ice.

And all that such proxies do tell us,
Might vary, but still there's one tune,
For all of the earth, it is dancing,
To the constant Milankovitch groove.

* This number I've given is rounded,
The figure I usually see,
Is 19-23,000 -
Who knows why the uncertainty?

 

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