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Long Term Auto Correlation

Notes:

In this plot, the evenly spaced correlation peaks every 41K years, consistent across a wide range of smoothing intervals, are an unambiguous marker for a 41K year periodic effect. Furthermore, 41K year smoothing makes this effect completely disappear. The modulation of these peaks indicates that longer periodic effects are superimposed on top of the 41K year periodic effect as are harmonics of the 22K effects. The later can be removed by 22K year smoothing.

The period over which the Earths obliquity (tilt) varies is 41K years. It varies between 22.1 and 24.5 degrees, is currently close to it's midpoint (23.4 degrees), is decreasing, and will reach it's minimum in another 8K years. It reached it's last maximum about 13K years ago, which is seen as a global temperature dip as the Earth came out of the last ice age. We can continue to expect a warming climate until this reverses in about 8K years, however the 22K influence will start to reverse soon, and will tend to offset most of this effect.