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DomeC 15K years + smoothing

Notes:

Applying 1500 year smoothing to the DomeC data produces approximately the same results as for the Vostok data. Overall, the DomeC temperature and gas concentrations are more consistently aligned with each other.

The temperature minimums at 8K and 13K years, correspond exactly to Earth orbit and axis periodicity. About 8K years ago, perihelion (shortest Earth-Sun distance) was in early to mid May, which is when the Northern hemisphere is most reflective from the accumulation of winter snow. About 13K years ago, the Earth's tilt was at it's maximum, corresponding to maximum seasonal variability, more snow coverage and more reflectivity. In both cases, the additional reflected energy resulted in lower average global temperatures.

As the Earth's tilt has been decreasing and perihelion has been shifting to the Southern hemisphere summer, these effects have more or less cancelled, contributing to the relatively stable climate over the last several thousand years.