Ice core temperature history

Source (ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/deutnat.txt)

Possible Trendlines

• The earth spends more of its time being cold then warm.
• Temperatures appear to alternate between rapid rising or rapid declining patterns.
• Rates of change appear to be consistent and constant (trend lines are mostly linear and parallel).
• Trends abruptly change direction.

Possible upper and lower limits?

• Trends going into Ice Age seems to be somewhat bounded to a 'channel' with declining upper and lower limits.
• Coming out of an Ice Age occurs rapidly and uninterrupted;
• There appears to be striking self-similarity (smaller sub-structures look similar to larger structures).
• Overall the structure appears to have a strong fractal nature with 'saw-tooths' inside of 'sawtooths'.

Saw Tooth Structure

What could possibly explain this structure? It seems likely that:

• Periodic nature of ice-ages probably means Milankovitch orbital forcing is what triggers ice-age changes.
• Positive feedback dominates ice-age changes in order to drive temperatures in such a rapid and linear way.
• Discontinous inflection points and occasional flat top may mean positive feedback drives system to saturation.