[Puckster]

"discovery of an ozone hole."

Speaking of which......I remember an article concerning the majority of snow cover that melts and reconstitutes into snow again seasonally, in the arctic, that had an adverse chemical affect upon ozone. Couple this with and increased length of days in Alaska and that general region.....it seems that there is a connection.

[Ragnar54]

Longer warm seasons in the Northern Hemisphere correspond to longer cold seasons in the Southern half. Which seems to be consistent with:

"Further evidence that the Antarctic as a whole is in the midst of a cooling trend comes from the study of Watkins and Simmonds (2000), who analyzed region-wide changes in sea ice. Reporting on trends in a number of Southern Ocean sea ice parameters over the period 1987 to 1996, they found statistically significant increases in sea ice area and total sea ice extent, as well as an increase in sea ice season length since the 1990s. Combining these results with those from a previous study revealed these trends to be consistent back to at least 1978. And in another study of Antarctic sea ice extent, Yuan and Martinson (2000) report that the net trend in the mean Antarctic ice edge over the last 18 years has been an equatorward expansion of 0.011 degree of latitude per year. "

From:
New Antarctic study disputes CO2 Global warming link

Milankovitch theorized some effects of precession on climate. The summaries I have seen of his work emphasize solar angle and proximity. Do you know if he took the variation in the length of the warm seasons into account?