Just another thinking out loud post gang. I have been puzzling over what natural feedback to high SST could help trigger a return to a glacial period. There is no particular reason other than once it get hot, it starts to get cold. That is not particularly enlightening.
In the northern hemisphere it is pretty easy to imagine that a warmer world with an ice free summer Arctic Ocean would produce more precipitation which would increase snow coverage and reduce albedo etc. etc. But some of the dips in NH temperature are faster than I would suspect. There has to be something more.
Volcanoes are a popular trigger. They are also inconsistent. In fact, with higher average SST they tend to have less impact. That messes up that theory.
Well, enter ozone depletion and dimethylsulfides (DMS). DMS is a natural means of protection of types of plankton. When the solar UV gets too strong, the plankton produce more DMS which is theorized to be their version of sun screen. In the Southern Oceans and the Antarctic Circumpolar Current region, these plankton can go into sun screen over drive when the local winds are higher than normal. The combination of salt spray from the rougher seas and DMS make pretty good Cloud Condensation Nuclei (CCN). More Clouds in the Antarctic would mean more snow to increase the ice sheets and more chemical reations with ozone. Depletion of ozone is a negative as in cooling feedback to climate in general. Since the Antarctic has much few volcanoes than the Arctic, the little plankton provide the cloud seeding and starts the glacial ball rolling.
The relatively new discovery of the Arctic ozone hole and more intense Sudden Stratospheric Warming Events could indicate that sulfides or sulfates with salt spray from the more intense Arctic cyclones this past summer contribute not only to press releases but major energy releases and more NH high latitude snow cover.
Now if that is not crazy enough for y'all. The tropical ozone has also experienced ozone depletion since roughly 1995 which lead to general tropical stratospheric warming, reduced tropical SST and upper 300 meter ocean heat content.
Surprising to some, these occurs coincided with an average deep ocean temperature of approximately 4C degrees which has an effective S-B energy equivalent of 334 Wm-2 which just happens to be the estimated magnitude of the downwelling long wave radiation in the Earth Energy Budget cartoons.
This could be a very entertaining year in Climate Science :)