Since we do not have anything resembling good data from the climate prior to the last ice ages it would be pure speculation to say we are on the edge of a new ice age, but there is more evidence than that.
I suspect that during the first millenium after Christ, there was in fact an open Arctic ocean. Remember, Greenland was famable in those days (instead of having glaciers down to the water in all those souther valleys) and was heavily colonized by the Danes. There was much more rainfall in the Mediteranean, especially on the southern side, and the Sahara desert was much smaller. Arabia also had much more rainfall. During Roman times, the middle east was completely deforested, and aquired the climate it has today (semidesert to desert). How much of that was human activity and how much was changing climate is impossible to tell, but I would bet deforestation had something to do with it. Ditto for global warming -- no one seems to want to discuss deforestation, but it has huge effects on rainfall and lower level storm activity. Anyway, there was a distinct "little ice age" in Europe in the 1500-1800 period -- Boston harbor froze shut, the Thames froze solid some years running in the winter (remember, southern England is semi-tropical today -- Plymouth within half a mile of the coast is frost-free, palm trees and all). I have wondered what would happen if the Arctic and Antarctic oceans warmed up. Typically, the very cold water from the ice sheets drops below the warmer salt ocean water and forms the deep "return" stream for the Gulf Stream in the Atlantic. In recent years, the meltwater is warm enough that it is less dense than the saline ocean water, and there is more of it, and it does not sink, rather remaining on the surface. This "cold slug" of mineral depeleted water has had a large impact on the cod fishery, compounding the serious overfishing that was going on. The combination resulted in the collapse of the cod fishery. I have a feeling that loss of icecap may very well result in a re-arrangment of the ocean currents in the Altantic (and probably Pacific as well) -- I wonder what Europe will look like if the Gulf Stream goes across the Atlantic and down Africa instead of up the US coast and over to England? As I tried to point out to my Ecology classes, climate is a metastable system. It will always be be a "closed system". but the actuall flows of water and wind can take any number of self-reenforcing patterns. Land climates will be quite different if the water patterns are different..... Another side note -- the short grass prarie (is in Oklahoma/Nebraska) used to extend all the way into central Ohio.... Peter
