At the middle of Greenland, atop two miles of ice, a drill site callled Eismitte got ice core samples down to the bedrock. This is some 100 thousand years of data treasure. Much has been gleened from the ice cores; past temperatures and air composition, and still more treasures of the past to follow. There is an article in the New Yorker (sorry, behind paywall) that puts the situation nicely.
Analysis of the cores showed, in extraordinary detail, how temperatures in central Greenland had varied during the last ice age, which in the U.S. is called the Wisconsin. As would be expected, there was a steep drop in temperatures at the start of the Wisconsin around a hundred thousand years ago, and a steep rise toward the end of it. But the analysis revealed something disconserting. In addition to the long-erm oscillations, the ice recorded dozens of shorter, wilder swings. During the Wisconsin, Greenland was often unimaginably cold, with temperatures nearing thirty degrees lower than they are now. Then temperatures would shoot up, in some instances by as much as twenty degrees in a couple of decades, only to drop again, somehwat more gradually. Finally, about twelve thousand years ago, the roller coaster came to a halt. ... Richard Alley, a glaciologist at Penn State and the author of a book about the ice-coring project, summed up the findings as follows: "For most of the last 100,000 years, a crazily jumping climate has been the rule, not the exception"
So, the ice age was not only cold, it was stormy, with wild capricious weather and megaweather (for lack of a term between climate and weather). Very unstable, with titanic forces battling in the sea and sky. Our interglacial weather is stable and mild by comparison.
The data is harder to find, but a hotter earth also seems to be just as unstable as a colder earth. Hot stormy and shitty.
So, how much time before we fuck everything up beyond repair? Hard to say. Pumping CO2 ironically may have staved off the next ice age (it is inevitable). Perhaps the 1970s scientists were correc tand we were slipping into an ice age, but our own poopy stupidity saved us. But now it seems we've overcompensated.
Other things. I've made some more art.