As some of the climate change skeptics (correctly) point out, it wasn't all that long ago that the big concern was that we would flip back over into an ice age. Given really long tends, that is very likely where the earth will eventually get to. Whether we will survive long enough to see it is another matter.
In any case, there has been one theory about global warming that actually has near term global warming putting us into an ice age, or at least a mini- 2,000 year long one. Essentially what it argues is that the desalination of the oceans (via ice melt) will put a stop to the Atlantic Conveyor currents that are critical for distributing warmth from the equator to places further North. The Younger Dryas, a very nasty mini-ice age, is thought by some to have occurred when a large lake of ice dammed glacier melt, suddenly broke through its icy icy dam and poured into the Atlantic Ocean.
All of which goes a long way to explaining the nervous interest in a current anomaly in North Atlantic temperatures.
Chris Mooney, Washington Post, 24 September 2015 (hat tip: NC)
And there’s not much reason to doubt the measurements — the region is very well sampled. “It’s pretty densely populated by buoys, and at least parts of that region are really active shipping lanes, so there’s quite a lot of observations in the area,” Arndt said. “So I think it’s pretty robust analysis.”
Thus, the record seems to be a meaningful one — and there is a much larger surrounding area that, although not absolutely the coldest it has been on record, is also unusually cold.
At this point, it’s time to ask what the heck is going on here. And while there may not yet be any scientific consensus on the matter, at least some scientists suspect that the cooling seen in these maps is no fluke but, rather, part of a process that has been long feared by climate researchers — the slowing of Atlantic Ocean circulation.
We are already at a low period of activity for the sun, slow down the Atlantic Conveyor currents, maybe add in a Volcano blowing, you would have some seriously existential issues. As it is, it is further evidence that global warming isn't just about having to move a little further north to get comfy. It also threatens to bring us back to the old (really old) normal of highly erratic weather patterns.
Recall that agriculture didn't just start because people figured out how to plant things. It also got started because the climate had finally calmed down enough to wear every few years would bring on some sort of crop disaster. In other words, the planted crops had a reasonable chance of surviving to harvest.
So if the a big collapse, like the Greek Dark Ages, has a ~90% population die off, recall that they could still do agriculture while they were hiding out from their ages Mad Max types, If people have to go back to being hunter gatherers, with the low population densities that allows, something like 99% might be closer.