In a world in which many people are worried about global warming, I’ve started to get worried about the exact opposite: global cooling. For I’ve begun to think that, sometime over the next few thousand years, the world is likely to be plunged into a new ice age. And also I’ve begun to think that our current global warming isn’t a bad thing, but a very good thing: it might help stave off the coming ice age.
In this view, I’m strongly influenced by the graph below, of the Vostok ice core:
And what it says to me is that we’re currently living in a warm interglacial period, which has lasted some 12,000 years, and was preceded by about 100,000 years of an ice age. And this has happened four times over the past 400,000 years. There’s a short interglacial period, lasting about 10,000 years, and then there’s a long and deepening ice age, during which it gets colder and colder.
And my reading of this is that, if this has been the trend over the past 400,000 years , then it’s most likely going to continue. And since our current interglacial period has already lasted 12,000 years, we’re very likely somewhere near the end of it.
And it appears that the interglacials start with rapid warming, and end with rapid cooling. It’s almost a flick of a switch from one state to the other.
The Vostok and EPICA ice core data only appeared in about 2007, just when global warming alarmism was at its height. And it may be one of the reasons why Global Warming alarmism was suddenly replaced by Climate Change alarmism around that time, for while Global Warming clearly has only one direction – warmer -, Climate Change can include both warming and cooling. And the ice cores point towards future cooling.
The Vostok and EPICA ice core data may also be the cause of the rise of global warming denialism. It certainly had that effect on me. Why worry about warming when cooling looks far more likely?
And it’s also meant that for the past 9 months I’ve been slowly constructing and improving my own computer climate model. For I had my own idea of how these ice age cycles might work, which was that when the Earth gets covered in ice, the ice acts as a layer of insulation, warming the rock beneath it, which ultimately causes the overlying ice to melt, removing the insulation, and allowing the rock to cool back down again, in a repeating cycle.
It was a nice idea, but it seems that things are a bit more complicated when there’s a sun and an atmosphere above the ice, and so I haven’t got my ice age cycle working (yet).
But since I’ve been thinking about an icy world for the past 9 months, I’ve begun to wonder how humans survived during the 100,000 year ice age that preceded our current interglacial. One simple explanation is that we were confined to equatorial regions during the last ice age, and only started to move north when the ice age ended, and construct increasingly advanced civilizations in Mesopotamia and Egypt.
But there’s a puzzle here. The ice sheets of the last ice age are believed to have covered northern Europe and Asia and America, but not more southerly regions. If the Mediterranean basin remained ice free throughout the ice age, why weren’t there people living there already? Why did they have to wait for the far northern ice sheets to melt before venturing north to colonise the Mediterranean littoral, and start building advanced civilizations around it?
I’ve begun to wonder whether the ice actually extended far further south than is presently believed. What if the ice covered the whole of Europe, not just its northernmost regions? It seems that much of the evidence for the presence of ice sheets is found in subglacial scouring of the underlying terrain, and the construction of moraines. But both of these require the ice to be moving. What if the ice didn’t move? And what if it wasn’t so deep in more southerly latitudes, and had less of an impact on the ground beneath it? Would it have left any traces of its existence?
Accompanying this thought, I’ve also begun to wonder if megalithic structures like Stonehenge were in fact subglacial constructions. And they were so vast because they were intended to hold up a lot of ice. I recently estimated that the dolerite bluestone circle and the inner sarsen stones could have supported about 2.5 km of ice above them. It would also offer an explanation of how these megalithic structures might have been constructed: by hauling the stones across the overlying ice sheets, and lowering them down to where they were needed.
But it is not at present believed that the region of England in which Stonehenge is found was ever covered with ice. Nor is it believed that the stone circles of Göbekli Tepe in southern Turkey were ever covered with ice either.
Why should humans have wanted to construct such subglacial structures? One possible answer might be that, while air temperatures on the surface of the ice sheets would have been far below the 0º C freezing point of water (and may have even fallen as low as -100º C), the base of the ice sheets would have often been slightly above 0º C, and there would have been streams of water flowing through caves of ice beneath them. It would have been warmer below the ice than above it. There may even have been hot springs well above 0º C (the district of Bristol in which I once lived was called Hotwells, because it was once, much like nearby Bath, a thermal water spa where the water reached 72º C ). And if the ice sheets were always melting at their base, it would have also meant that they were slowly descending (at around 1 cm/year, according to my estimates), and it would have been this continual slow descent of the ice that led to the requirement of keeping the ice propped up using earthen barrows or stone or wood pillars. Because if it wasn’t prevented from descending, it would eventually crush everything under it.
If so, these megalithic stone circles would not have been temples or astronomical observatories, but instead robust engineering constructions with a job of work to do. And they were perhaps only needed in a few places, much in the same way that stone bridges are only needed at those places where roads cross rivers. If all the roads and rivers were to vanish, leaving only the stone bridges, people would wonder what purpose they had, and why anyone ever built them.