Yesterday I read in Wikipedia:
Based on past estimates for interglacial durations of about 10,000 years, in the 1970s there was some concern that the next glacial period would be imminent.
Back in the 1070s was when I spent much of my time building electronic heat flow models, but knew next to nothing about glaciations.
Now that I’ve become interested in ice ages, I’m a bit concerned that the next glacial period (ice age) could be imminent. So I’ve begun to think like some people did back in the 1970s.
But, as we all know, things have moved on a bit in the intervening 50 years. For the climate scientists all seem to have stopped worrying about an impending ice age, and have instead been worrying about Anthropogenic Global Warming. It’s become a very hot political potato indeed.
So why did the climate scientists change their minds, and start worrying about warming instead of cooling?
However, slight changes in the eccentricity of Earth’s orbit around the Sun suggest an extended interglacial for about 50,000 years.
“Suggest”? Is that all?
Models assuming increased CO2 levels at 750 parts per million (ppm) current levels are at 407 ppm have estimated the persistence of the current interglacial period for another 50,000 years. However, more recent studies concluded that due to the amount of heat trapping gases emitted into Earth’s Oceans and atmosphere, that this will prevent the next glacial (ice age), which otherwise would begin in around 50,000 years, and likely more glacial cycles.
So they seem to think that slight changes in the eccentricity of the Earth’s orbit mean that we’re going to continue in a very long interglacial period. And in addition CO2 in the atmosphere will likely ensure that we never see an ice age again.
Now that they’ve discounted any possibility of global cooling, and of a new ice age starting, the only thing left to worry about is global warming. And so that’s what they worry about.
They may be right, but all this supposes that they have a good understanding of how ice ages begin and end. But the Wikipedia Ice Age article, which is presumably written by climate scientists and glaciologists, doesn’t seem to think this is the case:
The causes of ice ages are not fully understood for either the large-scale ice age periods or the smaller ebb and flow of glacial–interglacial periods within an ice age.
And in my copy of Raymond Pierrehumbert’s Principles of Planetary Climate, in Chapter One he starts listing the Big Questions:
Some of these questions have been answered to one extent or other, but many remain largely unresolved.
Of the Snowball Earth, when the whole Earth may have been completely covered in ice, he writes:
The Snowball phenomenon is pregnant with Big Questions. the most obvious of which are: How do you get in? How do you get out? And if your planet does succumb to a global Snowball, how long does it take to get out again? Is it a matter of centuries, millions of years, or billions of years?
Does this sound like someone who has got all the answers? It sounds to me like someone who hasn’t got all the answers at all. Pierrehumbert has lots of Big Questions, and they include lots of Big Questions about ice ages.
So if nobody really knows how ice ages begin and end, why is anyone sure that one isn’t going to start for another 50,000 years? Or that CO2 in the atmosphere will stop them happening forever?
I don’t trust these climate experts. I don’t trust them about global warming, and I don’t trust them about the supposed absence of cooling either. And that’s why I’m building my own models.
You can’t trust anyone these days. I think that there are honest people like Pierrehumbert who will readily admit to not knowing lots of things, and there are less honest people who will pretend to know far more than they really know. Unfortunately it’s the latter sort who seem to dominate the airwaves. Yeats:
The best lack all conviction, while the worst
Are full of passionate intensity