Could the Earth be heading for a new ice age?
In a word, no, the insistence of the Internet last week notwithstanding. In fact, any suggestion that scientists have announced otherwise is a bald-faced lie. What scientists—or, rather, scientist, singular—have announced is that in about fifteen years the sun could enter a period of dramatically reduced sunspot activity, a condition last seen during the coldest part of the so-called Little Ice Age.
Valentina Zharkova gave a presentation on solar variation to a group of astronomers last week in which she described her prediction regarding sunspots. Although her research is not new—it’s material she published last year—apparently someone just now realized its potential to cause climate confusion. The logic is that since a lack of sunspots also means a very slight reduction in solar energy output, the Maunder Minimum, as it is called, caused the Little Ice Age and a new minimum will repeat the process.
But I have yet to find any suggestion that these dots were connected by scientists. Dr. Zharkova herself made no claims concerning climate. She had no idea her research would be taken this way; she meant only to talk about sunspots. This is why I’m calling the “scientists say” claims a bald-faced lie.
(Curiously, Dr. Zharkova is a climate doubter, but I have not encountered any suggestion that she is working to foster doubt among other people. She appears to be innocent in this.)
There is a good reason why scientists aren’t running with the mini ice-age idea—it’s full of holes. Most obviously, the Maunder Minimum began about three hundred years after the Little Ice Age started. Perhaps the Minimum deepened the Ice Age, but it obviously did not trigger it. The trigger may have been a series of volcanic eruptions followed by changes in ocean currents.
More subtly, the reduction in solar energy we’re talking about is extremely small. If everything else were equal, it would cool the Earth, but everything else is not equal, and the effect of solar variation on the climate is now completely swamped by the greenhouse effect—at most, we’re looking at somewhat slower warming for a few decades. A new Maunder Minimum can’t save us.
In fact, our current enhanced greenhouse effect makes it harder for anything to trigger a new ice age, and the more greenhouse gas goes into the sky, the higher the ice age threshold will rise—making it less likely the next glaciation will happen at all.
I was not surprised to find that this mini ice age prediction is erroneous. It sounded fishy the first time I heard it because I already knew what sort of things trigger ice ages and I knew that none of them are likely to work in the near future.
I don’t mean to set myself up as something special. I’m sure a lot of people, maybe even most people who aren’t climate skeptics or deniers, had similar suspicions. My point is that if you have a basic understanding of a given scientific field, then you can make pretty good guesses about what’s right and what isn’t in that field. It’s never a sure thing—even scientists are sometimes surprised by their work (they really like surprises, actually). But it’s like knowing a person well; some years ago, a friend of mine was charged with a crime and I knew he had not done it, because I know him. Sometimes people do commit crimes that shock their friends, but that’s pretty rare. In fact, the charges against my friend were dropped for lack of evidence.
This is my working definition of science literacy; knowing enough about a given field to be able to make intelligent guesses about which stories are true and which spurious. I am literate in both ecology and climatology. I am probably close to literate in botany, zoology, medicine, astronomy, and physics. I am not remotely literate in chemistry. I know a little, of course, since there is overlap between it and the fields I know about, but you could very easily construct some chemical malarkey that I’d believe.
How does a person go about becoming science literate in this sense? I wish there were a simple, unambiguous way to do it, but I know of none. A master’s degree helps, but they’re expensive. There are plenty of books and websites out there, but in the beginning it can be difficult to tell the difference between real science and pseudoscience—especially since mainstream opinion is sometimes wrong. How do you tell the difference between a brilliant new theory and something somebody just made up?
I’ve touched on that before and I will again. For now, I’ll just say that in the beginning it is better to go with mainstream scientific ideas, since the scientific process is pretty good at weeding out malarkey whereas the popular press has no such protections at all. Writing a book about how your pet fantasy is “a ground-breaking truth mainstream scientists don’t want you to hear” is easy. Making it through the peer-review process to get published in a reputable journal is hard.
So what does trigger ice ages?
Short-term cold periods can be triggered by volcanism, changes in ocean and air currents, or possibly, yes, solar variation. Human history can also play a part; large-scale reforestation in the wake of the Black Death in Europe (which killed about a third of the population, leading to crop field abandonment) may have helped deepen the Little Ice Age, which was then only a few decades old. It also may not be a coincidence that after a brief warming, the Little Ice Age returned and deepened dramatically after a series of pandemics dramatically reduced the population of the Americas (again causing large-scale crop field abandonment and reforestation) since changes in land-use patterns can alter the carbon cycle.
But the really big glacial advances are generally caused by changes in Earth’s orbit.
The Earth’s orbit varies in three ways: the shape of the orbit shifts from strongly elliptical to nearly circular and back again; the tilt of our axis varies; and which hemisphere has summer while the Earth is closest to the sun changes. All three cycles are very long, in the tens of thousands of years. All three influence the climate, but major glacial advances happen when the cold part of all three cycles coincide.
Or, more precisely, when all three cycles together make Northern summers relatively cool. The Northern Hemisphere has much more land in high latitudes than the Southern Hemisphere does, so when snow on those land masses doesn’t completely melt in the summer, the resulting glaciers get large enough to trigger feedback loops and drop the global temperature still further.
The process takes a long time; from an interglacial to the deepest part of a glacial advance takes tens of thousands of years. It would make a very boring disaster movie. Melting, which happens when the three orbital cycles move out of alignment again, is comparatively quick, but still takes thousands of years. The climate change we are causing now is freakishly fast (and still makes a boring disaster movie).
These orbital variations are not new, of course, but in the last few million years, changes in the shape and arrangement of continents (the creation of the Isthmus of Panama and the Himalayan Plateau)have shifted air and water currents in such a way as to balance the planet precisely between freezing and thawing. Slight shifts in solar energy caused by the orbital variations are enough to shift the balance one way or the other.
The thing is, the warmest part of our current interglacial happened five thousand years ago—we’d been gradually cooling since then, until human activity reversed the trend. Could the Little Ice Age have actually been the onset of a true ice age, interrupted by the Industrial Revolution? I have not been able to find out. But the thing is, anthropogenic climate change is already occurring against what should have been a cooling trend. I was suspicious of the mini ice age because I knew that we’ve already put enough greenhouse gas into the atmosphere to overpower and delay the onset of normal glacial advance.
Which is pretty horrific, if you think about it.