Asking a Physicist About the Little Ice Age

According to those detractors, there should be more glaciers in a genuine ice age. 

The last big one, which melted 10,000 years ago, left a sheet of ice a mile high over much of northern Europe, America and Asia.  That was conspicuously missing during the Little Ice Age.  Unless you happened to be in Greenland at the time.

After assuring Liam I'd make certain that all readers know he can only answer questions in general Physics terms (unless black holes crop up), then this was my first query. Was the Little Ice Age really an ice age?

"The IPCC does consider it to be an ice age."  He told me. 

"Who are the IPCC and why should we trust them?"

"The Intergovernmental Panel on Climate Change."  He waited for me to have heard of them, before adding, "The world's leading experts on the climate."

"Do you trust their word?"

Liam laughed.  "Yes."

"Then I do too."  It was an ice age.

My next question came from a reader.  Ragtimelil read what I had to say about the history of the Little Ice Age and asked, 'If the ocean level is rising due to melting ice, why did the levels rise during the ice age?'

Liam explained that much depends upon where glacial activity is taking place. 

The Arctic can deposit all the ice that it wants to into the ocean, and it won't make a difference.  There the glaciers float on the water, so it's simply a matter of swopping ice for seawater. 

The problems begin when the Antarctic glaciers start melting.  They sit on land, so that water has to drain off into the ocean.  That's what raises sea levels.

During the Great Ice Ages, the sea levels were much lower, because of all the water bound up in ice.  But the opposite was true of the Little Ice Age.  The former affected the South Pole; the latter only the North Pole.

He added that it's quite unusual, in the vast scheme of things, for our planet to have glaciers on its poles.

Let me reiterate here that Liam Dodd is not an expert in this period of history.  He's a very good Physicist, but his expertise is largely due to information that I fed him about the conditions, plus some statistics that he was able to dig up.

It's a great overview, but he's careful to tell me that we have to dig deeper for the most up to date and precisely informed thinking in the field.  Academics.  Always covering their backs.

(And for the record, I trust his opinion on this stuff.)

From about 1250, and throughout the rest of the 13th and 14th centuries, temperatures began to drop.  Glaciers crept forward and heavy rain destroyed crops throughout Northern Europe, America and Asia.  Thousands died in famines, especially between 1315-17.  So what had Physics done to us, Liam?

"The reason that it rained a lot is that the cold front was screwed up, due to the encroaching glaciers. This caused the climate cycle to be off.  As the cold front advanced, there was much more stormy weather.  It was hitting the warm front in places where it hadn't before."

By the 15th century, the weather was swinging through extremes. One year would see everyone shivering in the cold all year round, buffeted by terrible storms and unseasonal snow.  The following year would be a heatwave.

Liam had a stark warning, even more unsettling than those weather conditions.  "What happened then is what is going to happen to us soon."  Undeterred by my alarm, he plunged on. "The shifting weather systems caused large variables.  The whole weather system was being knocked out of play."

"So it was like a pendulum?"  I asked.  "The weather swinging around trying to find something it liked?"

"No.  One variable would cause the next."  Liam informed me, in a tone of voice which discouraged thinking of the weather as something sentient.  "It was a positive feedback loop, whereby each climatic event would push the next even further out of whack.  The weather patterns kept changing, because that cold front was colliding with the warm front ever further south."

So a small shift in the weather cycles, around the North Atlantic region, in 1250 had started to escalate off the scale. 

By now, the positive feedback loop meant that the weather systems were becoming increasingly erratic.  That not only explained the back and forth extremes in conditions during the 15th century, but set up the planet for what was to happen next.

Academics of all subjects agree that 1550 was when the Little Ice Age really kicked off.  By now, Liam had his own statistics to support what I was telling him about the history.  He wished to draw our attention to the CO₂ levels between 1550 and 1600.

"From 1550, they show that the planet got colder rapidly.  This was still the positive feedback loop in action.  It just kept on getting colder." 

The frankly terrifying graph below demonstrates this perfectly.  Until the end of the 11th century, the levels of CO₂ were rising steadily, then there's a sudden drop.  The system became unstable, hence all of the terrible weather, but it did keep trying to correct itself.

Then, in 1550, the climate just slipped off the rails. Even if we had no other evidence at all, we could use this graph to pinpoint the Little Ice Age.

Yet the real terror lies in what happens at the end there.  Since the 19th century, CO₂ levels have gone rapidly off the scale.

By the 17th century, our planet was in the grip of a mini ice age, as temperatures plummeted and rivers froze. 

Liam further clarified this for us.  "The changing temperatures meant that the weather systems moved in different ways.  It's like what is happening today, when warm fronts and cold fronts meet in ways that they wouldn't usually.  Sandy was due to two smaller storms colliding, as weather fronts shifted, causing a monster storm instead.

"That's also what they experienced during the Little Ice Age."

So what happened next?   We patently came out of it!

Liam could read that story into the CO₂ statistics too.  "From 1760, the CO₂ levels rose; then plateaued by 1800.  This brought more settled weather and stabilized the weather systems."

As an historian, I could provide some further explanation here.  His Physics data had just deposited us into the Industrial Revolution.  Under the weight of heavy industry, humanity had begun burning a lot more fossil fuels.  It seemed like we'd saved ourselves!  Go us! 

Or had we?

"No."  Liam blithely informed me.  "The world began warming again before the Industrial Revolution.  The theories about that ending the Little Ice Age simply don't work when you look at the Physics.  But it did upset that recovery in the opposite direction.  It's sent us straight into another positive feedback loop, which is just now beginning to spiral out of control.  Expect more extremes of weather.  It's already begun."

One thing which did puzzle me is why science hasn't yet come up with the definitive answer.  We have dozens of theories, but no climatologist stating, "It was this!  Let's not do that again!"

Liam blamed the data.  "Unless we discover more evidence, there is no definitive answer." 

The trouble is that the kind of statistics that we keep today weren't kept by Medieval meteorologists.  We can only extrapolate from what they did report, or from the evidence trapped in ice cores or tree rings.

Even those scientists steeped in this field, educated and highly informed guesses are all that they can provide.  So let's explore some of those theories.

"From 1645-1715, the Maunder Minimum fits perfectly with the dates of the worst years of the Little Ice Age.  Before that were the Wolf and Spörer Minimums.  It's all way too exact to be entirely coincidental."

But what does that all mean?

"Low solar activity means that there is less energy reaching the Earth from the sun.  Historically, low sun spot activity has led to colder temperatures on Earth."

However, Liam was also cautious about this data.  "The evidence is controversial; and we don't fully understand the connection between sun spots and temperature.  We just know that historically it has worked.

"Plus this doesn't make sense over a short period of time.  It can only be seen in a long cycle."

He further warned that the correlation is no longer working.  Further evidence that we're currently in a positive feedback loop, where all the rules no longer apply?  I never thought to ask him!

"Massive changes in population can alter weather.  There's a lot of evidence that Genghis Khan's wars did have an effect on the climate. 

"There are also two studies which argue that the collapse of the Native American population, after 1500, created wildernesses and forests, where there had once been arable land." 

Liam has provided links to those studies, so that we can read for ourselves.  However, he isn't convinced that this was a factor in causing the Little Ice Age.  He added, "The evidence is contradictory in this case."

I did point out that prior to the Little Ice Age, in the Medieval Warm Period, the population had grown faster than ever before.  But the 14th century had also devastated it.  Between famine, freezing temperatures, the Black Death and wars, the numbers of human beings on the planet had severely slumped again.

Liam saw nothing there to change his earlier opinion that the evidence is too contradictory to fully account for the Little Ice Age.

This was a contemporary theory. It resulted in the major witch-hunts, after Pope Innocent decreed that this was the reason behind the terrible weather.

"The Pope should apologize." 

Liam's response led to a vaguely tongue in cheek discussion of this one, as I'm a Wiccan.   Our joint conclusions were that this might have had an indirect effect on the conditions of the time.  After all, over 35,000 men, women and children burnt at the stake means over 35,000 less mouths to feed in a famine.

Plus there's all that wood being cut down for the fires, leading to further deforestation and increased levels of CO₂ in the atmosphere. 

So, if this was to happen again, should people like me be subjected to religious genocide to correct it? 

"Witches didn't affect the weather."  Liam concluded, as a scientist always would.  "And the method of execution effects are too negligible to have factored into the climatic changes at the time."

That's a relief.

Also, as a Wiccan historian who wrote a dissertation on the subject, I can categorically state that there is nothing in our lore which suggests guilt.  Witches (and occultist Dion Fortune) did claim responsibility for the storm which blew the Spanish Armada off course in 1588.  But that's it.

"It is entirely possible, with regard again to a positive feedback loop.  But unlikely in this instance." Liam pondered it.  "There are so many things which could have contributed.  You have to account for Milanković Cycles, volcanic eruptions, as well as the after-effects of the Medieval Warm Period just before.  Massive changes can be wrought by deforestation.

"To say it's natural is to discount a lot of data."

He went on to describe two studies, which were independently published in 1999 and 2006. They both demonstrated that the inherent variability of the climate isn't enough to account for the Little Ice Age.

Liam provided links to both of them, so that you can read those findings for yourself.

This is a third contemporary theory and resulted in massacres and/or expulsions of Jewish people in several European countries.

"Antisemitism has been rife in many centuries, and it was particularly advantageous in the Middle Ages."  Liam seemed to remember who he was talking to.  "This isn't a Physics theory.  Ask an historian!"

As an historian, I can confirm that Jews got blamed for everything that couldn't be pinned on witches (and some other things besides).  It's difficult to work out how precisely they may have affected the climate though.

I think we can safely put this aside as prejudice and state that, from both a Physics and History perspective, there's absolutely no credence in the theory.  Though, for completion's sake, I suppose I ought to check in with a Jew.

"Sheri!  Did your lot go causing ice ages in the Medieval and Post-Medieval period?"

My fellow Wizzley author responded, "I have looked into the issue and I can honestly say that I do not know how my ancestors would have been able to play around with sunspots, ocean currents, volcanic activity or anything else that has been suggested as responsible for the climate changes at that time."

That's cleared that one up then.

I'd nearly run out of theories to run by my Physicist, so I turned to my final question.  It must be one in the minds of many people by now, particularly with all of this talk of modern climate change. 

Could the Little Ice Age happen again?   I was hoping for a resounding no.  I didn't get it.

"In the current climate, we don't know.  We're in untested waters."  Liam was referring to the fact that the meteorological records have never looked quite like they do in the 21st century.  "There is no evidence about what happens when we heat up in such a short period of time. Global temperatures are predicted to rise five degrees in the next 100 years.  We're just getting hotter and hotter.  

"Unless something big happens, not going to have anything like the Little Ice Age for a while. But we don't know.  As I said, we're in untested territory.  It's going to get hotter and wetter, stormy, and we're unlikely to get summers. India will bake. The Sahara will flood; or not.  We don't know."

There was one related theory, which I hadn't mooted yet.  I asked it now.  "What's your opinion on the fact that there is no such thing as global warming?   We are, in fact, still coming out of the Little Ice Age."

"They're wrong."  Liam pulled no punches.  "They are misunderstanding how climate works. Temperatures do go up and down, but the Little Ice Age was relatively rapid.  We've gone up way too rapidly for it to have been natural conditions."

And that's all!   Thank you very much to Liam Dodd for taking the time out of his studies to look at this fascinating moment in history.