Here's a simple example. If you take a deep bowl, and drop a marble into it, it doesn't take any great intelligence or insight to predict what the end state will be. Marble on the bottom of the bowl. It doesn't matter how high you drop it from or where exactly it hits the sides first. After a bit of rolling around, the marble will stop moving at the bottom.
Now, do the same thing -- but with the bowl flipped over. Where will the marble end up?
Impossible to say, because it is an inherently chaotic system. You could do it a hundred times and the marble will end up in a different place each time, because its final location depends on exactly the speed and angle of its path, where it hits the curved edge of the bowl, even whether the marble is spinning a little or not. A system like this is said to be "sensitive to initial conditions" -- therefore unpredictable. Perturb it a little by altering it in a tiny way, and you get a completely different outcome.
Here's a much cooler example, that I stumbled across in doing research for this post. It's called a double compound pendulum. Take two rigid rods, and suspend one so it's free to swing. Then tie the second rod to the bottom of the first. Start with the rods pulled horizontal, then let it go. Can you predict how the whole system will move?
Simple answer: no. It's a chaotic system.
[GIF is in the Public Domain]
The reason this comes up is because there's decent evidence that the intersection between the Earth's climate and human society is a chaotic system that has at least some degree of sensitive dependence to initial conditions. If you perturb it, it may not respond the way you expect -- and sometimes small changes in one location can lead to big ones somewhere else. (This concept was made famous as "the butterfly effect.")
As an example of this, take the research that was released just last week in Proceedings of the National Academy of Sciences, the link to which was sent to me by a friend and loyal reader of Skeptophilia yesterday. In "Extreme Climate After Massive Eruption of Alaska’s Okmok Volcano in 43 BCE and Effects on the Late Roman Republic and Ptolemaic Kingdom," by a team led by Joseph R. McConnell of the University of Cambridge, we find out about an Alaskan volcanic eruption that may have been one of the significant factors leading to the collapse of the Roman Republic, and its consolidation as an empire -- events that radically changed the course of history in Europe and North Africa.
Geologists on the team identified tephra (volcanic ash) in ice cores from the Arctic that were fingerprinted chemically and shown to come from the volcano named Okmok in the Aleutian Islands. The dating of the tephra deposit shows that the eruption happened in 43 B.C.E. -- right after the assassination of Julius Caesar, during a time when Rome was in chaos as various political factions were duking it out for control. The eruption of this volcano halfway around the world is also correlated with the coldest year Europe had for centuries, possibly longer. Snow fell in summer, crops failed, there were famines and repeated uprisings by desperate and starving citizens.
This sudden drop in temperature was one of the factors that contributed to the realignment of the Roman government as someone emerged who said he knew what to do to fix the situation -- Octavian (later known as Augustus), Julius Caesar's great-nephew. And he did it, establishing the Pax Romana, quelling the revolts and ushering in two centuries of relative peace and prosperity for Roman citizens (and wreaking havoc on the Gauls, Celts, Teutons, and whatever other tribes happened to be in the way of the Roman Legions).
It helped, of course, that once the volcanic tephra from Okmok settled out, the temperature rebounded, and the first years of Augustus's reign were noted for a beneficent climate and rich crop yields. Not all of the good bits of the Pax Romana were due to Augustus's skill as an emperor; he got lucky because of conditions he had no control over and could not have predicted, just as the last leaders of the Republic got unlucky for the same reasons.
The point here is that we should be wary of perturbing chaotic systems, which is exactly what we're doing by our rampant dumping of carbon dioxide into the atmosphere. And what we're seeing over the last decades is exactly the sort of unpredictable response -- some areas experiencing droughts, others floods; deadly heat waves and trapped polar vortexes that drop areas into the deep freeze for weeks; increased hurricanes, tornadoes, and bomb cyclones. One of the frustrations felt by the people who understand climate systems is that the average layperson doesn't see this kind of unpredictability as precisely what you'd expect from pushing on an inherently chaotic system. If you can't make predictions to pinpoint accuracy -- "okay, because the climate is changing, you can expect it to be 95 F in Omaha on July 19" -- it's nothing to be concerned about.
"The scientists don't even know what's going on," you'll hear them say. "Why should we believe it's a problem if they can't tell us what the outcome is going to be?"
But that's exactly why we shouldn't be messing with it. Systems that have sensitive dependence to initial conditions are dramatically unpredictable, and get pushed out of equilibrium quickly and sometimes with catastrophic results.
As the leaders in the final years of the Roman Republic found out.
I feel like another figure from the Classical world -- Cassandra -- for even bringing this up. Cassandra, you may recall, is the woman who was cursed by the gods to having accurate foresight and knowledge of the future, but with the difficulty that whatever she says, no one believes. The climatologists have been sounding the alarm about this for decades, to little effect. If you can't accurately predict the outcome, to most politicians, it doesn't exist.
Which makes me wonder if before we try to get our leaders to get on board with addressing anthropogenic climate change, we should require they sit through some lectures on chaos theory.
I know I sometimes wax rhapsodic about books that really are the province only of true science geeks like myself, and fling around phrases like "a must-read" perhaps a little more liberally than I should. But this week's Skeptophilia book recommendation of the week is really a must-read.
No, I mean it this time.
Kathryn Schulz's book Being Wrong: Adventures in the Margin of Error is something that everyone should read, because it points out the remarkable frailty of the human mind. As wonderful as it is, we all (as Schulz puts it) "walk around in a comfortable little bubble of feeling like we're absolutely right about everything." We accept that we're fallible, in a theoretical sense; yeah, we all make mistakes, blah blah blah. But right now, right here, try to think of one think you might conceivably be wrong about.
Not as easy as it sounds.
She shocks the reader pretty much from the first chapter. "What does it feel like to be wrong?" she asks. Most of us would answer that it can be humiliating, horrifying, frightening, funny, revelatory, infuriating. But she points out that these are actually answers to a different question: "what does it feel like to find out you're wrong?"
Actually, she tells us, being wrong doesn't feel like anything. It feels exactly like being right.
Reading Schulz's book makes the reader profoundly aware of our own fallibility -- but it is far from a pessimistic book. Error, Schulz says, is the window to discovery and the source of creativity. It is only when we deny our capacity for error that the trouble starts -- when someone in power decides that (s)he is infallible.
Then we have big, big problems.
So right now, get this book. I promise I won't say the same thing next week about some arcane tome describing the feeding habits of sea slugs. You need to read Being Wrong.
[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]