Wednesday, 25 June 2014

The Little Ice Age: How One Person Can Seriously Screw Up Planetary Climate

If you’re the kind of person who spends a lot of time exploring the Sketchy Science archive, you may have noticed a glaring omission in the topics of articles we have covered. Although we talk about issues of sustainability every now and then (geothermal, solar power, etc.) we have never written an article explicitly about human caused climate change. That is largely because every other science writer around has pretty much beaten that topic to death. The science is obvious to the point of being uninteresting. Everyone knows we are causing the planet to warm and should do something about it. Our job at Sketchy Science is to share weird and cool stuff you might never have heard of, not to tell you what you already know. With that in mind, did you know that some scientists believe that before we got started warming the planet, we may have accidentally dropped it into a mini ice age?

Before we get into the meat of the theory, we should add a disclaimer. This is just a hypothesis. It is supported by evidence and it makes intuitive sense, but the ideas are relatively new and are not widely agreed upon. However, it is a hypothesis that is just too cool to ignore (no pun intended).

You may have already heard of the Little Ice Age but in case you haven’t, it was a period from around the year 1500 to the mid 1800’s where the Earth gave humanity a bit of the cold shoulder. Following the blissfully balmy medieval warming period, the Little Ice Age was an increasingly frustrating time to be alive. Glaciers were growing, crops were freezing, and many people suffered through long, harsh winters following by short, cool summers. In a world where your options for indoor heat ranged from wood burning stoves to coal ovens, the Little Ice Age was a bummer.

Scientists have long wondered about the cause of this glitch in what has otherwise been a fairly agreeable 20,000 year stretch in Earth’s climatic history. Theories have ranged from a drop in solar activity to increased volcanic eruptions cooling off the atmosphere. What people didn’t begin to expect until around 2008 was that we might be able to point the finger at one person. He was an Italian megalomaniac whose genocidal tendencies have earned people in the United States a paid day off work. He is widely regarded as a deeply disagreeable human being who enslaved nations in search of gold. His name was Christopher Columbus.

So how could the no-quite discoverer of the Americas cause the global climate to cool? Well, when he moored his ship in the Caribbean way back in 1492, Columbus ushered in a period of unprecedented ecological change all over the planet. One of the most impactful and most well-known consequences of Columbus’ voyages to the new world was the introduction of European diseases like small pox, measles and a host of other deadly infections to Native American populations with no resistance to them. The outcome, as you probably know, was that within a few centuries over 95% of the indigenous people in North America were dead.

Before all this happened, people in the Americas were pretty busy manipulating the landscapes they called home. Of the many changes they wrought on their land, the one that relates to our topic today was their practice of burning large forested areas to create agricultural land and grasslands on which to hunt large game. As genocide and disease wiped out their populations, the people of the Americas could no longer keep up with the widespread burning program and it is believed that over the same period that so many people were dying off, an area in North America the size of California grew forests where there were no forests before.

Trees are really great things. They are nice to look at, provide us with shade on hot summer days, and they make a great place to build a fort to fall out of and break your arm. They also pull carbon dioxide out of the air and release oxygen. In 2014, this is nothing but good news; in the 1600’s, not so much. Ice cores from Antarctica which trap air bubbles from years gone by have shown that following the arrival of Columbus in the Caribbean, the level of CO­­ in the atmosphere fell by 6 to 10 parts per million. That might not seem like much, but it adds up to about 17 billion metric tons of climate-warming gas locked up in trees instead of in the atmosphere.

Climate modelling computers have demonstrated that removing that amount of carbon from the air could explain most of the cooling of the little ice age. So next time you read about the disappearance of glaciers and sea levels rising, remember the man responsible for putting all that ice there in the first place. Then shake your head in disgust both at one of history’s greatest monsters (aside from Jimmy Carter) and at the modern world for messing things up in the total opposite direction.