Ancient Farms Cause Alarm!

Izzy Cowan, Writer

We all know that the Industrial Revolution was a huge turning point for humanity – and for our planet.  As new gas emissions started to be released into the atmosphere, global temperatures gradually increased.  I know what you’re thinking. You’re thinking that this is going to be another article about how people are destroying the environment and how global warming is becoming a bigger and bigger problem.  As much as these things are true, that’s not the only thing I’m here to talk about. Today, we’ll be going a little further back in time than the Industrial Revolution.

First, let’s talk about the Ice Age.  No, not the movie. The actual, historical Ice Age that ended approximately 12,000 years ago.  What caused this period of perpetual glaciacion? The answer is Milankovitch cycles. Milankovitch cycles are periodic changes in the way Earth orbits the sun.  These include the switching of Earth’s orbit from being more circular to more elliptical (oval-shaped, or elongated), as well as changes of the manner in which Earth tilts and wobbles on its axis.  Naturally, these changes affect the climate of Earth, as our climate is dictated by the way sunlight hits our planet. The cyclic changes of the Milankovitch cycles have been predictable by scientists throughout most of Earth’s history, so you can imagine their surprise when their studies showed an odd change in the history of Earth’s climate that was not consistent with these cycles.

Scientists have compared Earth’s current time period, called the Holocene, to a similar one that happened about 800,000 years ago, which is called MIS19.  MIS19 shows patterns similar to those of other interglacial periods in the past, where it started with a very high concentration of both carbon dioxide and methane, which slowly decreased over thousands of years until the climate of Earth was significantly cooler.  At this point, Earth would typically enter an Ice Age. So, if the Holocene is so similar to MIS19, why isn’t the planet covered in ice? Why isn’t Scrat chasing his acorn through our backyards?

An answer may come from a theory called the Early Anthropogenic Hypothesis, developed by scientist William Ruddiman at the University of Virginia, who studies the historical climate of Earth.  Ruddiman states, “I noticed that methane concentrations started decreasing about 10,000 years ago and then reversed direction 5,000 years ago and I also noted that carbon dioxide also started decreasing about 10,000 years ago.”  Why would this be? Why would Milankovitch cycles, which had always been so consistent in providing explanation for the climate of the Earth, fail to provide an explanation for this phenomenon? Ruddiman believes that ancient agriculture introduced greenhouse gases into the atmosphere that permanently changed the course of Earth’s climate.  Ancient farming systems, such as rice paddy systems in northeast Asia, were a significant source of methane. Deforestation in Europe and other farming systems of early Asia were also major sources of greenhouse gases, all beginning about 5,000-7,000 years ago.

According to Science Daily, the Earth would have been entering another Ice Age by the beginning of the Industrial Revolution had it not been for human influence through agriculture and other greenhouse gas-releasing projects.

So what does that tell us about the future of our delicate planet?  It turns out, you were right about this being a cautioning global warming article.  If human influence 5,000 years ago was enough to set the climate of Earth spinning, what could we, with all our fossil fuel emissions and power-demanding technologies, be doing to the climate of our planet?  According to Ruddiman, we may have found ourselves in a situation where we are trapped in an interglacial period that only gets warmer and warmer. However, we also saved ourselves from thousands of years of human work being smothered in snow and ice.  Is there a happy medium between bitterly cold and suffocatingly hot? Only time will tell how future scientists will go about dealing with climate. Based on how humanity was able to permanently alter the climate in the past just by trying to maintain a steady food source, there is much hope for being able to change the climate of the future.