THERE IS a country called Tuvalu that consists of several small islands in the middle of the Southern Pacific. For the past decade, 75 Tuvaluans yearly have left their country and immigrated to New Zealand. Is Tuvalu under war? Did another country colonize it? Or has it been hit by a giant meteor? All wrong – Tuvalu is all but under the danger of sinking. In 2001, the International Panel of Climate Change (IPCC) announced that the average sea level might rise as high as 88 more centimeters, which means that countries consisting of islands like Tuvalu could be left entirely submerged because of global warming. Recently, an interesting study conducted by researchers at the University of California Berkeley and Princeton University was published in the August edition of *Science*. The study predicts that global temperatures, on average, will rise 2°C in the next 50 years. What is more, the study revealed an intriguing fact: climate plays an influential role not only in changes within the ecosystem but also in human affairs, particularly human behavior around the world. What is global warming and how does it affect us?

What it means to be heating up

When the topic of global warming is addressed, it is often paired with a similar concept – climate change. The two terms are at times wrongly used interchangeably, and Woo Nam-chil (Prof., Dept. of Earth System Sciences) emphasizes that differentiating between the two concepts is essential to discussing either term. According to Woo, climate change is a more inclusive term. “Climate change can mean that earth’s surface temperature increases in some regions and decreases in others.” Woo adds that global warming is one of the causes of climate change. Hence, the two terms should not be used interchangeably, but instead should be identified as a cause-and-effect pair.
Now with the two terms distinguished, the next natural question that arises is: just what is global warming? *Oxford Dictionaries* may be able to answer the question. It defines global warming as “a gradual increase in the overall temperature of the earth’s atmosphere generally attributed to the greenhouse effect caused by … pollutants.” Woo casts extra explanation on the two main causes of global warming. The first is, as many people are aware, human activities like deforestation and the burning of fossil fuels. The other, often less recognized cause, comes from natural processes, like modifications in the earth’s orbit or changes in the intensity of sunlight. To the surprise of many people, global warming is part of a pre-existing natural cycle that came from these natural processes. In fact, there were times in the Cenozoic era when global temperature has fluctuated as much as 10℃ in a period as short as 10 years. Nevertheless, adds Woo, “Global warming becomes a problem when the chemical balance of the world is interrupted by human intervention.” And this is what is happening today with human activities.
As the phrase “gradual increase” in the Oxford definition hints, humanity has long been aware of global warming. In fact, even the ancient Greeks held debates about how cutting down trees could bring more or less rainfall in the region that would consequently affect the average temperature. However, nobody could pinpoint what exactly *caused* global warming. People could assume that human activity had some kind of association, but it was only a guess work until a Swedish scientist named Svante Arrhenius, now honorably named “the father of climate change science,” discovered in 1896 the correlation between carbon dioxide (CO2) levels and the earth’s surface temperature. After meticulous data collecting and more than 10,000 calculations later, Arrhenius speculated that doubling CO2 levels would cause an increase in global temperature of 5 to 6℃. (Scientists today believe the same increase in CO2 levels will cause a global temperature increase of not 5, but around 2 to 3℃.) Arrhenius’ research brought climate change science to a new discovery milestone: global warming is caused, at least partially, by excess CO2 produced by humans.

It heats up the people, too

It is all too well known that global warming causes the melting of glaciers, the rising of sea levels, and changes in the ecosystem. However, it is not as easily recognized that the effects of global warming also stretch far enough to affect human behavior and, by extension, society. It is not always easy to realize that everything is related to each other, especially for two seemingly unrelated topics like these. This model that views all components of the world as an interrelated and interdependent whole is called a “complex system.” Based on this definition, Woo claims that when approaching any problem, we should consider them not as individual issues, but as components of an interconnected system.
This idea of complex system is where the UC Berkeley and Princeton University research teams co-led by Solomon Hsiang and Marshall Burke started off. Their research brought together a variety of academic fields – including climatology, archaeology, economics, political science and psychology, -to investigate how two components of the complex system – global warming and human behavior – are interrelated. According to their research, the littlest trigger of a 2℃ increase in global temperature within the next 50 years will result in a rise in three types of violent human behavior: personal violence like murder and rape, intergroup violence and political instability like civil wars and riots, and finally institutional breakdowns including possible collapses of major civilizations. Of the three types of violence, the rate of intergroup conflicts is expected to increase the most pronouncedly by over 50%. This is not only a prediction of the future. According to the study, it is estimated that conflicts have erupted more frequently in regions impacted by drastic global warming. For instance, it is now estimated that the reason for the collapse of the Mayan civilization was partially due to global warming. Global warming created hotter and drier periods that sporadically appeared between 200 and 1100 AD in Maya that coincided with times of societal upheaval. Douglas Kennett, an anthropologist from Penn State University, explains that such conflicts occur because of the difficulties associated with survival. Woo asserts that violence in today’s world can be explained along similar lines. With hotter and drier temperatures, it becomes harder to grow food, which results in fights for survival. “Hotter climate causes changes in the ecosystem which leads to difficulty in cultivation. This becomes the source of violence.”

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The UC Berkeley and Princeton University research is just one of the many scenarios that try to predict the blurry future of global warming. However, Woo emphasizes that we must never forget that they are predictions made based on incomplete data. “Today’s predictions cannot be accurate, because there are too many factors to consider that we do not know of yet.” If we wish to accurately predict how the human world will change as a result of global warming, we must consider everything about the human mind. But can we? No. There are too many idiosyncrasies of the human mind that science simply cannot predict or control – the human mind is yet another complex system on its own. Right now we only know one thing for sure: the world is heating up. The climate is changing and so is our ecosystem. And so are we.