HKU Bulletin May 2008 (Vol. 9 No. 2)

RESEARCH The Link Between War and the Weather New research sheds fresh light on the catastrophes of climate change. G lobal temperature swings go hand-in-hand with widespread anarchy and destruction as nations battle for dwindling resources, according to a ground-breaking paper from the Department of Geography. Dr David Zhang Dian, Associate Professor and his fellow researcher Harry Lee, postgraduate research student in the Department, have established a firm historical link between the miseries of war, famine and population collapse and periods of global cooling. In their paper Global Climate Change, War and Population Decline in Recent Human History they studied more than 3,000 wars around the world between 1400 and 1900 (a period known as the Little Ice Age) and revealed the relationship of armed conflict to changing weather patterns. This is the world’s first quantitative and scientifically-based study to illustrate the impact of climate change on pre-industrial society. The results show that cycles of war and peace closely follow global temperature patterns. Zhang said: “The concept of environmental conflict has been suggested by several researchers, but they focus only on conflicts caused by short-term climate variations. We studied a long span of Chinese history and found that the number of wars and population collapses is significantly correlated with northern hemisphere temperature variations and that all of the periods of nationwide unrest, population collapse and dynastic changes occurred in the cold phases of this period.” Zhang and his team investigated the data on agricultural production, food prices, population and war numbers and he said: “You can see the successive order, one after the other; after a few years of global cooling, agricultural production goes down and prices go up, when the prices go up the number of wars goes up too. “It follows exactly this kind of order in both Europe and China. In political, cultural and developmental terms Europe and China are at totally different stages during this period and they are totally separate places but the graphs show the same picture. The question is why?” To answer that question Zhang adopted a quantitative and macro-historical approach to exploring the climate-agriculture- war-population relationship. And what he found was a cyclical pattern that followed the weather with a turbulent period followed by a relatively tranquil one. He also looked at the severity of the wars and their impact on human populations by checking a fatality index. This showed two peaks in the colder 17th and early 19th centuries. Two of the greatest population declines since 1400 coincided with these cold periods, while the relatively mild global weather of the 18th century was one of the most peaceful worldwide. Zhang’s theory is that the majority of wars are caused by a battle over resources and he cites the conflict in Darfur and Iraq as examples. “Also the Thirty Years War in Europe, which has been blamed on religion. Okay religion had a role but the real reason was lack of resources. Climate change causes economic turmoil which intensifies social and cultural differences and triggers wars. I’m not saying every war is caused by lack of resources but this is the major cause.” Zhang’s new perspective on history also shows the link between nature and cultural advances. Interestingly, in both China and Europe, the greatest cultural and social progress occurred during the mild periods; the rise of Dynasties like the Early Ming and the early Qing in China and the Renaissance and the Enlightenment in Europe coincided with warmer weather. Research on the living standards of Europeans during the period also reveals that their average height dropped by 2 cms in the 17th century making them the shortest Europeans in two millennia. In the warmer 18th century, when food was more plentiful, they grew again by 2 cms. The impl icat ions for our wor ld today should not be underestimated according to Zhang. “Although this research investigates global cooling this is a warning for our own societies facing a period of global warming. We have been through cool, or cold, periods many times before so in a sense we may be better able to adapt. We have never experienced global warming on this scale; the last ten years have seen the warmest climatic phase of the last two millennia and a dramatic change in temperature – either up or down – is going to have a major ecological impact. Such an extreme change in temperature will certainly tilt the balance of our human ecosystems. “Even though scientists are unable to predict the chain ecological effects induced by climate change we are afraid that it will lead to a shortage of resources like fresh water, arable land and food that will trigger new armed conflicts.” And he added: “It can be argued that we have advanced technology and more robust social institutions that will cushion the impact of climate change, but we also have a much larger population, higher living standards and more strictly controlled political boundaries which restrict migration and these will limit our adaptation to climate change.” 12 13