Civil wars, like the one in Somalia that destroyed this tank, could become more common as the world warms. Image taken by Charles Roffey, used via Flickr CreativeCommons license.
US economists have drawn together 45 sets of evidence spanning 10,000 years to show that warmer temperatures and more extreme rainfall can cause greater human conflict. University of California, Berkeley’s Ted Miguel says this “could have critical implications for understanding the impact of future climate change on human societies”.
“Many global climate models project global temperature increases of at least 2°C over the next half century,” Ted told me. “Our findings suggest that global temperature rise of 2°C could increase the rate of intergroup conflicts, such as civil wars, by over 50% in many parts of the world, especially in tropical regions where such conflicts are most common.”
Scientists have long puzzled over whether data backs climate as a cause of violent events such as the fall of the Roman empire. Global warming has brought an ‘explosion’ of interest from researchers, from archaeologists to psychologists, in climate-linked violence. And the types of conflict vary from fights between two people to civil wars and collapse of whole civilisations. But some studies see political, economic and geographical factors as more important than climate.
How researchers assess their data in these studies could introduce problems. For example, it can often be argued that ‘correlation does not imply causation’, meaning that links between two data sets might be caused by other factors. For example, reading ability might seem to improve as shoe size does, but one doesn’t cause the other – getting older causes both. To find any real, bizarre, link between shoe size and reading ability, you would need to look at people with the same age – or ‘control for’ age.
So Ted and his Berkeley teammates only brought together data that could be used to find causal links, although not all the original studies they started from had done this. Bringing together data from many different studies, collected all over the world, considering different types of violence, gives their findings stronger backing than each lone study. They called on records collected in many places that had taken measurements repeatedly in each place, and analysed them from scratch to reach their own conclusions. Read the rest of this entry »