Violence and temperature

Last Saturday, the Arizona Daily Star ran a story about some research which claims that global warming will cause increased violence. As usual with stories of this type, the Star goes with the scary headline but fails to get the rest of the story.

The study in question is “Quantifying the Influence of Climate on Human Conflict” by Hsiang et al. The abstract reads:

“A rapidly growing body of research examines whether human conflict can be affected by climatic changes. Drawing from archaeology, criminology, economics, geography, history, political science, and psychology, we assemble and analyze the 60 most rigorous quantitative studies and document, for the first time, a remarkable convergence of results. We find strong causal evidence linking climatic events to human conflict across a range of spatial and temporal scales and across all major regions of the world. The magnitude of climate’s influence is substantial: for each 1 standard deviation (1s) change in climate toward warmer temperatures or more extreme rainfall, median estimates indicate that the frequency of interpersonal violence rises 4% and the frequency of intergroup conflict rises 14%. Because locations throughout the inhabited world are expected to warm 2 to 4s by 2050, amplified rates of human conflict could represent a large and critical impact of anthropogenic climate change.”

Pierre Gosselin, proprietor of the blog “NoTricksZone” reports on critiques of the research. Pierre is an American citizen living in Germany who provides translations of European happenings. He is a graduate of the University of Arizona.

A more complete story of the research ran in the German paper der Spiegel and Gosselin notes “The Hsiang study is even too absurd for the leftist Spiegel to swallow.” So, the Spiegel asked some other experts to assess the research. They found that the data were cherry-picked:

“Jürgen Scheffran, Professor for Climate Change and Security at the University of Hamburg and his colleagues evaluated 27 studies and found that 16 were statistically significant in showing that global warming increased the probability of violent conflict, but that 11 studies said they could actually have the opposite effect, i.e. decrease the likelihood of violent conflict. Eight of these papers were not even considered by Hsiang and his colleagues, Scheffran says.”

Oslo economist Halvard Buhaug said, that Hsiang used only the strongest data that supported their thesis while ignoring the rest.
Jochem Marotzke, Director of the Max-Planck Institute for Meteorology in Hamburg pointed out that Hsiang et al. failed to consider alternative hypotheses.

Richard Tol of the University of Sussex pointed out that Hsiang et al. actually evaluated studies that had to do with weather phenomena, not climate.

See Gosselin’s full post here.

A long article in the British Journal of Criminology by Ellen O. Cohn concludes that some crimes do increase with temperature up to about 85 F, then decline:

“A few firm conclusions can be drawn from the research conducted to date on the relationship between weather and crime. It appears that assaults, burglary, collective violence, domestic violence, and rape tend to increase with ambient temperature, at least up to about 85°F. The relationship between heat and homicide is uncertain. High temperatures do not appear to be correlated with robbery, larceny, and motor vehicle theft.” Some of these crimes may be influenced by increased alcohol consumption as temperatures rise. There appears to be no correlation of crime with cold weather or rainfall.

Finally, from ScienceNews we find a report that contradicts Hsiang:

“Some of Eastern Europe’s greatest wars and plagues over the last millennium coincided with cold periods, scientists report online January 14 in the Proceedings of the National Academy of Sciences….The Black Death in the mid-14th century, the Thirty Years’ War in the early 17th century, the French invasion of Russia in the early 19th century and other social upheavals occurred during cold spells. The team suggests food shortages could explain the timing of some of these events.”

Now that you know the rest of the story, we see that the Star’s global warming scare is just more junk science. We can add this to John Brignell’s long list of things allegedly caused by global warming.