Does global warming increase violent crime? Here's someone who says so. - Telegraph.co.uk (blog)

Could global warming be making people more violent?

Global warming has been blamed for many things. But crime? Improbable as it may seem, a paper recently published by Harvard University is suggesting just that.

The paper, from the University’s Kennedy School, puts up a fairly convincing case that violent crime rises with the thermometer. In fact, that’s nothing new and other researchers has demonstrated so in the past. But Matthew Ranson, a PhD student and the author of the paper, seems to have done a particularly comprehensive job, analysing monthly crime, temperature and rainfall records across 2,972 US counties for the entire half century, 1960 to 2009 â€" including from 17,000 law enforcement agencies.

He found “a striking relationship between monthly weather patterns and crime rates”, with murders, rapes, assaults and similar crimes increasing in step with temperature. Property crimes, like burglary and larceny, similarly increase as it gets warmer, but only up to the modest level of 40 degrees Fahrenheit, after which the rising thermometer has little effect.

What’s the explanation? Some believe that warmer weather brings more people out on the streets, giving greater opportunities for mugging and conflict, but if that were true it should also presumably make theft from them more common. Or it may be that increased hear would simply make people more aggressive; there is some scientific evidence for this, finding people in laboratory conditions more likely to try to hurt someone who has criticise them when it is hotter.

Be that as it may, if rising temperatures do boost crime, it might be logical for them to go on doing so and thus Ranson predicts that “climate change will cause a substantial increase”. However he then â€" and this is where credulity become seriously strained â€" he goes on to suggest that, if global temperatures rise by some five degrees Fahrenheit between now and 2099, as the Intergovernmental Panel on Climate Change has suggested “there will be an additional 35,000 murders, 216,000 cases of rape, 1.6 million aggravated assaults, 2.4 million simple assaults, 409,00 robberies, 3.1 million burglaries, 3,8 million cases of larceny and 1.4 million cases of vehicle theft” in the US over what would have occurred without the climate change.”

Such precision is hard to credit. Besides, violent crime has been decreasing for decades in the US even as global warming has begun to take hold. Changes in policing tactics, legislation and social and economic conditions are all likely to have a greater effect. And, people may simply change their behaviour by adapting both to warmer conditions and rising crime, for example by not going out so much.

Ranson has accepted that “there are so many things that are going to change over the net hundred years, (that) almost any kind of prediction of this type is going to include a lot of error.” But he added that, while he “would not treat these numbers as ‘this is what’s going to happen’” they nevertheless showed “the general magnitude of what effects we would expect, based on what has happened in the past.