Thursday, August 30, 2012

High temperatures cause violent crime and implications for climate change

I've posted about high temperature inducing individuals to exhibit more violent behavior when driving,  playing baseball and prowling bars.  These cases are neat anecdotes that let us see the "pure aggression" response in lab-like conditions. But they don't affect most of us too much. But violent crime in the real world affects everyone. Earlier, I posted a paper by Jacob et al. that looked at assault in the USA for about a decade - they found that higher temperatures lead to more assault and that the rise in violent crimes rose more quickly than the analogous rise in non-violent property-crime, an indicator that there is a "pure aggression" component to the rise in violent crime.

A new working paper "Crime, Weather, and Climate Change" by recent Harvard grad Matthew Ranson puts together an impressive data set of all types of crime in USA counties for 50 years. The results tell the aggression story using street-level data very clearly:

Note that all crime increases as temperatures rise from 0 F to about 50 F.  It seems reasonable to hypothesize that a lot of this pattern comes from "logistical constraints", eg. it's hard to steal a car when it's covered in snow. But above 60 F, only the violent crimes continue to go up: murder, rape, and assault.  The comparison between murder and manslaughter is elegantly telling, as manslaughter should be less motivated by malicious intent.

Ranson goes on to make projections about the expected effect of climate change:
Between 2010 and 2099, climate change will cause an additional 30,000 murders, 200,000 cases of rape, 1.4 million aggravated assaults, 2.2 million simple assaults, 400,000 robberies, 3.2 million burglaries, 3.0 million cases of larceny, and 1.3 million cases of vehicle theft in the United States.
This is pretty serious stuff. Ranson also shows that these effects haven't changed much over time, so the prospects for adaptation may be low. And there's no reason to believe that this relationship, which is probably neuro-physiological, doesn't hold outside of the USA.

[cross-posted at FE]


  1. That projection does not make much sense at all, imho. It assumes that base crime rates stay constant over the next 100 years. The A1b scenario has US per capita income grow by about a factor 5 over the next 100 years. I don't buy for a second that crime rates won't be affected dramatically by a five fold increase in per capita income.

    In addition, there seems to be a basic flaw in the computation of the social cost estimates: the per offense values seem to be constant over time, i.e. the VSL for an additional death today seems to be the same as the VSL for a death in 2100, namely $5 million. That would be correct if the income elasticity of the VSL was 0. There is an interesting literature on that topic with many open questions, but one thing seems clear: it is not 0. I think EPA uses something like .5 these days, many international organizations something like 1. Combine that with the income scenarios from A1b and you get completely different cost estimates.

  2. This data is quite accurately built, but perhaps it is only limited into a certain country. People who are living on tropical to country that is near the equator will show different result.