AP NEWS

CU Boulder Researchers Link Warmer Days, Increased Crime

November 18, 2018

Researchers at the University of Colorado have established scientific backing for long-held accepted wisdom that rising temperatures can lead to trouble in the streets.

Scrutiny of monthly violent and property crime data from the FBI reported by 16,000 law enforcement agencies across the U.S. cemented the case for a seemingly simple concept: When the weather is more mild, people have more chance to get out and interact — and, to cause trouble.

That dynamic has been dubbed the Routine Activities Theory.

A second, partner theory is the Temperature-Aggression Hypothesis, which holds that people act more aggressively in extreme heat.

Of the two, researchers found the correlation cited in the Routine Activities Theory appears stronger, suggesting that more pleasant days in the winter-time, which can be expected with the continuing onset of climate change, might be a problem for law enforcement -— along with all the environmental effects that are already a focus of concern for people tracking the changes in the planet’s climate dynamics.

“With the Routine Activities Theory, you need three things to come together at the same time and location,” said Ryan Harp, a doctoral candidate in the Department of Atmospheric and Oceanic Sciences at the University of Colorado, who is also affiliated with the Cooperative Institute for Research in Environmental Sciences, or CIRES.

“You need a motivated offender, someone looking to commit the crime and you need a potential victim, and the lack of guardian — someone to prevent the crime; a police officer is the easiest example,” Harp said.

“What we think is going on is that in the winter months people are prone to stay inside and avoid the harsh weather. But if you have milder weather, people are more prone to leave their homes, and you have a greater chance of those three things coming together. ... You are just increasing the chance that those three things can converge.”

Harp didn’t claim this is a link that has not been examined before.

“We are not the first people to go ahead and examine this relationship,” Harp said. “But what we have discovered is that this relationship between temperature and violent crime is much stronger in the winter than in the summer, in general.”

The Temperature-Aggression Hypothesis, Harp said, posits “that if your body is experiencing extreme heat, if you are physically heat-stressed and you get agitated and you are little bit cranky, you are a little bit more likely to do something you might not otherwise do.

“But in our results, we are not seeing as strong a relationship in the summer. We think we have some evidence that the Routine Activities Theory is the stronger driver, but I would definitely not say that we have disproved the Temperature-Aggression Hypothesis.”

Harp and CIRES fellow Kris Karnauskas used powerful climate analysis techniques to probe the relationship between year-to-year changes in climate and violent crime rates in U.S. cities since 1979.

Their methods accounted for the fact that crime rates in most places have decreased markedly since the 1990s. These long-term trends, driven by many societal factors, created the baseline for their analysis.

“Consequently, we considered the crime rate differences from that baseline,” Karnauskas, who also is an associate professor of Atmospheric and Oceanic Sciences at CU, said in a news release.

While the researchers relied on historical climate data from the National Oceanic and Atmospheric Administration’s North American Regional Reanalysis, they drew their crime data from the FBI’s Uniform Crime Reporting Program — pulled by the FBI from tape drives at its West Virginia data center and mailed to Karnauskas’s lab at CU. It included all types of violent crime, from murder down to aggravated assault, as well as burglary, motor vehicle theft and larceny.

The researchers plan more work in this area, and for now, Harp was hesitant to project future trends, in part because it’s hard to forecast what mitigation societies will pursue in relation to climate change. But also, it’s difficult to know how and at what pace people will adapt to the effects of climate change that do occur.

“But I will say, the regions we are seeing the strongest relationship are in the Northeast and the Midwest, and those are the regions that the IPCC (Intergovernmental Panel on Climate Change) is expecting will see the highest degrees in warming. In general, these places that have more harsh winters to begin with are where we are seeing the strongest connection,” Harp said.

Harp is the lead author of the study, which was published Tuesday in the American Geophysical Union’s cross-disciplinary journal, GeoHealth.

Charlie Brennan: 303-473-1327, brennanc@dailycamera.com or twitter.com/chasbrennan

AP RADIO
Update hourly