There will be more violent crimes through the end of the 21st century as a result of climate change, according to a new study.
The study, published in the "Journal of Environmental Economics and Management," showed that climate change will cause an additional 22,000 murders, 180,000 cases of rape, 1.2 million aggravated assaults, 2.3 million simple assaults, 260,000 robberies, 1.3 million burglaries, 2.2 million cases of larceny and 580,000 cases of vehicle theft in the United States between 2010 and 2099.
There are two main theories about why higher temperatures lead to more crime, study author Matthew Ranson said.
"The first is that when temperatures are warmer, there are more opportunities to commit crime. People leave their windows open, more potential victims are out on the streets and people are more likely to get together and interact," Ranson said. "The second theory is that temperature has a direct effect on human aggression. For example, in laboratory studies, subjects make more aggressive choices when they are in a hot room instead of a comfortable room."
Ranson analyzed 30 years of monthly crime and weather data for 2,997 U.S. counties.
The crime data was taken from the Federal Bureau of Investigation's Uniform Crime Reports, which includes monthly information on crimes in the jurisdictions of various police departments.
Historically, serious crime rises in the warmer months of the year.
"Whether you look at daily, weekly or monthly data, there is a strong relationship between historical temperatures and crime. For example, crime rates are highest in warm months of the year. This seasonality is strongest in the northern areas of the U.S., which is where the seasonal temperature differences are also largest," Ranson said.
The social cost of increased crimes as a result of climate change is calculated to cost between $38 billion and $115 billion, according to Ranson. This rise in crime is also estimated to require a permanent 4 percent increase in police forces across the U.S.
"The cost I report in the paper is the cost of victimization, based on evidence such as the value of lost property, medical bills and pain-and-suffering jury awards to victims," he said.
Although, Ranson admits that predicting the future may prove to be difficult.
"We don't know what the year 2100 is going to be like," he said. "What we do know, however, is that climate change is likely to lead to higher temperatures, and historically, higher temperatures have caused more crime. So, while the predictions in the paper could be quite inaccurate, the takeaway message is that climate change is likely to cause a significant increase in crime."
However, not all experts agree. A George Washington University professor said the projected rise in crime is a bit more nuanced than what Ranson reported.
"It's not as straightforward as that. There are some findings that show there is not a linear relationship between crime and temperatures," Sabrina McCormick, an associate professor in the Department of Environmental & Occupational Health at GWU's Milken Institute School of Public Health, said.
The relationship appears to be more like an upside-down U, with lower rates of violent crimes during colder weather and higher rates as the temperature rises. But with extreme heat, the rate comes back down, according to McCormick.
"So, there is the potential that he is incorrect about that [relationship]," she said.
The message McCormick sees in Ranson's research is that climate change threatens the fabric of our society.
However, there are things people can do to help mitigate the effects of climate change, including tree planting and the building of "social capital" in communities where crime rates are high.
"It will empower them to protect themselves and adapt more effectively to climate change," McCormick said.
In Philadelphia, each neighborhood has a block captain, a person who volunteers to act as the community leader on their block and notify the city about problems such as needed street light and pothole repairs, McCormick said.
In the event of a heat wave, the block captain is in charge of going door-to-door to alert neighbors.
Despite a cold winter across the nation, this summer should not have abnormally high temperature extremes.
There will be fairly average temperatures this summer in the eastern United States, AccuWeather.com Senior Meteorologist and member of the Long-Range Forecasting Team Jack Boston said.
"It will be hot and dry from the southern Plains to the Southwest and the Northwest. Burbank, Calif., in the Los Angeles area, is forecast to be above normal during June, July and August," he said. "The northern Plains and Great Lakes will be back and forth with temperatures; Minneapolis will be 1.5 degrees above normal in June, 1 degree below normal and a half degree above normal in August."