Criminologists have been writing about this link for decades. Recent research has focused on the exact relationship between temperature, crime rates, and more.
Those who have looked into the question will see that there are both common sense and potentially less obvious mechanisms.
The obvious first: David Hemenway, a Harvard TH Chan School of Public Health professor of health policy, explained to AFP why gun crime is lower when it’s bad weather.
Another, the less controversial idea is heat itself. This is in contrast to weather that encourages people out. It might increase conflict.
There are many reasons for the rise in gun violence in the United States. However, climate change is making it more important to weather.
Warm days during cold months
Hemenway stated that he was interested in the relationship between heat crime and higher crimes since childhood, given the stereotypes of the north-south divide between the United States and Italy as well as the differences between northern European countries such as Scandinavia and the southern Mediterranean.
He co-wrote, in 2020, an article in Injury Epidemiology with his former student Paul Keeping. This paper examined the city of Chicago from 2012 to 2016.
To determine the daily shootings, the paper used data from Chicago Tribune. Then, it compared those to the daily high temperature, humidity, and wind speed.
The researchers found that a temperature increase of 10 degrees Celsius was associated with 34% more shootings on weekdays and 42% more shootings on weekends and holidays.
The researchers also discovered that a 10C warmer than the average temperature was associated with a 33.8 percent higher rate of shootings.
Hemenway stated that it’s not only heat that’s important but also relative heat. “In winter, there were more shots on those days which wouldn’t have been as hot in summer, but were warm enough for winter.”
Leah Schinasi, Drexel University’s lead researcher, published a paper on violent crime in Philadelphia in 2017.
“I live in Philadelphia and remember riding home from work on a hot day to observe how cranky everyone was. She told AFP that she was curious to see if her observation led to higher crime rates on hot days.
Ghassan Hamra, her co-author, found that violent crimes occurred more frequently in the warmer months (May through September) and were higher on the hottest days.
This contrast was most evident on the more comfortable days of colder months (October through April) compared to those days.
Daily rates of violent crime rose 16 percent when temperatures reached 21C (70F), compared to 6C days (43F) in the same period. This is the median for that month.
Hemenway believes both the main hypotheses about the subject, that more people are outside means more hostile interactions and that heat makes people more aggressive, could be true.
The National Bureau of Economic Research published a striking study in 2019 that placed university students in Kenya or California in hot or cold rooms, and measured the impact on various behavioral categories.
It was found that heat significantly affected individuals’ willingness to destroy other people’s assets in the form of gift cards and vouchers.
Hemenway recognized that gun violence has many more drivers than just temperature when it comes to overall issues.
This includes the fact that there were 393 million guns in America in 2020. That’s more than the population. Many states have also taken steps to relax restrictions in recent years.
However, a better understanding of weather could have policy implications. For example, young men could be kept off the streets on hot summer days by engaging in more activities or increasing police presence in key areas that are forecasted.
Hemenway said, “It’s kind of a harm reduction.” “But even if there wasn’t a gun problem here, I think we would find the same thing if there was evidence of fights or assaults. The guns make hostile interactions more dangerous.