But literal warming is just one way temperature changes can influence human behavior, study co-author DeLisi noted.
For example, people tend to go outside more when the weather is warmer, which leads to more social interactions.
"In the summer, when people are out, you're going to have more opportunities for people to engage in crimes," DeLisi said.
In addition, changes in weather patterns triggered by global warming could lead to increased poverty, food insecurity, and malnutrition—all of which are risk factors for the development of aggression in violence-prone individuals, DeLisi added.
Global warming could also precipitate violence by increasing "eco migration," or migration forced by some cataclysmic environmental event, he said. (See "Climate Change Creating Millions of 'Eco Refugees,' UN Warns.")
"Displacement and migration of people across borders can potentially lead to a lot more human conflict," DeLisi said.
For example, in the aftermath of Hurricane Katrina, many people from New Orleans moved to Houston. Shortly afterward, Houston saw a spike in the number of homicides, which officials mostly attribute to clashes between displaced New Orleans gangs and Houston gangs, DeLisi said.
If these types of skirmishes occur on a global scale, the result could be increased civil unrest—and even genocide and war, noted the study authors, who presented their work last week at the Sydney Symposium of Social Psychology in Australia.
Global Warming to Make Us Hot and Bothered?
Previous studies back up the notion that global warming could heighten aggression, said Ehor Boyanowsky, a criminal psychologist at Simon Fraser University in Canada who was not involved in the new report.
"My own research has shown that elevated ambient temperatures lead to increased brain temperatures that result in cognitive dysfunction, emotional stress, and aggression, and to higher levels of violent crime," Boyanowsky said.
Heat also has the strange effect of upping physiological conditions—increasing heart rate, for example—while simultaneously making people think they are less energetic, added the University of Michigan's Bushman.
"The fact that hot people are more aroused but think they are less aroused means that they overreact to provocations," Bushman said.