The hotter it gets, the more likely violent crime is, according to a first-of-it-kind study published Thursday in the Journal of Economic Behavior and Organization.
The study, led by Ram Fishman of Tel Aviv University's Department of Public Policy, found that a rise of 1 degree Celsius (1.8 degrees Fahrenheit) correlates with an 1-percent uptick in the rate of violent crime.
This is the first time researchers empirically link the influence of climate change on everyday human behavior. They did so thanks to extraordinary access they had been given to data on all crimes committed in the southwestern Indian state of Karnataka over a six-year period, including the dates, place of the incident and daily weather information.
Known as a “big data” study, it allows for the use of advanced statistical methods to analyze the data in order to isolate correlations between multiple variables in a more precise manner than was possible in the past, in this case, the weather and crime rates.
The study was able to demonstrate that two separate mechanisms were responsible for the causal correlation between the rise in temperatures and the rise in crime. One was an immediate mechanism – it seems physiological, which causes people to behave in a more violent manner when the weather is hotter. This finding matches previous results of studies conducted in wealthy countries.
The second mechanism is slower, and its source is economic: When the seasonal weather during the year was especially hot and caused a drop in crop yields, property crimes increased. “We see a rise in violence on a daily level as a result of the effects of the heat, and we also see a rise in the annual level that is related to the economic losses from drought years, which bring people to a difficult financial situation and which then leads to crime,” said Fishman.
The fact that the weather has an influence on the occurrence of crime has been proven in previous studies, but most examined only the accumulated effect that the weather has on crime over a period of time. The new research is one of the first to identify the two forms of influence: daily and yearly, while differentiating between property crimes and violent crimes, such as murder, rape and attacks on minorities.
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The study’s findings are especially pertinent to Israel, because they prove that even in hot countries whose residents are used to high temperatures, people demonstrate a strong tendency for violence when temperatures rise unexpectedly.
Karnataka has a persistently hot climate and the average temperatures there are between a maximum of 30 degrees Celsius (86 degrees Fahrenheit) to a minimum of 20 degrees Celsius.
The researchers also found that a negative correlation exists between precipitation and crime rates – with an increase of 1 millimeter of rain leading to a drop of 0.3 percent in the probability of a crime being committed.
“Our research is another shining warning sign, for all of those who still needed it, concerning the disastrous and worrying consequences of the climate crisis," said Fishman
The results of the climate crisis are already “here with us,” and they are “eroding the foundations of human society and existence,” he added.
"The analysis we carried out for India can be copied, with the necessary adaptations, for Israel too. I would be surprised if the results here will be different in any significant way."