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With over two thirds of the world’s population expected to live in cities by 2030, the climate-crime connection cannot be ignored
By Mac Margolis and Robert Muggah
The notion that warmer weather can make us more violent is not new. The link between mercury and murder is a familiar trope of pulp fiction and the classics. 'These hot days, is the mad blood stirring,” Benvolio says before the Capulets and Montagues duel in the streets of Shakespeare’s sweltering Verona.
Scholars have been quarrelling over the topic since the 19th century, but accelerating climate change promises to fever the debate. If we believe, with Montesquieu, that excessive heat saps the body of vigor and dulls the mind, a growing number of sociologists, psychologists and criminologists warn that extreme weather is fuel for violent crime and delinquent behavior.
Former Scottish prison governor David Wilson once lobbied to have air conditioning installed in some of the country’s most violent prisons on a bet that colder temperatures lead to cooler heads. Wilson, a criminologist, noted that August is the cruelest month, citing studies pointing to a 10 percent increase in murders in the dead of Scottish summer. His prison campaign fell short – on grounds that convicts shouldn’t get to chill on the tax-payers tab.
Today there is considerable research indicating that certain climate-related shocks and stresses can trigger both violent and non-violent crime. While the extent of these connections varies, the available evidence suggests that warming temperature and intensifying pollution can provoke a substantial increase in crime, starting in the most densely inhabited and vulnerable areas.
With over two thirds of the world’s population expected to live in cities by 2030, the climate-crime connection cannot be ignored. Greenhouse gas emissions and warming are already intensifying heat islands, contributing to water shortages, raising sea levels, increasing flood-related risks and worsening air quality, especially in large and fast-growing cities in Asia, Africa and the Americas. The stakes are highest in the most vulnerable neighborhoods and households, already burdened by deep inequities and compounded disadvantages.
Freak weather and punishing heat – especially heat - are injecting new urgency into the centuries’ old debate. Until recently, most U.S. cities were celebrating a historic, three-decade decline in murders. Then the summers started heating up, and so did the rate of criminal violence. About twice as many people were shot in Northern cities like Chicago, Milwaukee and Detroit during the hottest spells compared to the colder months, the New York Times reported in 2018. (Violent crime also rose during summer in southern cities, albeit less dramatically.)
The dangerous relationship between warming and crime wasn’t just apparent in the U.S.. In a global study of 57 cities between 1995 and 2012, Dennis Mares and Kenneth Moffett associated a one degree Celsius rise in global temperatures with a 6% increase in the prevalence of homicidal violence.
Part of the explanation is intuitive. Rising temperatures generally send more people into the streets, and a higher number into mischief or worse. Granted, it’s not exactly a straight shot from a heatwave to felony. Unbearably hot days, for example, could have the opposite effect - keeping people indoors or in Montesquieu’s stupor of lassitude. Yet don’t underestimate our lesser angels.
Not all weather-related crime is violent. As the outdoors beckons in high summer, an abundance of prospective victims and unguarded homes is catnip to burglars. With temperatures rising last month, the Irish Garda, or national security force, alerted Dubliners to bolt their gates, adjust their security cameras and keep their car windows shut against summer opportunists.
More recent theories about the relationships between climate and crime come from behavioral science and neurology. Drawing on experimental research, the central claim is that even subtle alterations in weather or exposure to pollutants can sway individual judgment and control. When people are exposed to changes in their environment – say, increased heat or exposure to specific pollutants - their underlying behavior may change, often for the worse.
For all the disruption, however, urban authorities have been slow to respond to the climate crime challenge. We may no longer have that luxury. As extreme weather becomes the new normal, city keepers should map out the most vulnerable zones and pay closer attention to poorer, minority and under-served communities that are facing the most severe risks and egregious consequences.
There is a real danger that answering crime spikes with blunt force policing can exacerbate existing inequities and insecurities. Get-tough law enforcement and stiffer penalties, for example, could unleash repressive responses with damaging consequences for poorer, minority and excluded groups.
There are multiple and interconnected benefits to be had from investing in structural overhauls, starting with green nature-based investments for more sustainable urban living. Reducing heat islands, raising green roofs, expanding parks and tree-cover, while scaling back pavement and concrete are all initiatives that can bring crime reduction dividends by lowering temperatures and slashing emissions of the many gases (CO2, NO2 and PM2.5) that foul city skies.
Likewise, reducing potentially behavior-deviating air pollution is especially cost effective not just for improving population health, but by preventing crime. Tightening environmental policies, including emissions standards and congestion pricing may likewise make our cities cleaner and safer.
Bigger cities and much warmer weather are part of a changing world, but also a call to action. By working now to mitigate the worst effects of extreme weather and redressing the environmental injustices in our cities, urban authorities can help not only to prevent a climate crisis from becoming an emergency, but also spare lives and livelihoods as well.
Mac Margolis is an advisor to the Igarape Institute and a long-time correspondent and writer based in Rio de Janeiro. Robert Muggah is co-founder of the Igarape Institute and principal of the SecDev Group.
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