Crime Rates And Climate Change – Is There a Link?

Whether we believe it or not, whether we like it or not, we have all heard a lot about climate change. Our love affair with fossil fuels has swathed the Earth in greenhouse gases; trapping them within the atmosphere. Planetary temperatures have increased, bringing about extreme weather events. Violent and intensified climatic events are in the news so much nowadays that they are almost becoming the norm. Climate denialists have less and less of a foot to stand on as the storms, floods, droughts and heatwaves hit with more frequency and with more devastating effect. 

As the temperatures rise and scientists count the cost on natural resources, they have to ask tricky questions like “How are we going to feed the exploding human population on a collapsing global ecological system?” Or, “Where is everyone going to move to when the sea level rises flooding coastal cities?” Or, “How can we mitigate disasters caused by extreme weather events?” With these enormous predicaments to face, little attention has been given to the subtler consequences of climate change. How it affects the psychological and sociological health of humans, and how it will change our behavior with regards to aggression and ultimately violent crime. In this post, we will explore the connection between weather and crime.

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Weather and Crime


Humans are warm-blooded creatures and have to maintain a core body temperature around 36.2°C. As a species, our origins in Africa began towards the end of the last ice ages. It was during the end of these ice ages that our colonization of the planet began. Therefore, we have adapted to weather that is colder than our bodily needs. When it is cold, we can regulate our body temperature by getting goosebumps, shivering, increasing nutrients and exercising to stay warm. By the use of fire and erecting shelters we learned how to modify our physical environment. And we invented clothes to keep us warm. These things are all part of being human. 

As long as we can keep our bodies around 36.2°C, we function just fine. But what about at the other end of the spectrum? When ambient heat is well above our preferred core temperature? At 38°C, our bodies don’t feel so good anymore and by 40°C, death is a likely outcome. Too much heat raises our heart rate, which makes blood circulation increase, dilating blood vessels in the skin. These physiological mechanisms help the body lose body heat. And we can sweat, but this only really works in dry heat, like in a desert. When the temperature is hot and humid, sweating doesn’t help that much. This is because when sweat leaves your skin, it can’t diffuse into the surrounding air, which is also saturated with moisture. When you sweat in humid heat, your skin feels moist and sticky, but you do not feel any cooler.


Hot temperatures activate the hypothalamus, which is the part of the brain that is responsible for thermoregulation.  Interestingly, the hypothalamus is also linked to the regulation of emotions. Neurotransmitters and hormones involved in thermoregulation can therefore impact your emotional state. For instance, more adrenaline is produced in hot weather whereas more serotonin is produced in cold weather. Adrenalin is known to encourage aggressive behavior whereas serotonin suppresses aggression. 

An experiment was done to empirically test whether heat has a bearing on the well-being of people. A random sample of people were assigned to sit in an uncomfortably hot room for an extended period of time whilst another group sat in a cooler, more comfortable room. Researchers found that the people exposed to heat were more likely to show aggressive tendencies than the others.

But we hardly need science to tell us this. People have always known hot weather causes hot tempers. Our language is littered with idioms such as “Hot under the collar”, “Hot and bothered”, “Saw red”, “His/her blood boiled”, “In the heat of the moment” and” Tempers flared”. Our language developed around the inevitability that hot equals angry, or at least grumpy! 

Humans can acclimatize to heat after 5 or 6 weeks of constant exposure, but if the temperature rapidly rises 10°C and remains that high for an extended period of time, such as in a heatwave, then acclimatization is not possible. As the temperature continues to rise, the hypothalamus causes the body to decrease thyroid stimulating hormones, slowing the metabolic rate and triggering lethargy. We now do have the technology to regulate the temperature of our homes to a comfortable level using air conditioning. Air conditioners are unfortunately a catch-22 solution. They keep us cooler but increase the production of greenhouse gases into the atmosphere. 

So, let’s try to break down how climate change may affect the man in the street. The problem runs deeper than just getting hot and bothered and needing to quickly find a swimming pool and an ice-cold beer. 


I guess one way a lot of us have experienced the effect of hot weather on our mood is on the road. Think about how many road rage incidents are reported in hot months compared to when everyone is cooler and more level-headed. This is almost anecdotal, but let’s see if science has proof: A study was done at the University of Arizona to assess the effects of rising ambient temperature and horn honking in traffic. It was found that as the temperature increased, horns were honked much more than in cooler weather, and the horns that got honked the most belonged to cars without air-conditioning!

Back to our idioms, People from warmer countries are often accused of being “hot-headed”.  There is a temperature-aggression hypothesis that predicts that people experiencing more hot days exhibit more aggressive behavior than the good citizens of colder climes.


Studying the temperature-aggression hypothesis has led to the emergence of a model that predicts aggressive behavior, called the General Aggression Model. This model is built on the assumption that the relationship between heat and aggression will cause increasing assault cases and violent crimes during hot periods of time. For example, when it is hotter, more aggressive crimes such as homicide, assault or rape are likely to occur. Even school children are found to get more aggressive and have more fights during the heat.


Another model called the Routine Activities Theory, suggests a more indirect relationship between heat and violent behavior. When the weather is warm, people spend more time outdoors. This makes it easier for criminals to share the same spaces as potential victims, resulting in more opportunistic incidents of assault and robbery. 

Regrettably, the poorest of people are often the most vulnerable to this phenomenon. The city of St. Louis, USA is generally considered to be poorer than most American cities, and with a higher crime rate. Often the life style of poor, inner city dwellers involves events taking place out on the streets. A study done in this city has shown that each time the temperature rose by one degree, the average monthly crime rate increased by 1%. This study also showed that 20% of the poorest communities will amount for more than 50% of the predicted climate-related increases in violent crime. 


The link between aggression and violent crime is not just a generalized concept. In an article titled “A Rise in Murder? Let’s Talk About the Weather”, New Your Times contributor Jeff Asher suggests that there could even be a correlation between heat, gun violence and murder incidents in American cities. For years crime analysts have battled to ensure that their statistics are accurate because crime victims often fail to report the incident to the police. There are a host of reasons for this including intimidation, fear of the police or simply apathy on the part of the victim. The murder rate is however different, there is a body that can be definitively counted. 

Asher notes that the murder rate in the USA rose in 2015 and 2016. He then shows correlations in 10 cities between increased temperature and shootings in this time period. He also refers to the increase in outdoor activity during hot periods. The article emphasizes the need for better research into the link between gun violence and fluctuations in the weather.  


The Intergovernmental Panel on Climate Change (IPCC) has developed a number of climate models to stimulate the different ways in which the dynamics between the most important drivers of climate (atmosphere, oceans, land surfaces and ice) will change in future.  These changes will depend on variations of the amount of the sun’s energy reaching Earth, changes in the reflectivity of the Earth’s atmosphere and surface, and changes in the greenhouse effect.  One of the models, called A1B, predicts a scenario that assumes the world of the future will have rapid economic growth, low population growth and a rapid replacement of fossil fuels with new energy-efficient technology. And yet, with this euphemistic outlook, it is predicted that global temperatures are still likely to rise by about 2.8°C (5 °F) by the year 2099. 

Climate scientists have issued a dire warning that global temperature must be kept below a 2°C rise or else we must prepare for calamitous consequences. In his paper Crime, Weather and Climate Change Matthew Ranson of the Harvard Kennedy School, uses historical crime records with the IPCC A1B model and predicts that the USA will experience additional 35 000 murders, 216 000 rapes, 1.6 million aggravated assaults, 2.4 million simple assaults, 409 000 robberies, 3.1 million burglaries, 3.8 million cases of larceny and 1.4 million cases of vehicle theft than what would have occurred between 2010 and 2099 if there was no climate change.

 Anyone living in the developing world will skeptically describe this utopian scenario as overly optimistic. Those living in the developing world will probably feel that one of the IPCC A2 models are more fitting with reality. These story lines, referred to as “Business as Usual” scenarios, predict that economic growth will be slower and more unevenly spread in different parts of the world; population growth will continue to rise unchecked and technological change to cleaner energy sources will be fragmented regionally. Under these conditions we can expect a 3.2°C rise in global temperature by the turn of the century.

An example of a country whose citizens are more likely to agree with the IPCC A2 models is South Africa. Here is a country with much of the population living in extreme poverty without much hope of ever getting a job. To ward off starvation, crime becomes a more attractive option. And keeping warm in winter means huddling around burning tires on street corners. warmth takes priority over burning fossil fuels, and hunger takes priority over whether more crime is committed in hot or cold weather. 


A study was conducted in Tshwane, the capital city of South Africa, to see whether high temperatures or high rainfall increased certain types of crime in various parts of the city. Results show that there is an undeniably an increase in crime in hotter temperatures. In fact, violent crimes increased by 50%, sexual crimes by 41% and property crimes by 21% on hot days compared to cold days. Violent and sexual crimes can be explained mostly by the temperature-aggression hypothesis, whereby hot temperatures increase the level of frustration and aggression in individuals. The increase in property crime can be explained by the Routine Activities Theory, where people are more likely to leave their homes in hot weather to enjoy outdoor events, thus leaving their property less protected from crime incidents. Interestingly heavy rainfall decreased the incidents of violent and sexual crimes but slightly increased property crime by 2%. Perhaps this is because rainy weather gives more concealment for the criminal to pass unnoticed. 


I am not an expert in the field of crime and security. I am an ecologist with a keen interest in the crime of global warming. It’s evident that climate change is going to have an impact on crime levels. This will impact on the personal safety of politicians, ecologists, account executives, nursery school teachers, street sweepers, parents and grandchildren alike. Clearly reduce, reuse, recycle isn’t going to address the situation when an enraged primate in a leather jacket is trying to smash through your car’s passenger window. Here are a few practical considerations that could be implemented:

  • Consciously activate your situational awareness during hot temperature situations, specifically when in crowds of people. The hotter it gets the more space you are going to need to escape. If you don’t know to do that you can learn situational awareness in this article – Getting practical with self awareness.
  • Notice how your temper fluctuates in the heat. When this takes place, increase your exposure to fresh air and shade, change your breathing patterns and drink lots of water. Also do not exert yourself physically in the heat.
  • Neighborhood watches and local police departments should be planning patrol routines around specific weather conditions. Hot nights when there are lots of people on the street will require increased patrols or extra manpower on the ground. 

I have focused on the direct effects of climate change, heat and human behavior. In my next post, I will explore the relationship between crime and violence, and climatic disasters like the fallout from floods, wildfires, tornadoes, hurricanes and cyclones. 

References & further reading 

al, V. L. (2017). Aggression and violence around the world: A model of Climate, Aggression, and Self-control in Humans (CLASH). Behavioral and Brain Sciences, 1-58.

al., A. C. (2000). Temperature and Aggression. Advances in Experimental Social Psychology, 63-133.

Anderson, C. A., & Anderson, K. B. (1998, December). Temperature and Aggression. Retrieved from Research Gate:

Anonymous. (n.d.). Temperature. Retrieved from Earth in the Future:

Asher, J. (2018, September, 18). A Rise in Murder? Lets Talk About the Weather Retrieved from The New York Times:

D, S. F. (2018). The influence of extreme weather conditions on the magnitude and spatial distribution of crime in Tshwane (2001–2006). South African Geographical Journal Volume 100 – Issue 3.

Hanna, L. (2013, January 10). Could we acclimatize to the hotter summers to come? Retrieved from The Conversation:

Intergovernmental Panel on Climate Change (IPCC). (2000). Emissions Scenarios. Retrieved from IPCC:

Mares, D. (2013, February). Climate Change and Levels of Violence in Socially Disadvantaged Neighborhood Groups. Retrieved from Researcg Gate:

Matthew, R. (2012, November 10). Crime, Weather and Climate Change. Retrieved from

Nakicenovic, N., & Swart, R. (2000). Special Report on Emissions Scenarios. A Special Report of Working Group III of the Intergovernmental Panel on Climate Change. UK: Cambridge University Press.

O’Niel, D. (2012). Adapting to Climate Extremes. Retrieved from

Plante, C., Allen, J. J., & Anderson, C. A. (2017, April). Effects of Rapid Climate Change on Violence and Conflict . Retrieved from Oxford Research Encyclopedias Climate Science:

Richerson, P. J., & Boyd, R. (1998, January). The Pleistocene and the origins of human culture: Built for speed. Retrieved from ResearchGate:

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