Over the past few decades there has been a growing interest in investigating the link between weather and various types of crimes. However, most research in this area has produced inconsistent and often paradoxical results. For instance, a few studies have found no apparent seasonal fluctuations in crime. Others have found a rise in crimes during either colder winter months or warmer summer months. However, very little is known about how the amplitude and spatial distribution of criminal activity in South Africa is affected by climatic conditions. A study was performed to determine a link between criminal activity and climate in the country's capital city known as Tshwane. The aim was to investigate whether there was any correlation between the frequency in crime rate and extreme weather conditions, using temperature and rainfall as proxy. In other words: do extremely hot days or high-rainfall days experience higher or lower rates of violent, property or sexual crime? The spatial distribution of different crime types and extreme weather events were also analysed. Simply put, does crime occur in different places on extremely cold days than it does on really hot ones?
The results suggest a strong association between temperature and criminal activity, with an increase in crime rate in step with a temperature rise. There’s a less significant association between rainfall and crime. The spatial distributions of all types of crime are found to differ significantly depending on the type of weather extreme observed. These results could help law enforcement agencies better understand how weather affects crime patterns in South Africa’s urban areas and develop and implement appropriate crime prevention measures.
The notion that there’s a relationship between criminal activity and climate is nothing new. Over a century ago, Belgian sociologist and scholar Adolphe Quételet observed that crimes against people reach a maximum during the warmer summer months, while crimes against property reached a peak during winter. Later, he developed the temperature-aggression theory, which provides a psychological explanation for the increase in crime during warmer months. It suggests that warmer temperatures will lead to an increase in an individual’s frustration and discomfort levels and so increase the likelihood of aggression. This could in turn result in interpersonal crimes such as assault.
In the case of the Tshwane study, statistical analysis was performed to find any relationship between extreme weather conditions and crime in the nation’s capital. Climate data for the city was obtained from the South African Weather Service over a 5-year period from September 2001 to the end of August 2006. Daily average temperatures were computed before extracting the ten hottest for each year of the five years resulting in a dataset of 50 days. The process was repeated for low-temperature days, high-rainfall days, no-rainfall days and random-rainfall days.
Crime data for the same period were also retrieved from the South African Police Services’ Crime and Information Analysis Centre. The data included the geographical location of each crime; the date and time of day that each crime was committed; and the specific type of crime committed. A total of 1,361,220 crimes were reported in the five-year period across 32 different categories. All crime was then categorised into either violent, sexual or property crimes before calculating a count of crime per type per day. Next, a recently developed method called the spatial point pattern test was used to determine whether the spatial distribution of crime on the three types of days (very hot, very cold and rainy) changes. That is, does the spatial patterning of crime in Tshwane change depending on certain rainfall and temperature conditions? The findings demonstrate that the amount of violent, sexual and property crime in the city of Tshwane is significantly affected by temperature and, to a lesser extent, rainfall.
The magnitude of violent, sexual and property crime was higher on hot days compared to cold or random temperature days. Violent crimes increased by 50% on hot days compared to very cold days. Sexual crimes increased by 41% and property crime by 12%. Violent and sexual crimes in Tshwane also decreased on high-rainfall days. Surprisingly, property crime was found to increase slightly on heavy rainfall days, though only by 2%. Second, the spatial distribution of violent and property crime was found to differ on days by temperature and rainfall. There is a considerable change in the way that particularly violent and property crime is spatially distributed in Tshwane depending on the weather conditions. More research is needed to confirm these findings and to determine if the results can be generalised to other urban areas in South Africa.
Our findings can be used to identify communities that are more prone to crime under certain meteorological conditions and allow stakeholders to target these neighbourhoods and plan interventions. It also allows stakeholders to adequately develop and implement suitable intervention practices in similar at-risk neighbourhoods. For the police and others responsible for specifically addressing long-term solutions to crime, crime pattern analysis can utilise the understanding of how weather events influence crime patterning and provide measures to take appropriate action.
Breetzke, G. (2018, August 7). When temperatures rise, so do crime rates: evidence from South Africa. The Conversation. Retrieved August 31, 2018, from https://theconversation.com/when-temperatures-rise-so-do-crime-rates-evidence-from-south-africa-100850
Melusine Thieme, E. (2017, July 13). Johannesburg. Living in the world’s most dangerous city. Good Things Guy. Retrieved August 31, 2018, from https://www.goodthingsguy.com/opinion/johannesburg-living-worlds-dangerous-city/
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© 2018 Oceanographer Daneeja Mawren
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