How the weather impacts crime

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South Africa is known around the world for its sunny skies, natural beauty – and its crime rate. A few years ago, we became notorious for having a higher murder rate than the (then) active war zone in Afghanistan, and the number of robberies, cash-in-transit heists and other violent crimes has continued to remain high.

How the weather impacts crimeDespite this, there is very little local research into the contributing factors that have resulted in the country’s excessively high crime rate. Poverty and unemployment are, of course, two of the leading causes of gangsterism and crime in South Africa, but various other influences also have a role to play.

One of these, according to new research, is the weather. Professor Gregory Breetzke from the Department of Geography, Geoinformatics and Meteorology at the University of Pretoria set out to determine whether there is an association between criminal activity and climate in Tshwane. His research looked at whether extremely hot or high-rainfall days experienced higher or lower rates of violent, property or sexual crime.

The results were surprising for anybody who thought that a heat wave made everyone – including criminals – more lethargic. Beetzke found that there is a strong association between temperature and criminal activity. That is, as the temperature goes up, so too, does crime. There’s a less significant association between rainfall and crime, the research found. In fact, the ‘spatial distributions’ of all types of crime are found to differ significantly depending on the type of weather extreme observed.

The magnitude of violent, sexual and property crimes 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 crimes 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%.

The study used climate data for the city from the South African Weather Service for a five-year period, from September 2001 to the end of August 2006. The researchers then calculated daily average temperatures before extracting the ten hottest for each year of the five years. That provided a dataset of 50 days. The process was repeated for low-temperature days, high-rainfall days, no-rainfall days and random-rainfall days.

The researchers then used crime data from the South African Police Services’ Crime and Information Analysis Centre to flesh out the picture. The data included the geographical location of each crime; the date and time of the 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 crimes were then categorised into either violent, sexual or property crimes before a count of crimes per type per day was calculated. Finally, the research team used a recently developed spatial point pattern test to determine whether the spatial distribution of crime on the three types of days – very hot, very cold and rainy – changed.

“The results of this research have the potential to inform how law enforcement agencies and other relevant stakeholders tackle crime 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. The findings also allow 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 says.

Whether this research will help the over-stretched law enforcement agencies of the country remains to be seen. Ordinary people, however, can sleep a little more soundly when they hear the rain start, and now know to be more wary when the temperatures soar.

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Crown Publications, one of South Africa’s largest business-to-business publishing houses, came into existence in 1986. Since then, the company has grown from producing a single magazine, Electricity SA (renamed Electricity+Control), to publishing six monthly magazines, three quarterlies, and a number of engineering handbooks.