Exploring shifts in the threshold for reporting on extreme temperature events over the past century in South Africa

Abstract

This research aims to better understand how the heat wave threshold has changed in South Africa over the past century. Based in practices of historical climatology, a mixed methods approach was used to explore both purely quantitative meteorological data and more documentary evidence from archival newspapers, namely the Rand Daily Mail and the Business Day between the years 1903-2023. By exploring both sides of heat waves, the meteorological data as well as human perception around heat waves, this study aimed to explore how heat waves and their perception by people in South Africa have changed over time. This study identified 235 heat waves across 12 locations throughout South Africa that were reported in newspapers and had coinciding SAWS meteorological data. The newspaper reports were used to explore how people and journalists perceive high temperatures and write and talk about heat waves. Over the course of the last century, newspaper reported heat wave thresholds have not changed in any statistically significant way. This has implications as climate change causes a shift towards warmer mean annual temperatures and an increase in extremely hot days, meaning that there will be more days above this perceived threshold where people in South Africa will be more vulnerable to thermal stress. A total of 395 heat waves that align with the SAWS heat wave definition were also explored, also showing no statistically significant change over time. This exploratory study of historical heat waves across a range of locations in South Africa demonstrates the richness of documentary evidence of climate and weather changes through newspaper reporting. It also explores the ways in which people have always had an interest in the weather and climatic changes and why they are happening. In a warming world where heat waves will increase in intensity, understanding how they are changing and whether human understanding of them is changing too will be crucial to public health preparedness in South Africa.