Trend analysis of cold extremes in South Africa: 1960-2016

Extreme cold events (cold waves) have disastrous impacts on ecosystem and human health. Evidence shows that these events will still occur under current increasing mean temperatures. Little research has been done on extreme cold events, especially in developing countries such as South Africa. These events pose a significant threat due to the low adaptive capacity, urgent development needs and relatively inadequate infrastructure in South Africa. This study presents annual and seasonal, spatial and temporal trend analyses of extreme cold temperature events for the period 1960-2016. We apply the World Meteorological Organisation Commission for Climatology and Indices Expert Team on Sector-Specific Climate Indices (ET-SCI) to South Africa for the first time, with comparison to the World Meteorological Organisation Expert Team on Climate Change Detection (ETCCDI) indices previously used in South Africa. The extreme cold indices are calculated using the RClimDex and ClimPACT, respectively. Trends were calculated using the non-parametric Mann-Kendall test, Spearman Rank Correlation Coefficient and Sen's slope estimates. A decreasing trend is found for annual cold spell duration and cold wave frequency, at rates of 0.10 days.day(-1) and 0.02 events.day(-1), respectively. Seasonally, coldest day temperatures increased in autumn, with increases of 0.02 degrees C.day(-1) for the period 1960-2016. Regionally, increasing trends in annual cold spell duration days were evident in stations located in the Western Cape, Eastern Cape, North-West Province, at a rate of 0.03 days.day(-1). Increasing trends in cold waves were observed for stations in Northern Cape, Gauteng, KwaZulu-Natal and the Eastern Cape Province, at a rate of 0.01 events.day(-1). These results contribute to the awareness and recognition of the incidence and duration of cold extreme events in South Africa, seeing that studies suggest that anomalously cold events may persist in a warming world.

Automated summary

This study analyzed extreme cold events in South Africa from 1960 to 2016, finding decreasing trends in the duration and frequency of cold spells, but an increase in the coldest day temperatures in autumn. Regional differences were also observed in cold wave trends across different provinces in South Africa, highlighting the potential socio-economic impacts of persistent cold extreme events in the region.