Abstract
Time series of South African temperatures were investigated for temporal and spatial trends for the period 1960 to 2003. For this purpose a total of 26 climate stations were utilized, with each having sufficient data available and not having undergone major moves or changes in exposure that would influence the homogeneity of their data series. The vast majority, a total of 23 stations, showed positive trends in their annual mean maximum temperature series, 13 of them significant, with trends higher for central stations than those closer to the coast. Annual mean minimum temperatures showed 21 stations having positive trends, with 18 significant. Stations not showing significantly positive trends in annual mean minimum temperatures were mostly situated in the central interior. The annual average temperature data series of 24 of the stations showed positive trends, with 18 of them significant. Trends of mean seasonal temperature showed that temperature trends are not consistent throughout the year, with the average trend for autumn showing a maximum and spring a minimum. Monthly trends of average annual temperatures showed large differences in trend between stations, and for each station between months, but similar tendencies in trend between months were found to exist for stations close by and also for groups of stations on a regional basis. Trends in diurnal temperature range are almost equally divided between positive and negative, with the positive trends in the central interior mainly being caused by large positive trends in maximum temperature. It is also shown that, in general, days and nights with relatively high temperatures have increased, while days and nights with relatively low temperatures have decreased. The effects of urbanization on temperature trends are investigated, and the conclusion is that most stations regarded as urban stations are still useful for trend analysis; being situated on the outskirts of cities they are, therefore, not substantially influenced by the urban heat island. El Niño and La Niña events do not seem to play a significant role in the increasing temperatures observed. Copyright © 2004 Royal Meteorological Society