Surface temperature trends from homogenized time series in South Africa : 1931-2015

Abstract

Previous assessments of historical trends of measured surface temperature in South Africa have all shown a general upward trend, in both mean and extreme values, over recent decades. In addition, some regional differences in trends have been identified. Most of these studies focused on the period from about 1961 up to the last year that could be included before publication, as only climate stations situated in the same position for the entire analysis period were analysed. A data homogenisation procedure enabled the combination of time series of stations from which trend analysis could be applied, extending the common analysis period for this study back to around 1931. The trend results, based on the WMO ETCCDI indices, continue to show the general warming trend shown in previous analyses, with a general increase in extreme warm events, and a general decrease in extreme cold events across South Africa. The analysis of seasonal trends show that, while there are noteworthy differences on a regional basis, austral summer shows on average the strongest warming, followed by autumn, winter and spring. The central interior, which exhibited significant cooling in previous analyses, now shows non-significant or similar trends when compared to the other parts of South Africa. There is no countrywide acceleration in the warming trends, but some regional consistencies in the temporal changes in trends could be determined, i.e. increases in trends in the central interior and decreases in trends along most of the coastal region.