Temperature trends for coastal and adjacent higher lying interior regions of KwaZulu-Natal, South Africa

Abstract

Temperature trends for KwaZulu-Natal (KZN), South Africa, are investigated for the period 1930–2015, with the intention to test whether interior regions (within ~ 100 km of the coast) are warming faster than coastal regions, given oceanic moderating effects along the coast. This is achieved through analyzing instrumental temperature records from the coastal station of Mount Edgecombe, and adjacent interior stations of Cedara and Emerald Dale. The modified Mann-Kendall test is used to determine annual and seasonal mean temperature ( $$ \overline{T} $$ ), maximum temperature (Tmax), and minimum temperature (Tmin) trends for the period 1930–2015, and for the most recent few decades. For annual Tmax, a significant increasing trend (0.07 °C/decade) is recorded at the coast, whereas adjacent interior stations record no trend. Annual Tmin record significant warming at all stations, with warming rates over the interior being double that recorded at the coast for the period 1930–2015. For seasonal Tmin over the interior, significant warming rates are recorded: 0.21 °C/decade (summer), 0.22 °C/decade (autumn), 0.20 °C/decade (winter), and 0.15 °C/decade (spring). Seasonal Tmin warming over the coast were also significant: 0.16 °C/decade (summer), 0.08 °C/decade (autumn), 0.06 °C/decade (winter), and 0.12 °C/decade (spring). Thus, higher lying interior regions are warming at considerably greater magnitudes compared to adjacent coastal areas, mainly due to Tmin warming trends. For the period 1930–2015, record positive annual Tmax anomalies are reported for 2015 at Mount Edgecombe (mean anomaly = 1.6 °C), Cedara (mean anomaly = 1.7 °C), and Emerald Dale (mean anomaly = 2.0 °C).