Climate trends in southern Africa

The observed and projected changes in the climate of southern Africa in the period 1900-2100 were analysed. Ten observed, reanalysed and model-simulated climate data sets were explored for changes in surface air temperature, rainfall, air pressure, winds, ocean currents and sea surface height. The analysis of spatial and temporal climate trends from historical observations provided a context to assess two coupled model simulations (IPSL, MIROC) based on the A1B emission scenario. Temperatures in the satellite era exhibited upward trends greater than +0.4 degrees C/year in the MIROC and IPSL A1B model simulations; between +0.02 degrees C/year and +0.03 degrees C/year in NCDC, HADCRU, CFS-R and NCEPe data sets; +0.01 degrees C/year in NCEPr and GHCN observations; and +0.002 degrees C/year in the ECMWF data set. Although rainfall trends in the satellite era were minimal in many data sets because of drought in the early 1980s, there was a significant downtrend in the IPSL simulation of -0.013 mm/day per year. When averaging the longer data sets together over the 20th century, the southern African rainfall trend was -0.003 mm/day per year. Other key features of the analyses include a poleward drift of the sub-tropical anticyclones and a +1.5 mm/year rise in sea surface height along the coast.