Surface temperature variation over Zimbabwe between 1897 and 1993

Summary

The surface temperature variation over Zimbabwe, and, Harare and Bulawayo between 1933 and 1993, and, 1897 and 1993 respectively, is investigated. For the national average two significant warm phases are identified, with a net warming of +0.3 to +0.5°C since 1933. Warming occurs in maximum temperature, whereas the mean national temperature cools. The effect of the rainfall pattern on temperature is also investigated. If warming phases coincide with drought years and the warming is confined to the rainy months only, then reduced cloudiness could be an important factor in explaining some of the warming. The first warm phase occurs during the mid-1930s to late 1940 and the second major warm phase occurred from the early 1980s onwards. For Harare, with temperature records starting before 1900, a major warming phase occurred between about 1910 and late 1920. The effect of drought on the national temperature record is evident through a strong negative association between maximum temperature anomalies and rainfall anomalies. A number of possible causes of the observed changes are discussed. The effects of urbanisation and industrialisation on temperature trends over Harare and Bulawayo are quite conspicuous. The question that remains difficult to answer is whether the observed warming trend is a result of inherent climate variability, enhanced greenhouse effect or a combination of many factors.