Spatial estimation of future temperature changes over Africa
Climate has been changing since time immemorial. However, these long-term changes are very important because of some of the consequences to mankind. Because the changes are small ones in relation to daily experiences, many people find it difficult to perceive and accept these changes. This might cause doubts in the minds of many people in the proclaimed global warming which now occupies numerous agenda of institutions and organisations concerned with the future planning and management of our planet. The first chapters of this thesis review the theories of climate change and attempts to determine temperature change predictions specifically for Africa. This study neither proclaims nor disclaims this notion of global warming. Instead, it restricts itself to estimating the spatio-temporal patterns of temperature changes for Africa from an observational perspective. Analysis of recognised records of annual surface air temperature for numerous weather stations in Africa were obtained and used to derive models of the station temperature changes over the past four decades. These models were used to predict temperature changes up to the year 2000. The individual station predictions were used to derive spatial estimates of temperature change using the IDRISI - Geographic Information Systems (GIS) provided by the Clarke University through the International Geosphere-Biosphere Program (IGBP): Global Change Database Project (GCDP): Pilot Project for Africa. The spatial extent of temperature changes was derived using Theissen polygon approximation. The derived models of climatic temperature change for various stations indicated that 58% of the African main land will not experience temperature change greater than half of a degree(-0.45° to 0.45°C) by the year 2000. There was an even spread (52% and 48%) of the stations showing decreasing and increasing temperature trends, respectively. However, 30% of all the stations showed large increasing (0.46° to 2.45°C) temperatures, while fewer stations (12%) showed decreasing (-3.02° to -0.46°C) temperatures. The spatiai pattern of temperature changes were derived and an attempt was made to compare features of the climate with specific patterns of temperature change. The North-west and Zaire Air Boundaries, which are zones of moisture discontinuity during the month of July, were compared to regional patterns of increasing temperature trends. Attempts to relate predicted temperature changes with rainfall and monthly temperatures showed no significant correlation. Stations with short records and large cyclic variability tend to produce unstable models and the implications of these trends were discussed.
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