Projected temperature increases over northern Ghana

Abstract

This study reports on projected temperature increases and their likely implication on smallholder farming systems across the northern regions of Ghana. Aggregated climate data from 1961 to 2000 show that the mean annual temperature across Ghana rose by 1.0 ℃, with the greatest rate of change in the northern–eastern part of the country. For the development of the downscaled climate projection, five regional climate models (RCMs) forced with three global climate models (GCMs) were used from CORDEX and CMIP5, respectively. Eight stations spatially spread across the study locations were selected for the study based on the quality and completeness of data. The study used daily, minimum and maximum temperature station data from 1980 to 2014 obtained from the Ghana Meteorological Agency. The downscaling was done for the emission scenarios pathways—Representative Concentration Pathways (RCP) 2.6 and 8.5—from the selected RCMs using the station data. Time series of minimum and maximum temperatures averaged for the eight stations was analysed from 1961 to 2080. Results indicate temperatures are likely to increase over northern Ghana with minimum air temperature increasing by 0.5 °C under RCP 2.6 and 2.5 °C under RCP 8.5. Maximum air temperatures are likely to increase by 1 °C under RCP 2.6 and 2 °C under RCP 8.5 by the year 2080. Warming rates per year for the stations reveal that minimum temperatures are warming faster than maximum temperatures. The 99th percentile, which is a measure of heat waves, shows a close relationship between the minimum temperatures for the RCP 2.6 and RCP 8.5 pathways in all the stations except for Wenchi and Bolgatanga. Each pathway has a variation between 22.5 °C and 30 °C. The lowest projected value of the 99th percentile maximum temperature is 35 °C in Wenchi, and the highest projected is above 43 °C in Navrongo. Smallholder food crop farming systems are likely to be negatively impacted, with direct risks of low crop yield unless measures like irrigation and careful crop selection are implemented.