Abstract:
This study used the RClimDex software to examine trends in extreme air temperature and rainfall in the Black Volta
River Basin (BVRB) for the present (1981–2010) and future 2051–2080 (late twenty-first century) horizons. The
analysis of the future extreme events was conducted using data output of four ensemble models for two IPCC
emission scenarios, Representative Concentration Pathways (RCPs) 4.5 and 8.5. A bias correction method, the
quantile-quantile (Q-Q) transformation technique, was applied to all the modelled temperature and rainfall data set
prior to the index calculation. The results of analysis of the present-day climate indicate warming and wetting of the
BVRB. Increasing trends were seen in the extreme warm indices while the extreme cold indices showed mostly
decreasing trends. Majority of the trends observed in the indices were statistically significant (95% confidence level).
The extremes in rainfall also showed increasing trends in amounts and intensity of rainfall events (majority of
increasing trends were statistically insignificant). Projected temperatures for the late twenty-first century showed
decreasing and increasing trends in the cold and warm indices respectively, suggesting warming during the period.
Trend analysis of future rainfall projections mostly showed a mix of positive and negative trends offering no clear
indication of the direction of change in majority of the extreme rainfall indices. An increase in extremely wet day
events is however projected for the period. The results from this study could inform climate change adaptation
strategies targeted at reducing vulnerability and building resilience to extreme weather events in the BVRB.
