A new perspective on future precipitation changes in Tanzania

Abstract Tanzania's population and economy is very vulnerable to precipitation changes and extremes and therefor it is highly relevant to give reliable information about future precipitation changes for suitable adaptation planning. However, there is a strong disagreement between climate models for future precipitation changes in the region, which limits local trust in the projections. We break down the assessment of precipitation changes by classifying different precipitation categories using the Standardized Precipitation Index (SPI). With this novel approach, we analyse the projections from the CORDEX Africa Ensemble and find that despite the disagreement in the trend of total precipitation, most models project a robust decrease in “normal” conditions as well as a robust increase in both extreme wet and extreme dry conditions throughout the 21st century. The differences between the models in terms of total precipitation are related to shifts of (near) normal conditions to wetter conditions in the case of wet models and to drier conditions for dry models. The results indicate an overall broadening of the rainfall distribution especially toward extremely wet conditions. Such robust results can contribute to build trust in climate projections for adaptation planning.