Evaluation of long-term changes in precipitation over Bolivia based on observations and Coupled Model Intercomparison Project models

Using observations and model simulations from the 5th and 6th phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively), this study evaluated changes in monthly, seasonal, and annual precipitation over Bolivia from 1950 to 2019. Results demonstrate that observed precipitation is characterized by strong interannual and decadal variability. However, long-term precipitation trends were not identified on the annual scale. Similarly, changes in seasonal precipitation were almost nonsignificant (p > .05) for the study period. Spatially, albeit with its complex orography, no substantial regional variations in observed precipitation trends can be identified across Bolivia. In contrast, long-term precipitation trends, based on CMIP5 and CMIP6 models, suggest a dominance of negative trends, mainly during austral winter (JJA) (-10%) and spring (SON) (-15%). These negative trends were more pronounced in the lowlands of Bolivia (-20%). Overall, these contradictory results highlight the need for validating precipitation trend outputs from model simulations, especially in areas of complex topography like Bolivia.

Automated summary

Using data from CMIP5 and CMIP6, this study assessed precipitation changes in Bolivia from 1950 to 2019 and found strong interannual and decadal variability in observed precipitation. However, no long-term trends were identified on an annual scale, and changes in seasonal precipitation were insignificant. Additionally, no substantial regional variations in observed precipitation trends were found across Bolivia, contrasting with the dominance of negative trends in CMIP models, particularly in the lowlands.