Temperature and precipitation extremes in the Brazilian Legal Amazon: projections under SSP5-8.5 scenario

This study aims to investigate the projections of air temperature and precipitation climate extremes in the Brazilian Legal Amazon (BLA) through the end of the century. The Brazilian Daily Weather Gridded Data dataset is used to characterise the present climate, and 12 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), under the Shared Socioeconomic Pathways scenario SSP5-8.5, are employed to assess future changes relative to the reference period (1995–2014). Student’s t-test is employed to evaluate the robustness of the projected changes. Results show that warming is projected to persist throughout the BLA, but at a lower rate in the north-east (NE) than in other areas. In the south (S) and north-western (NW) sectors, the highest maximum temperatures will increase by an average of 7°C by the end of the century. Regarding precipitation extremes, in the NW, which is currently the wettest portion of the BLA, models project a reduction in consecutive wet days (CWDs) and an increase in the amount of daily rainfall that exceeds the 95th percentile of wet days (R95p). In the NE, by the end of the century, a 30-day increase in the total number of consecutive dry days per year (CDDs) is projected, combined with a reduction in annual rainfall of ~270 mm. In the south of the BLA, models project an increase across the entire sector, with an additional 15 days per year, along with a reduction in annual rainfall. The projected changes in precipitation exhibit strong seasonality, concentrating primarily in the transitional seasons and the beginning of the rainy season, rather than occurring uniformly throughout the year. Also, the projected warming intensifies during the dry season and austral spring, especially in the NW region. In this sense, it is observed that, in the future, the climate in the BLA will become warmer, keeping the trends observed in the present climate, as shown in other previous studies. However, rainfall patterns differ between regions: while in the NE and S the climate will become drier, in the NW, the intensity of extreme rainfall is expected to increase significantly by the end of the century.