Future Changes of Temperature and Precipitation in Java Island Based On NEXGDDP-CMIP6 Models

The complex interactions between monsoon circulation, ocean-atmosphere variability, and steep topography over Java require high-resolution climate projections to accurately assess future warming and precipitation changes. This study uses eight downscaled NEX-GDDP-CMIP6 models, evaluated against the SA-OBS dataset for the period 1984–2014, to assess historical performance and quantify projected changes in SSP2-4.5 and SSP5-8.5. The models perform well with a rainfall correlation of r = 0.68–0.75 (RMSE 77–84 mm/month) and a temperature correlation of r = 0.40–0.70 (RMSE 1.1–1.3°C), although they exhibit a bias towards the rainy season of +28–35 mm/month and a bias towards warm temperatures of +1–3.5°C. Forward projections indicate warming of +0.8–1.4°C (SSP2-4.5) and +1.5–2.3°C (SSP5-8.5), with the most significant increases in the northern and eastern lowlands. Precipitation changes range from -3% to +7% in SSP2-4.5 and from 0% to +12% in SSP5-8.5, while the DJF season is expected to be wetter by 5–15% and the JJA season is likely to be drier in East Java.