Projection of temperature in Java Island in 2021 – 2050 based on conformal cubic atmospheric model

Climate change is an essential issue in the world. One of the indicators of this is an increase in average surface temperature. Indonesia experienced an increase in temperature ranging from 0.2-0.3 °C every decade. This increasing temperature impacts human life in all aspects. Therefore, it is necessary to project future temperatures so that mitigation measures can be carried out appropriately. In this study, projections of surface temperatures on the island of Java in 2021-2050 have been carried out by downscaled Global Climate Model (GCM) using dynamical downscaling by CCAM model with the RCP 4.5 scenario. This output has 27 km spatial resolution and daily temporal resolution. Before the projection, the CCAM data output was corrected for bias using the linear scaling method. The calculation results show that the corrected data can improve the model's performance by reducing the RMSE value by about 6 degrees. However, statistical calculating (minimum, maximum, mean, 5th percentile, 95th percentile, and variance) showed that the model output was overestimated compared to the observation data. In the temperature projection for 2021-2050, it was found that 79.04% of Java Island experienced an increase in maximum temperature, reaching 4.49 ^oC. 99.05% of Java Island experienced a decrease in minimum temperature evenly to -8.51 ^oC in the eastern part of Java Island. 75.05% of Java area experienced a decrease extreme low temperatures up to –7.32 ^oC on the east side of Java, while an increase in extreme temperatures occurred in 65.71% of the island of Java. The increase in extreme temperatures reaches up to 3.04 ^oC on the northeast side of Java Island.