This project was started under the GEOSS/Asian Water Cycle Initiative (AWCI) framework to analyse historical climate and hydrology trends with future climate change impact assessment. The result of Mann-Kendall test shows an increasing trend in temperature, with decreasing trends in precipitation and runoff. Temperature in most regions increased. However, similar to runoff, precipitation over 30 years in Asia decreased. To analyse future climate change impact, three GCMs (CGCM2_3_2, CGCM3_T47, and CM4) were selected according to the results of the probabilistic uncertainty analysis, correlation coefficient, and RMSE. Temperature was expected to increase in all regions. Precipitation increased in most regions except central Asia in all seasons. Runoff was expected to be the same as that of precipitation. The water balance over 18 Asian basins was increasing with increasing times toward the future period. We are able to understand the trend of climate and hydrology in detail, including their future trends. The results analysed in this study will be useful in establishing future climate adaptation measures in Asia.