Phase one of the Regional Climate Model Intercomparison Project for Asia reveals the capacities of regional climate models (RCMs) for simulating the Asian monsoon climate and extreme events as well. (Mearns et al. 2001;Giorgi et al. 2001). At present, analysis of the coupled atmosphere-ocean GCM (AOGCM) simulations indicates that average biases at regional scales, when simulating present-day climate, are highly variable from region to region and across models. For example, Giorgi and Francisco (2000) find that temperature biases are typically within the range of ±4°C, but exceed ±5°C in some regions, particularly in the winter. They also find that precipitation biases are mostly between -40% and +80%, but exceed 100% in some regions. Thus, a high priority for climate research is to improve the downscaling of GCM climate change to regional scales so that potential impacts can be adequately assessed (Houghton et al. 1995(Houghton et al. , 2001 Simulating regional climate poses difficulties, such as capturing effects of forcing and circulation at the planetary, regional, and local scales, along with teleconnection effects of regional anomalies. These processes are characterized by a range of temporal variability scales and can be highly nonlinear. The East Asian summer monsoon is characterized by marked variability at seasonal, interannual, and interdecadal time scales (Fu and Zheng 1998). The uncertain timing of monsoon onset and the irregular pace of its seasonal, northward progression strongly influence water availability for agriculture and urban consumption (Tao and Chen 1987;Wu and Zhang 1998). Interannual changes, such as those linked with the ENSO cycle, affect the frequency of droughts, floods, and other weather extremes that occur during the summer monsoon (Fu and Teng 1993;Ju and Slingo 1995;Fasullo and Webster 2002). Finally, on decadal-to-century time scales, the rapidly growing economy and population of East Asia presents anthropogenic influences that may also alter monsoon behavior (Fu and Zheng 1998;Quan et al. 2003). However, coarse-resolution climate models generally fail to give satisfactory simulations of the East Asian monsoon (Lau and Yang 1996; Yu et al. 2000).To date, most studies of regional climate change over East Asia have used output of GCMs without applying any downscaling techniques (Hulme et al. 1992;Zhao and Wang 1994). However, a relatively high degree of uncertainty exists in the regional climate change information of East Asia from GCMs, which results from the scenario's construction, such as future emission variations and the GCMs' modeling of the climate responses to a given scenario. Several researchers have used RCMs for simulating the regional climate of East Asia. Many of these studies have shown that RCMs can simulate the spatial detail of monsoon climate better than GCMs (Liu et al. 1994(Liu et al. ,1996Fu et al. 1998;Lee and Suh 2000). However, multiyear simulations must be used to provide meaningful climate statistics and to identify significant model errors. Therefo...