he global change studies in the United States are mainly supported by the U.S. Global Change Research Program (USGCRP). The four key global change issues of USGCRP are seasonal to interannual climate variability, climate change over decades to centuries, changes in ozone, UV radiation and atmospheric chemistry, changes in land cover and in terrestrial and aquatic ecosystems. At the current stage, water vapor and cloud remain to be the emphasis of global change research due to the great uncertainties in this aspect. Another focus is the detection and attribution of climate changes. The climate modeling keeps to be one of the main methodologies of global change studies. The application of satellite based observational data in global change studies has been made great progresses. In the coming years, the new research focuses of global change studies in the United States will be climate modeling, short term climate prediction, climate changes over decades to centuries, changes in ozone, UV radiation and atmospheric chemistry, changes in land cover, and in terrestrial and aquatic ecosystems, regional-scale estimates of global change, application of satellite data and national assessment of the consequences of climate change for the United States.