Because of its huge heat content, ocean plays an important role in determining global and regional climate and its variability in multi-temporal scale. This short course will provide introduction of air-sea interaction in different spatio-temporal scales and understanding on climate variability that influences, for example, weather patterns globally and regionally from observation and modeling data perspectives. Moreover, I will discuss the current status of climate prediction and projection using Earth system models/regional models since ocean process and variability are a main target in prediction and projection. Additionally, an introduction of global carbon cycle will be given because ocean is the largest carbon source and sink of carbon.