Cosmic rays are energetic particles originated from sources outside the Earth. Recently, there is a growing interest in studying the relationship between cosmic rays and climate, particularly under the context of global warming. This book provides a concise introduction on the topics at a level appropriate to graduate students and researchers. In this book, plasma physics, solar physics, cosmic rays physics as well as atmospheric physics are introduced. The historical relationship between the solar activity and climate as well as the recently observed relationship between cosmic rays and cloud formation are presented. The meteorological effects on cosmic rays and the measurements of atmospheric temperature profile by cosmic rays with its potential application to weather forecasting are discussed.