Book excerpt: Heliophysics is a fast-developing scientific discipline that integrates studies of the Sun's variability, the surrounding heliosphere, and the environment and climate of planets. Over the past few centuries, our understanding of how the Sun drives space weather and climate on the Earth and other planets has advanced at an ever increasing rate. This 2010 volume, the last in this series of three heliophysics texts, focuses on long-term variability from the Sun's decade-long sunspot cycle and considers the evolution of the planetary system over ten billion years from a climatological perspective. Topics covered range from the dynamo action of stars and planets to processes in the Earth's troposphere, ionosphere, and magnetosphere and their effects on planetary climate and habitability. Supplemented by online teaching materials, it can be used as a textbook for courses or as a foundational reference for researchers in fields from astrophysics and plasma physics to planetary and climate science.