This textbook, Climate Change Science: A Modern Synthesis, Volume I: The Physical Climate , is intended for the introductory college science student who perhaps has not had a science course since secondary or preparatory school. It is also intended to serve as a more advanced textbook for students who have had a basic science course in astronomy , geology , biology , physics , or chemistry and who want to better understand Earth ’s climate , how Earth’s climate has developed, what affects it, and how it may change in the future . However, it presumes no background in any of the sciences. Basic scienti fi c concepts are introduced and explained as they become necessary for understanding the current topic. It constitutes Volume I of a twotextbook treatment of climate change science designed for a 1-year introductory science course. This volume treats the physical aspects of climate change science and is intended for a one-semester or one-quarter introductory science course.