This first glance at the whole Earth System and how it determines the state of the global climate should give you a good sense its complexity and some of the important interconnections. You might also begin to see that the operation of the system involves several cycles (carbon cycle, water cycle, etc.), which are systems that are more or less closed. In these cycles, material passes from place to place in a cyclical fashion. If you track a particular water molecule over millions of years, you may see it move from the atmosphere to the land to the oceans to the deep interior, then up through a volcano to the atmosphere. Many of these cycles represent important subsystems of the global climate system, and we will explore these cycles throughout this book.

5/12