Earth’s climate results from an array of interacting processes. We study the atmospheric circulation, chemistry, and water cycle; the physics, biology, and reservoirs of heat and carbon in the world’s oceans; and how the oceans and atmosphere interact with the frozen, icy parts of the earth and other planets. We use models, observations, and many other tools to investigate fundamental processes and interactions among these systems on timescales from seconds to geological. Through this work, we develop new understanding of how these systems vary naturally on Earth and other planets, and predict how they will change in the future through human activities.