This book describes the interaction of the main biogeochemical cycles of the Earth and the physics of climate. It takes the perspective of Earth as an integrated system and provides examples of both changes in the current climate and those in the geological past. The first three chapters offer a general introduction to the context of the book, outlining the climate system as a complex interplay between biogeochemistry and physics and describing the tools available for understanding climate: observations and models. These chapters describe the basics of the system, the rates and magnitudes and the crucial aspects of biogeochemical cycles needed to understand their functioning. The second part of the book consists of four chapters that describe the physics required to understand the interaction of the climate with biogeochemistry and change. These chapters describe the physics of radiation, and that of the atmosphere, ocean circulation and thermodynamics. The interaction of aerosols with radiation and clouds is addressed in an additional chapter. The third part of the book deals with Earth’s (bio)geochemical cycles. These chapters focus on the stocks and fluxes of the main reservoirs of Earth’s biogeochemical cycles—atmosphere, land and ocean—and their role in the cycles of carbon, oxygen, nitrogen, iron, phosphorus, oxygen, sulphur and water, as well as their interactions with climate. The final two chapters describe possible mitigation and adaptation actions, in relation to recent climate agreements, but always with an emphasis on the biogeochemical aspects.