Climate variability and change refer to long-term shifts in temperatures and weather patterns, driven by complex interactions within the Earth system. These changes occur through natural orbital cycles, fluctuations in solar energy output, and alterations in atmospheric composition, such as the concentrations of greenhouse gases. The energy balance of the planet is regulated by the differential absorption and re-emission of radiation, a process which dictates global temperature trends. Variability manifests across various timescales, from interannual shifts caused by ocean circulation patterns to multi-millennial changes related to plate tectonics and ice sheet growth. Understanding these mechanisms requires modeling the exchange of energy and matter between the atmosphere, hydrosphere, lithosphere, and biosphere to predict the range of potential future states.