This lecture covers the Earth's energy balance, focusing on topics such as radiation, greenhouse gases, and aerosols. It explains concepts like blackbody radiation, Stefan-Boltzmann law, solar constant, and the transfer of solar radiation through the atmosphere. The lecture also delves into the absorption and interaction of radiation with atmospheric constituents, the greenhouse effect, and the influence of aerosols on climate. Various types of aerosols, their sources, sizes, and atmospheric lifetimes are discussed, along with their impact on Earth's climate system.