Energy at the Surface of the Earth: An Introduction to the Energetics of Ecosystems presents way of looking at the manner in which the biological, physical, and cultural systems that mantle the landmasses of our planet receive, transform, and give off energy, which is an essential condition of existence that takes many forms. Energy conversions establish the climate in which these systems operate. The principal forms of energy that are converted at the ecosystem scale include radiant, latent, mechanical, chemical and fossil, and thermal. The book begins with radiant energy absorbed by ecosystems—a phenomenon that is independent of their surface temperature and that can be looked on as a burden or a gift, depending on circumstances. An increase in such absorption raises surface temperature, as described in the fulcrum chapter of the book, Chapter VIII. This increase in turn sets into action outflows of energy that by the first law of thermodynamics are equal in energy units, although not necessarily equal in quality to the inflows. The final chapters deal with vertical stratification and areal contrasts in energy budgets, the augmented energy budget of the city, and the responses that serve to keep the budget balanced.