Earth ’ S Global Energy Budget

W eather and climate on Earth are determined by the amount and distribution of incoming radiation from the sun. For an equilibrium climate, OLR1 necessarily balances the incoming ASR, although there is a great deal of fascinating atmosphere, ocean, and land phenomena that couple the two. Incoming radiant energy may be scattered and reflected by clouds and aerosols or absorbed in the atmosphere. The transmitted radiation is then either absorbed or reflected at the Earth’s surface. Radiant solar or shortwave energy is transformed into sensible heat, latent energy (involving different water states), potential energy, and kinetic energy before being emitted as longwave radiant energy. Energy may be stored for some time, transported in various forms, and converted among the different types, giving rise to a rich variety of weather or turbulent phenomena in the atmosphere and ocean. Moreover, the energy balance can be upset in various ways, changing the climate and associated weather. Kiehl and Trenberth (1997, hereafter KT97) reviewed past estimates of the global mean flow of energy through the climate system and presented a new global mean energy budget based on various measurements and models. They also performed a number of radiative computations to examine the spectral features of the incoming and outgoing radiation and determined the role of clouds and various greenhouse gases in the overall radiative energy flows. At the TOA, values relied heavily on observations from the ERBE from 1985 to 1989, when the TOA values were approximately in balance. In this paper we update those estimates based on more recent observations, which include improvements in retrieval methodology and hardware, and discuss continuing sources of uncertainty. State-of-the-art radiative models for both longwave and shortwave spectral regions were used by KT97 to partition radiant energy for both clear and cloudy skies. Surface sensible and latent heat estimates were based on other observations and analyses. During ERBE, it is now thought that the imbalance EARTH’S GLOBAL ENERGY BUDGET