20.1: Earth's Energy Budget

To understand the global climate of Earth, it is important to understand the energy budget of the Earth, which drives the overall climate of the globe. The biodiversity section discusses how the sun’s energy is unevenly distributed across the Earth’s surface (which leads to the distribution of biomes and the pattern of the seasons); however, here we will consider the totality of energy the Earth receives from the sun across its entire surface (Fig 3.1.1). The majority of energy received from the sun (70%) is absorbed by the Earth’s surface or atmosphere while the rest (30%) is reflected directly back out to space. The Earth’s surface radiates a large amount of energy back up to the atmosphere (this value includes both the energy absorbed from the sun and the energy reabsorbed by the Earth’s surface from the atmosphere), some of which is radiated back out to space, and much of which is retained in the atmosphere and reabsorbed by the Earth’s surface.