Consider the Earth’s energy balance shown in Figure 18.12.

Figure 18.12

(a) How many different sources transfer energy to the atmosphere? Which makes the largest contribution? What is the total amount of energy transferred into the atmosphere in W/m²? 

(b) To maintain a balance the atmosphere must lose an equal amount of energy by emitting radiation, either into space or back toward the surface. What fraction is radiated back to the surface?

Transcribed Image Text:

Go Figure What is the total amount of energy absorbed by the surface? What fraction of that energy is emitted upward as infrared radiation? Reflected Solar Radiation 107 W/m² Reflected by clouds Aerosol and Atmosphere 77 W/m² Reflected by Surface 30 W/m² 168 W/m² Absorbed by Surface Incoming Solar Radiation 342 W/m² Absorbed by Atmosphere 67 W/m² 24 W/m² Convective Heating Emitted by Atmosphere 195 W/m² 390 W/m² Surface Radiation ▲ Figure 18.12 Earth's thermal balance. The amount of radiation reaching the surface of the planet is equal to the amount radiated back into space. Outgoing Longwave Radiation 235 W/m² Radiation not Absorbed by Atmosphere 40 W/m² Back Radiation 324 W/m² Greenhouse Gases 78 W/m² Evapo- transpiration