Question
Suppose the Earth is really flat. Shaped like a penny, it has one side that faces the Sun at all times. Suppose this Earth is the same temperature everywhere (including the side that faces away from the Sun). Neglect any radiation losses off the rim of the Earth and assume there is no albedo or greenhouse effect. Treating it as a perfect blackbody, estimate the temperature of this new, flat Earth. 5. In the article "The Climatic Effects of Nuclear War" (Scientific American, August 1984), the authors calculate a global energy balance corresponding to the first few months following a 5,000-megaton nuclear exchange. The resulting smoke and dust in the atmosphere absorb 75 percent of the incoming sunlight (257 W/m2), while the albedo is reduced to 20 percent. Convective and evaporative heating of the atmosphere from the Earth's surface is negligible as is the energy reflected from the Earth's surface. The Earth's surface radiates 240 W/m2, all of which is absorbed by the atmosphere. Assuming that the Earth can be modeled as a blackbody emitter as shown below, find the following (equilibrium) quantities: 6. a. The temperature of the surface of the Earth (this is "nuclear winter') b. X, the rate at which radiation is emitted from the atmosphere to space c. Y, the rate of absorption of short-wavelength solar radiation at the Earth's surface d. Z, the rate at which the atmosphere radiates energy to the Earth's surface Incoming 342 W/m2 Radiated to space Reflected Reflected 69 Atmosphere Convection, evaporation Absorbed 257 Radiated 240 W/in Absorbed Radiated to ground
Explanation / Answer
5. Since the Earth acts as a perfect blackbody,its temperature is likely to be 2.75K
