In a single second, Earth absorbs 1.22 × 1017 joules of energy from the Sun. Distributed uniformly over the mass of the planet, the absorbed energy would raise Earth’s temperature to nearly 800 000 K after a billion years, if Earth had no way of getting rid of it. For a planet sitting in the near-vacuum of outer space, the only way to lose energy at a significant rate is through emission of electromagnetic radiation, which occurs primarily in the subrange of the IR spectrum with wavelengths of 5–50 µm for planets with temperatures between about 50 K and 1000 K. For purposes of this article, that subrange is called the thermal IR. The key role of the energy balance between short-wave solar absorption and long-wave IR emission was first recognized in 1827 by Joseph Fourier,1 , 2 about a quarter century after IR radiation was discovered by...
Infrared radiation and planetary temperature
Raymond T. Pierrehumbert; Infrared radiation and planetary temperature. Physics Today 1 January 2011; 64 (1): 33–38. https://doi.org/10.1063/1.3541943
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