Publications associated with Climate Dynamics

Infrared radiation and planetary temperature

Physics Today 64 (2011) 33-38

RT Pierrehumbert

In a single second, Earth absorbs 1.22×10 17 joules of energy from the Sun. Distributed uniformly over the mass of the planet, the absorbed energy would raise Earth's temperature to nearly 800000 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 5-50μm 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, about a quarter century after IR radiation was discovered by William Herschel. As Fourier also recognized, the rate at which electromagnetic radiation escapes to space is strongly affected by the intervening atmosphere. With those insights, Fourier set in motion a program in planetary climate that would take more than a century to bring to fruition. © 2011 American Institute of Physics.

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