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Due to differences in emissivity, this infrared picture of a cold beer can shows vastly different (and incorrect) temperature values depending on the surface material. Reflections (like on the blank end of the can and the countertop) make accurate measurements of reflective surfaces impossible.
Mid-to-high-latitude forests have a much lower albedo during snow seasons than flat ground, thus contributing to warming. Modeling that compares the effects of albedo differences between forests and grasslands suggests that expanding the land area of forests in temperate zones offers only a temporary mitigation benefit. [51] [52] [53] [54]
Emissivity can in general depend on wavelength, direction, and polarization. However, the emissivity which appears in the non-directional form of the Stefan–Boltzmann law is the hemispherical total emissivity, which reflects emissions as totaled over all wavelengths, directions, and polarizations. [3]: 60
Thermal emittance or thermal emissivity is the ratio of the radiant emittance of heat of a specific object or surface to that of a standard black body.Emissivity and emittivity are both dimensionless quantities given in the range of 0 to 1, representing the comparative/relative emittance with respect to a blackbody operating in similar conditions, but emissivity refers to a material property ...
The emissivity of Earth's surface has been measured to be in the range 0.65 to 0.99 (based on observations in the 8-13 micron wavelength range) with the lowest values being for barren desert regions. The emissivity is mostly above 0.9, and the global average surface emissivity is estimated to be around 0.95. [13] [14]
The effective temperature of the Sun (5778 kelvins) is the temperature a black body of the same size must have to yield the same total emissive power.. The effective temperature of a star is the temperature of a black body with the same luminosity per surface area (F Bol) as the star and is defined according to the Stefan–Boltzmann law F Bol = σT eff 4.
The albedo and emissivity of the Moon are about 0.1054 [45] and 0.95 [46] respectively, yielding an estimated temperature of about 1.36 °C. Estimates of the Earth's average albedo vary in the range 0.3–0.4, resulting in different estimated effective temperatures.
Spectral hemispherical emissivity: ε ν ε λ — Spectral exitance of a surface, divided by that of a black body at the same temperature as that surface. Directional emissivity: ε Ω — Radiance emitted by a surface, divided by that emitted by a black body at the same temperature as that surface. Spectral directional emissivity: ε Ω,ν ε ...