Albedo reflectance and bi-hemispherical reflectance (e.g.,). These calculations are based on the bidirectional reflectance distribution function (BRDF), which describes how the reflectance of a given surface depends on the view angle of the observer and the solar angle. BDRF can facilitate translations of observations of reflectance into albedo. Earth's average surface temperature due to its albedo and the greenhouse effect is currently about 15 °C. If Earth were frozen entirely (and hence be more reflective), the average temperature of the planet would drop below −40 °C. If only the continental land masses became covered by glaciers, the mean temperature of the
Cloud albedo if all other factors are the same. Addition of cloud nuclei by pollution can lead to an increase in solar radiation reflected by clouds. Increasing aerosol concentration and aerosol density increases cloud droplet concentration, decreases cloud droplet size, and increases cloud albedo. In macrophysically identical clouds, a cloud with few larger drops will have a lower albedo than a cloud with more smaller drops. The cloud albedo increases with the total water content or depth of the cloud and with the solar zenith angle. The variation of albedo with zenith angle is most rapid when the sun is near the