At the start of each lunation a very unique event involving the reflectivity of sunlight from earth can be observed to unfold over a two to three day span and which forms the basis for climatic studies on earth. The reflection of light, particularly from cloud- or ice-covered portions of the earth, can allow for the visibility of the dark side of the moon when this light is re-reflected back to an observer on earth! This phenomenon is most commonly described as "Earthshine" but is also known by such esoteric terms as "Ashen Glow" and "the old Moon in the New Moon's arms" in various circles and was first explained by da Vinci five centuries ago.

This phenomenon is an indirect measure of the earth's albedo (0.297 + 0.005) and varies as a function of season with springs characterized with a greater albedo and brighter earthshine moons as opposed to similar events during the summer and fall. An associated benefit of greater reflected sunlight is that the planet is thereby cooler.

Studies have revealed that cloud cover reflects approximately one-half or 50% of the sunlight that is directed at them and this figure is only superceeded by snow and ice which are able to reflect anywhere from 40 to 90% of similar sunlight that hits them. In contrast, oceans reflect a miniscule 10% of sunlight and land masses only slightly more at 10-25%. Due to the planet's rotation, the amount of reflected light will be dynamic as different portions of the globe will be reflecting sunlight towards the dark side of the moon; for example, an observer in California will observe a brighter Earthshine Crescent Moon due to the sun rising over a large land mass such as Asia as compared to the Pacific Ocean body of water and its relatively lesser reflectivity!