text: In contrast, if the entire Earth was covered by water – a so-called ocean planet – the average temperature on the planet would rise to almost .In 2021, scientists reported that Earth dimmed by ~0.5% over two decades (1998–2017) as measured by earthshine using modern photometric techniques.This may have both been co-caused by climate change as well as a substantial increase in global warming.However, the link to climate change has not been explored to date and it is unclear whether or not this represents an ongoing trend.White-sky, black-sky, and blue-sky albedo For land surfaces, it has been shown that the albedo at a particular solar zenith angle θi can be approximated by the proportionate sum of two terms: the directional-hemispherical reflectance at that solar zenith angle, , sometimes referred to as black-sky albedo, and the bi-hemispherical reflectance, , sometimes referred to as white-sky albedo.with being the proportion of direct radiation from a given solar angle, and being the proportion of diffuse illumination, the actual albedo (also called blue-sky albedo) can then be given as: This formula is important because it allows the albedo to be calculated for any given illumination conditions from a knowledge of the intrinsic properties of the surface.Human activities Human activities (e.g., deforestation, farming, and urbanization) change the albedo of various areas around the globe.As per Campra et al., human impacts to "the physical properties of the land surface can perturb the climate by altering the Earth’s radiative energy balance" even on a small scale or when undetected by satellites.The tens of thousands of hectares of greenhouses in Almería, Spain form a large expanse of whitened plastic roofs.A 2008 study found that this anthropogenic change lowered the local surface area temperature of the high-albedo area, although changes were localized.A follow-up study found that "CO2-eq.