What does albedo measure?

Albedo is a measure of the reflectivity of a surface, specifically the proportion of shortwave radiation (such as sunlight) that is reflected back into space. A surface with a high albedo reflects a greater amount of incoming solar radiation, while a surface with a low albedo absorbs more radiation. This characteristic is crucial in understanding the Earth's energy balance and climate dynamics.

For instance, snow and ice have high albedo values, which means they reflect most of the solar energy they receive, helping to keep temperatures lower. Conversely, darker surfaces such as forests or oceans absorb more incoming radiation, contributing to heat retention. This concept is essential in fields like climatology and environmental science, as it influences local and global temperature patterns.

The other options, while related to energy and radiation in the atmosphere, do not accurately define albedo. Albedo specifically focuses on reflectivity, rather than heat absorption, total solar energy received, or humidity levels.