In general, any effort to alter artificially the natural phenomena of the atmosphere. The term usually refers to cloud seeding activities, but can also include constructing windbreaks, dissipating fog by the forceful addition of heat or water spray, or preventing frost formation on crops by cloud spray, heating, or mixing processes. Inadvertent weather modification refers to accidental weather effects resulting from the release of greenhouse gases, aerosols, and dust, or changes in albedo or surface properties of the earth associated with urban, industrial, or agricultural activity.