Eocene
Another method considered for producing the warm polar temperatures were polar stratospheric clouds. Polar stratospheric clouds are clouds that occur in the lower stratosphere at very low temperatures. Polar stratospheric clouds have a great impact on radiative forcing. Due to their minimal albedo properties and their optical thickness, polar stratospheric clouds act similar to a greenhouse gas and traps outgoing longwave radiation. Different types of polar stratospheric clouds occur in the atmosphere: polar stratospheric clouds that are created due to interactions with nitric or sulfuric acid and water (Type I) or polar stratospheric clouds that are created with only water ice (Type II).
Cloud (video game)
The game contains three types of clouds: white clouds, which follow the avatar; gray, neutral clouds, which become white when touched; and black clouds, which may be combined with white clouds to cause rain, dissolving both clouds. A large number of white clouds more easily dissolves a small number of dark clouds than an equal number, and vice versa. White clouds stop following the avatar if the player moves too quickly and they resume following if approached again. Each of the four missions in "Cloud" has a different objective, including forming patterns in the sky with clouds, eliminating black clouds, and creating rain over each of the islands.