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).
List of cloud types
The supplementary features are associated with particular genera as follows. They are sorted from left to right in approximate decreasing order of frequency of occurrence for each of three categories. The genus types (including some cumulus sub-types) are arranged from top to bottom in approximate descending order of average overall altitude range.
The possible combinations of genera and mother clouds can be seen in this table. The genitus and mutatus clouds are each sorted from left to right in alphabetical order. The genus types (including some cumulus sub-types) are arranged from top to bottom in the left column in approximate descending order of average overall altitude range.