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).
Cumulus cloud
The species "Cumulus fractus" is ragged in appearance and can form in clear air as a precursor to cumulus humilis and larger cumulus species-types; or it can form in precipitation as the supplementary feature "pannus" (also called scud) which can also include stratus fractus of bad weather. "Cumulus humilis" clouds look like puffy, flattened shapes. "Cumulus mediocris" clouds look similar, except that they have some vertical development. "Cumulus congestus" clouds have a cauliflower-like structure and tower high into the atmosphere, hence their alternate name "towering cumulus". The variety "Cumulus radiatus" forms in radial bands called cloud streets and can comprise any of the four species of cumulus.
Cumulus supplementary features are most commonly seen with the species congestus. "Cumulus virga" clouds are cumulus clouds producing virga (precipitation that evaporates while aloft), and "cumulus praecipitatio" produce precipitation that reaches the Earth's surface. "Cumulus pannus" comprise shredded clouds that normally appear beneath the parent cumulus cloud during precipitation. "Cumulus arcus" clouds have a gust front, and "cumulus tuba" clouds have funnel clouds or tornadoes. "Cumulus pileus" clouds refer to cumulus clouds that have grown so rapidly as to force the formation of pileus over the top of the cloud. "Cumulus velum" clouds have an ice crystal veil over the growing top of the cloud.