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).
Mushroom cloud
For ground and low-altitude bursts, the cloud contains also vaporized, melted and fused soil particles. The distribution of activity through the particles depends on their formation. Particles formed by vaporization-condensation have activity evenly distributed through volume as the air-burst particles. Larger molten particles have the fission products diffused through the outer layers, and fused and non-melted particles that were not heated sufficiently but came in contact with the vaporized material or scavenged droplets before their solidification have a relatively thin layer of high activity material deposited on their surface. The composition of such particles depends on the character of the soil, usually a glass-like material formed from silicate minerals. The particle sizes do not depend on the yield but instead on the soil character, as they are based on individual grains of the soil or their clusters. Two types of particles are present, spherical, formed by complete vaporization-condensation or at least melting of the soil, with activity distributed evenly through the volume (or with a 10–30% volume of inactive core for larger particles between 0.5–2 mm), and irregular-shaped particles formed at the edges of the fireball by fusion of soil particles, with activity deposited in a thin surface layer. The amount of large irregular particles is insignificant. Particles formed from detonations above, or in, the ocean, will contain short-lived radioactive sodium isotopes, and salts from the sea water. Molten silica is a very good solvent for metal oxides and scavenges small particles easily; explosions above silica-containing soils will produce particles with isotopes mixed through their volume. In contrast, coral debris, based on calcium carbonate, tends to adsorb radioactive particles on its surface.