The classification of climate from paleosols can be related using climatically sensitive features of soils that are sensitive to particular climatic variables, but even the best of these features lack precision. This is because soils are not as sensitive as meteorological instruments for recording climatic conditions. However, in a fairly broad category, climate can be interpreted from the sensitive features found in soils. One of the most large-scale influences regarding the classification of climate was created in 1918, then modified over two decades by the German meteorologist Vladimir Köppen (Trewartha 1982). He proposed there are five main climate groups (Köppen climate classification), each corresponding to the main types of terrestrial vegetation. Each climate type is designated by letters, with upper-case letters referring to the main climate groups and lower-case letters referring to subsidiary climatic features. (Retallack 2001)