On a global scale, the Koppen-Geiger Climate Classification is a system most widely used for ecological modeling such as climate change impact assessments. It divides the world into five main climate groups: equatorial (A), arid (B), warm-temperate (C), snow (D), and polar (E). The five main climate groups are further subdivided based on precipitation and temperature. Precipitation categories include desert (W), steppe (S), fully humid (f), dry summer (s), dry winter (w), and monsoon (m). Temperature categories include hot arid (h), cold arid (k), hot summer (a), warm summer (b), cool summer (c), extremely continental (d), polar frost (F), or polar tundra (T).