World Climate and Climate Change — Class 11 Geography

Climates can be classified by empirical, genetic and applied approaches. The most widely used is V. Koeppen's empirical scheme, based on mean monthly and annual temperature and precipitation and on a close relationship between climate and vegetation. Koeppen used capital letters for five major groups: A (tropical humid), B (dry climates), C (warm temperate or mid-latitude), D (cold snow-forest) and E (cold/polar), with small letters (f, m, w, s) for seasonal dryness. The chapter describes the sub-types — tropical wet (Af), tropical monsoon (Am), tropical wet and dry (Aw), subtropical steppe and desert (BSh, BWh), Mediterranean (Cs), humid subtropical and marine west coast climates, and tundra (ET) and ice-cap (EF) polar climates. Climate change is a natural and continuous process: the earth has seen glacial and inter-glacial periods, and India experienced wet and dry phases (the Rajasthan desert was wetter around 8000 BCE; Europe had a "Little Ice Age" from 1550 to 1850). Causes of climate change are astronomical (sunspots, Milankovitch oscillations) and terrestrial (volcanism, greenhouse gases). The most important human effect is the increasing concentration of greenhouse gases (carbon dioxide, CFCs, methane, nitrous oxide, ozone), which causes global warming and ozone depletion; the Kyoto Protocol (1997) sought to reduce emissions.