Climate is the long-term weather pattern in an area, typically averaged over 30 years (defned by theWorld Meteorological Organization (WMO)).[1][2] More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years.[1] Some of the meteorological variables that are commonly measured are temperature, humidity, atmospheric pressure, wind, and precipitation. In a broader sense, climate is the state of the components of the climate system, including the atmosphere, the hydrosphere, the cryosphere, the lithosphere and the biosphere and the interactions between them.[1] The climate of a location is affected by its latitude/longitude, terrain, altitude, and nearby water bodies and their currents. Climates can be classified according to the average and typical variables, most commonly temperature and precipitation. The most widely used classification scheme was the Köppen climate classification. The Thornthwaite system,[3] in use since 1948, incorporates evapotranspiration along with temperature and precipitation information and is used in studying biological diversity and how climate change affects it. Finally, the Bergeron and Spatial Synoptic Classification systems focus on the origin of air masses that define the climate of a region. hide