The major classification systems of world climate are:
Köppen climate classification system
This is one of the most widely used climate classification systems. It classifies climates based on annual and monthly average temperature and precipitation. It uses vegetation as an indicator of climate. There are 5 main climate groups in this system:
A: Tropical climates
B: Dry climates
C: Moderate climates with mild winters and dry summers
D: Cold climates with dry winters
E: Polar climates
Thornthwaite climate classification system
This system mainly uses plant cover and evapotranspiration rates to classify climates. It divides climates into 5 major groups based on moisture index:
Hyperthermic: High evapotranspiration, very dry climates
Mesothermic: Moderate evapotranspiration, dry-subhumid climates
Microthermic: Low evapotranspiration, humid climates
Cryic: Low evapotranspiration, cold climates with short growing seasons
Aquic: Permanent excess of moisture
Trewartha climate classification
This system classifies climates based on temperature and precipitation conditions. It uses temperature seasonality and moisture status as the primary variables. There are 6 major climate groups:
A: Tropical climates
B: Dry climates
C: Temperate climates with hot summers
D: Continental climates with cold winters
E: Polar climates
F: Climates with significant water surplus throughout the year
So in summary, the major classification systems are the Köppen system based on temperature and precipitation, the Thornthwaite system based on moisture indices, and the Trewartha system based on temperature seasonality and moisture status. Each system categorizes climates into different groups based on its particular focus and variables.