Climatic regions of the world

Story hook

It is 1884. Wladimir Köppen, a Russian-German climatologist working at the Hamburg observatory, has spent a decade staring at temperature and rainfall data from hundreds of weather stations worldwide. He notices something elegantly obvious that no one has formalised: vegetation maps and climate maps are the same map. Where rainforest grows, the climate must support it. Where deserts are found, conditions exclude trees. Where tundra hugs the pole, only mosses and lichens can persist.

He publishes the first climate classification grounded in vegetation — a system of letters where A means tropical, B means dry, C means warm temperate, D means cold continental, and E means polar. Lower-case letters refine each: Af is rainforest, Aw is savanna, Bsh is hot semi-arid (Hyderabad, parts of Africa), Cs is Mediterranean, Et is tundra, Ef is ice cap. Tweaks come in 1918 and 1936 (with Rudolf Geiger), giving us the Köppen-Geiger system that still appears on every IPCC map a century later.

For UPSC, you must internalise this map — because every climatic region question on Prelims maps to one of these letter codes, and every Mains discussion of agriculture, vegetation, or human adaptation begins with the climate category.

Why this matters for UPSC

Syllabus location: GS-I — World Physical Geography (Climatic regions, Köppen system). Asked 3-4 times in Prelims over 10 years; major Mains coverage (climate change impacts on specific climate zones). Climate type drives agriculture + vegetation + population distribution + economic geography — it's the master variable for the rest of the GS-I syllabus.