'Vegetation is the true index of climate'. This statement is associated with

The correct answer is B) Koppen. Wladimir Köppen, a climatologist and botanist, built his climate classification on the idea that natural vegetation is the most visible and reliable expression of climate. His system uses monthly temperature and precipitation thresholds, and its major groups (A to E) were chosen so that they match broad vegetation zones such as tropical rainforest, desert, grassland and tundra.

• Thornthwaite (A) is wrong. His schemes of 1931 and 1948 use potential evapotranspiration and a water balance (moisture index), not vegetation as the index.
• Trewartha (C) is wrong. He modified Köppen's scheme to suit mid-latitude and subtropical regions, but he did not present vegetation as the true index of climate.
• Stamp (D) is wrong. L. Dudley Stamp is known for land use and land classification work, including the Land Utilisation Survey of Britain, not for a vegetation-based climate classification.

Core concept: genetic versus empirical climate classification. Köppen's scheme is a genetic classification, which is central to Geography Optional and useful for Mains answers on climate, vegetation and soil linkages in India.

Trap: candidates pick Thornthwaite because his name is strongly linked with climate classification and the word index suggests a quantitative water-based measure. Remember that Thornthwaite's index is water-based, while Köppen's is vegetation-linked.