Introduction

World climate is far too vast and varied to describe one place at a time. To make it manageable, geographers study climate by organising the enormous amount of information and data available and synthesising it into smaller, more workable units. Grouping similar climates together makes them easier to understand, describe, and analyse — rather than treating every single location on earth as a unique, unrelated case.

Three broad approaches have been developed for classifying climate this way:

• Empirical classification — based directly on observed data, particularly temperature and precipitation. This approach starts from what is actually measured on the ground rather than from theory.
• Genetic classification — attempts to organise climates according to their causes, such as the atmospheric and oceanic processes that produce a given set of climatic conditions, rather than only their observed effects.
• Applied classification — designed for a specific purpose, tailored to whatever practical question the classification is meant to answer, rather than being a general-purpose scheme.

These three approaches are not competing so much as complementary — each answers a different kind of question about climate. The chapter goes on to use one particular scheme built on the empirical approach — developed by the climatologist Wladimir Koeppen — as the framework for classifying and studying the world's climates in detail.