Figure 18.2
World map of deserts. The Köppen climate system (see Section 8.1) classifies arid and semiarid regions as BWh and BWk climates. Arid climates are found on all continents. Deserts of about 500,000 km2 (193,000 mi2) or greater, excluding those of Antarctica and the Arctic, are labeled on this map. The main causes of their aridity are given in the table.