How Earth's Climate Zones and Biomes Are Classified

What decides a region's climate

NOAA defines climate as the recurring average weather observed in a given place over roughly 30-year intervals. The agency attributes broader worldwide climate patterns to Earth's axial tilt, rotation and the uneven distribution of land and sea, according to NOAA's JetStream climate education site.

The Köppen-Geiger system: five letters cover the planet

The most widely used framework for sorting these patterns is the Köppen climate classification, created by Russian-German geographer and climatologist Wladimir Köppen, who linked climate boundaries to observed vegetation zones. Köppen published his first classification map in the early 1900s and kept refining it until his death in 1940, according to National Geographic Education. Climatologist Rudolf Geiger later added further subdivisions, and the system has continued to be updated since, most recently in 2018.

NOAA also lists a sixth category, Zone H for highlands, where elevation can create sharply different microclimates within short distances in mountainous terrain.

Within these broad letters, Köppen-Geiger maps add further codes for rainfall pattern and temperature extremes — for instance, hot deserts (BWh) versus cold deserts (BWk), or tropical climates with no dry season (Af) versus those with a winter dry season (Aw), National Geographic Education notes.

Climate zones versus biomes: what's the difference

A climate zone and a biome are related but not identical. NOAA describes climate as the recurring average weather of a region, while NASA's Earth science education materials define a biome as a community of plants and animals that live together in a particular kind of climate. Because vegetation and wildlife track regional climate, the two terms are sometimes used loosely as synonyms, though they describe different things — one is a climate classification, the other the living community that develops within it.

The major biomes found within these zones

NASA's Earth science education materials group land biomes into seven broad types: rainforest, grassland, coniferous forest, temperate deciduous forest, desert, tundra and shrubland. National Geographic Education groups them slightly differently into five major biome categories — aquatic, grassland, forest, desert and tundra — each defined by its own climate signature.

• Forest: covers roughly one-third of Earth's land and ranges from warm, humid tropical rainforest to temperate forests with four seasons to cold, dry boreal taiga, per National Geographic Education.
• Grassland: warm and comparatively dry, with tropical savannas near the equator supporting scattered trees and temperate grasslands farther away typically treeless; savannas cover almost half of Africa and grasslands are also found in Australia, India, South America, Hungary, Argentina and Russia, per National Geographic Education.
• Desert: receives less than 50 centimeters (20 inches) of rain a year and covers about 20% of Earth's surface, per National Geographic Education.
• Tundra: average yearly temperatures range from about -34°C to 12°C with only 15-25 centimeters of annual precipitation, according to National Geographic Education.
• Aquatic: freshwater biomes such as ponds, rivers and lakes, while marine biomes, including oceans and coral reefs, cover nearly three-quarters of Earth's surface, according to National Geographic Education.

Because each biome's vegetation and wildlife track the temperature and rainfall of its climate zone, shifts in regional climate can gradually change which biome a landscape supports — one reason researchers continue to use Köppen-Geiger maps, originally built from 19th- and 20th-century vegetation surveys, to track how climate patterns are distributed today.