Climate zones

Definition

Climate—the average weather conditions over a period of at least thirty years—is determined by various factors, the most important of which are precipitation amounts and air temperature. Climate controls the major ecological community types, or biomes; that is, the climate in a given region determines the flora and fauna that will thrive in that region. In 1900, Wladimir Köppen, a German climatologist, developed what became the most widely used system for classifying world climates. The Köppen system identifies five major climate zones: tropical moist climates (A zone), dry climates (B zone), humid middle latitude climates (C zone), continental climates (D zone), and cold climates (E zone).

Köppen also used two subgroups to more specifically describe the zones. The first subgroup uses lowercase letters to show how precipitation is distributed throughout the year—for example, f for no dry season, s for a dry summer, or w for a dry winter. The second subgroup uses lowercase letters to indicate temperature patterns—such as a for hot summers, b for warm summers, or c for cool summers. When combined, these letters create a three-part code. For instance, Cfa represents a humid middle-latitude climate (C) with no dry season (f) and hot summers (a). This system allows scientists and geographers to classify climates around the world in a clear and consistent way.

Tropical moist climates are characterized by year-round high temperatures and large amounts of rain. Rainfall is adequate all year round, and there is no dry season. This zone is typical of northern parts of South America, Central Africa, Malaysia, Indonesia, and Papua New Guinea. The dry climate zone has little rain and a wide range of daily temperatures. There is a dry season in the summer and winter, with a mean annual temperature of 18 degrees Celsius (64.4 degrees Fahrenheit), as in the western United States, northern and extreme Southern Africa, parts of Central Asia, and most of Australia.

The humid middle latitude climate, or temperate zone, has hot-to-warm, dry summers and cool, wet winters, but no dry season as such. Southeastern sections of the United States and South America, westernmost Europe, and the southeast corner of China fit this category. The continental climate zone, in interior regions of large land masses such as Canada, Northern Europe, and Asia, experiences varied seasonal temperatures and moderate rainfall. The cold climate zone, characterized by permanent ice and ever-present tundra, occupies Greenland and the most northerly parts of Asia.

Significance for Climate Change

While acknowledging some unknowns and uncertainty, researchers predict that, if global warming caused by carbon dioxide (CO₂) and other greenhouse gas (GHG) emissions continues at the rate observed in the beginning of the twenty-first century, some climate zones could disappear entirely by the end of the century, giving way to new climate zones on up to 39 percent of the world’s land surface. Major areas that could be affected are tropical highlands and polar regions. Broad strips of areas labeled tropics and subtropics at the beginning of the twenty-first century could develop new climates that do not resemble any of the zones in categories assigned in the Köppen Climate Classification System. Heavily populated areas such as the southeastern United States, southeastern Asia, parts of Africa, such as its mountain ranges, the Amazonian Rainforest, and South American mountain ranges are likely to be the most severely affected.

Climate change patterns could affect ecosystems on a global scale. For example, major changes in North American forests could result. Four tree species—the yellow birch, the sugar maple, the hemlock, and the beech—are expected to move northward up to 1,000 kilometers (around 621 miles) while abandoning their present-day locations entirely. Animals could also be affected, as temperature and rainfall patterns could change breeding and migration patterns.

For humans, a grave concern was global food production. One model predicted that the corn belt in North America would move northward, possibly as far as Canada, and a 2022 study suggested that by 2100, the corn belt, or the corn production area of the midwestern United States, would be unable to produce corn without large advancements in agricultural technology. Winter wheat may replace corn in parts of the corn belt. Other scientists predicted various changes over the course of the twenty-first century. The Swiss Alps could become a Mediterranean climate, with wet winters and long, dry, warm summers. The climate zone in southern Switzerland may move northward by as much as 500 kilometers (310.6 miles). In the western Alps, the climate may come to resemble the climate in southern France.

Scientists also predicted biodiversity in South Africa could be substantially affected by shifting climate zones: Species extinction on a wide scale; new climate zones in up to half the country; suffering succulent karoo, a globally important arid-climate hotspot, and suffering biomes in the fynbos (a Mediterranean-climate thicket) will suffer. While the degree of this change remains speculative, the availability of food could affect sub-Saharan West Africa, as vegetation zones move southward.

With continued deforestation in the Amazonian forest areas of South America, new climates will be created near the equator. Some researchers predict that mountainous areas such as those found in Peru and the Colombian Andes, as well as regions in Siberia and southern Australia, could experience the complete disappearance of climates. Devastation to critical ecosystems and changes in agricultural patterns could severely affect Australia, New Zealand, and the developing island nations of the Pacific. Rising global temperatures are expected to intensify droughts, wildfires, and extreme weather events, which in turn puts pressure on water supplies and reduces crop yields. Shifts in rainfall patterns could disrupt traditional farming cycles, while warming oceans may lead to more powerful tropical storms and widespread coral reef damage. Low-lying island nations are especially vulnerable to sea-level rise and coastal erosion, which threaten homes, infrastructure, and freshwater resources. These challenges could jeopardize food security, displace communities, and place increasing strain on regional economies and natural ecosystems. With so many unknown factors, it remains to be seen how climate zone changes will play out in the future.

Bibliography

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Clark, Carol. “Climate Change on Course to Hit US Corn Belt Especially Hard, Study Finds.” Emory University News Center, 2 June 2022, news.emory.edu/stories/2022/06/esc_climate_change_corn_belt_02-06-2022/story.html. Accessed 30 Jan. 2023.

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Diaz, Henry F., and Richard J. Murnane, editors. Climate Extremes and Society. Cambridge UP, 2008.

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"Köppen Climate Classification System." National Geographic Society, 19 July 2024, education.nationalgeographic.org/resource/koppen-climate-classification-system/. Accessed 18 Sept. 2025.

"State of the Climate 2024: Australia Is Enduring Harsher Fire Seasons, More Ocean Heatwaves and Sea-Level Rise." CSIRO, 1 Nov. 2024, www.csiro.au/en/news/all/articles/2024/november/state-of-the-climate-2024. Accessed 18 Sept. 2025.