1.2 Climate and Human Habitation

A key feature of Earth’s physical landscape is climate.

The earth’s ability to receive and absorb sunlight is a primary factor in the earth’s environment, and it also has a big impact on human populations. There are no large cities or human communities in Antarctica because it is so cold; most of the sunlight filtering down to Antarctica is reflected off the earth at that latitude because of the tilt of the earth’s axis and the resulting angle of incoming solar radiation. Answering the basic questions of where most humans live on Earth and why they live there depends on understanding climate.

Angles of sunlight on the earth
The temperature on Earth is dependent on the solar angle of incidence, or the angle at which the light waves from the sun hit the surface of the earth. Areas of the earth that are perpendicular to the sun’s rays receive more energy than other parts where the sun’s rays hit the earth at an oblique angle. Over one year, the equator receives the most amount of light energy from the sun per area; whereas the poles receive the least. At the middle latitudes, there is a moderate angle of incoming light, creating moderate temperature. Solar angle of incidence is the primary determinant of global temperature patterns.

Since the region between the Tropic of Cancer and the Tropic of Capricorn receives the most direct sunlight throughout the year, it’s favorable to plant and animal life, as long as there is adequate moisture or precipitation. Humans have been living in the tropics for a long time, even when the ice sheets were covering parts of the midlatitudes. The problem with the tropics is that the soils are usually of poor quality and the nutrients have been leached out. Today, when we look at the earth and the distribution of human population, two main factors attract human habitation: moderate climates and access to water.

Major lines of latitude

More than 70 percent of the earth’s surface is covered with water. The only problem is that less than 3 percent of the water is fresh, and most of that fresh water is stored in ice caps at the North or South Pole. This leaves less than 1 percent of the world’s fresh water for human use, usually in lakes, rivers, streams, or groundwater and underground aquifers. Climate plays an important role in where humans live because precipitation is necessary for growing crops, raising livestock, and supplying fresh water to urban communities.

Weather refers to the short-term state of the atmosphere. We might refer to the weather as partly sunny or stormy, for example.

Climate, on the other hand, refers to long-term weather patterns and is affected by a place’s latitude, terrain, altitude, and nearby water bodies. Explained another way, “weather” is what you’re wearing today while “climate” is all the clothes in your closet.

Geographers commonly use the Köppen climate classification system to refer to the major climate zones found in the world.

Köppen climate classification system
Basic Climate Regions Based on the Köppen-Geiger Classification System (Local Conditions May Vary Widely)

The various climate types have been broken down into six basic types—A, B, C, D, E, and H—after the Köppen-Geiger classification system. Type H climates are actually a subset of the type E climate category.

  • Type A: Tropical or equatorial climates
  • Type B: Dry or arid climates
  • Type C: Moderate or temperate climates
  • Type D: Cold or continental climates
  • Type E: Polar or extreme climates
  • Type H: (Unclassified) highland climates – Don’t worry about this climate type. We’ll just cover the other five. 😉

Type A: Tropical or Equatorial Climates

The humid tropical type A climate, usually found in the tropics, has warm temperatures year-round with a high level of precipitation, typically in the form of rain. Type A climates have various subgroups that indicate how variably the rainfall is distributed throughout the year. Some type A climates produce a dry season and a wet season (monsoon), while others receive consistent rainfall throughout the year.

Tropical coast beach
Type A climate

Type B: Dry or Arid Climates

The dry type B climate is exemplified by the earth’s desert regions. Temperatures can be extreme, with little precipitation. Type B climate regions experience low rainfall and high temperatures during the day and cooler temperatures at night or during the winter season. Terrain in type B climates can range from sand deserts to prairie grasslands or steppes. Type B climates have fewer trees than most other climate areas.

Namibia is an example of a type B climate.

There is a direct relationship between highlands and type B climates in various places in the world. This climate condition, known as the rain shadow effect, or more accurately, the precipitation shadow effect, occurs when one side of a mountain range receives abundant rainfall while the region on the other side of the mountain range is a desert or has more arid climate conditions. This phenomenon is evident wherever there is terrain with enough elevation to restrict the movement of precipitation-bearing clouds.

Rain shadow effect
Rain shadow effect

Rain shadows are created when prevailing winds carrying moisture rise quickly in elevation up a mountainside, where the air cools and condenses to precipitate out its moisture in the form of rain or snow. By the time the air mass hits the top of the mountain, its moisture is much reduced. The dried air rushes down the other side of the mountain range, where it increases in temperature. The warm, dry air coming off the mountains continues to pull moisture out of the land, resulting in desert or arid climate conditions.

Rain Shadow Effect

The Hawaiian island of Kauai has an extreme example of the rain shadow effect. The island’s windward side receives more rain than almost any other place on Earth: as much as 460 inches (almost 40 feet) a year. Only a part of the island, however, receives that amount of rain. The height of the mountains causes a rain shadow on the dry leeward side, creating semidesert conditions and type B climates.

Kauai from the air – Hawaii helicopter tour 2019

Death Valley in California is also a result of the rain shadow effect. Little rain falls on Death Valley because any moisture in the prevailing winds falls on the western side of the bordering mountain ranges. The whole state of Nevada is dry because of the rain shadow effect. All the rain coming off the Pacific Ocean falls on the coastal mountains and the Sierra Nevada in California. The mountains are high enough to shadow that region of Nevada, and the basin and ranges further the rain shadow effect on a local basis.

Death Valley – Mesquite Flats Sand Dunes

On the other side of the earth, the Himalayas are an excellent example of mountains that create the rain shadow effect. Most of western China has type B climates because of the rain shadow effect caused by high mountains that stop rain clouds from ever reaching the region. The southern side of the Himalayas receives extensive rainfall because of monsoon rains arriving from the Indian Ocean, but western China is essentially a desert. It is sparsely inhabited compared with the high-density regions in China Proper to the east, where rainfall is plentiful.

Type C: Moderate or Temperate Climates

Often described as moderate in temperature and precipitation, type C climates are the most favorable to human habitation in that they host the largest human population densities on the planet. Type C climates are found mostly in the midlatitudes bordering the tropics. Seasonal changes are pronounced, with distinct winters and summers. Winters are cool to cold and summers are usually warm. Precipitation varies from low to high, depending on location. In the United States, C climates dominate the southeast and the West Coast.

Type C climates are not the most widespread on the planet, but they have attracted the largest human populations. One reason for the attraction has been the abundance of forests, farmland, and fresh water found in these regions.

Appalachia is a good example of a type C climate.

Type D: Cold or Continental Climates

Type D climate regions are often found in the interiors of continents away from the moderating influence of large bodies of water. They are often farther north than type C regions, resulting in colder winters. Seasonal variations exist, with cool to hot summers and cold winters. Precipitation is usually in the form of rain in summer and snow in winter. Regions with type D climates can be found in the Great Lakes region of the United States, much of Canada, and a large portion of Russia.

North Dakota
Colder type D climates are prominent in states such as North Dakota, which has the coldest annual winter temperatures of the continental forty-eight states.

Type E: Polar or Extreme Climates

Type E is an extreme climate type found in the polar regions near or to the north of the Arctic Circle and near or to the south of the Antarctic Circle. Regions with type E climates are cold with permanent ice or permafrost year-round. Vegetation is minimal, and there are no trees. Temperatures may warm slightly during the short summer months but rarely rise above 50 degrees.

Mr. Polar Bear says, “This is what I think of those other climates! Oh, and by the way, I live in climate type E.”

A good YouTube channel that covers the major climates of the world is:
GeoDiode.

Key Takeaways

✎ Climate and access to water influences where people live.
✎ Geographers commonly use the Köppen climate classification system.
✎ The rain shadow effect can create a dry climate.
Polar bears stick out their tongues from time-to-time.

Next: 1.3 Physical Geography Facts

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Image Credits for this page:

Sunlight angles
By Thebiologyprimer – Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=38718050
Latitude circles
By Thesevenseas (talk) – Own work based on World.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8041933
Koppen-Geiger Climate map – original World Regional Geography textbook
Tropical coast beach
By Nat Edwards – http://www.public-domain-image.com/public-domain-images-pictures-free-stock-photos/nature-landscapes-public-domain-images-pictures/beaches-public-domain-images-pictures/tropical-coast-beach.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=24894270
Rain shadow effect
By Wade Greenberg-Brand/Paleontological Research Institution – Paleontological Research Institution, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=61561120
Namibia
By Freddy Weber – fotografiert von Freddy Weber (für Benutzer:Roger_Zenner) im August 2004, Public Domain, https://commons.wikimedia.org/w/index.php?curid=18068772
Death Valley
By Tuxyso / Wikimedia Commons, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=28603629
Appalachia barn and Hacker Grist Mill
By Willmeyer1020 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=66465041
North Dakota sign
By formulanone from Huntsville, United States – ND210 West – Welcome to North Dakota Sign, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=74639725
Polar bear
By Christopher Michel – https://www.flickr.com/photos/cmichel67/19443086819/in/dateposted/, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=41530813

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