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    Climate is the long-term pattern of weather in a particular area. Weather can change from hour-to-hour, day-to-day, month-to-month or even year-to-year. A region’s weather patterns, usually tracked for at least 30 years, are considered its climate.
     
    Climate System
     
    Different parts of the world have different climates. Some parts of the world are hot and rainy nearly every day. They have a tropical wet climate. Others are cold and snow-covered most of the year. They have a polar climate. Between the icy poles and the steamy tropics are many other climates that contribute to Earth’s biodiversity and geologic heritage.
     
    Climate is determined by a region’s climate system. A climate system has five major components: the atmosphere, the hydrosphere, the cryosphere, the land surface, and the biosphere. 
     
    The atmosphere is the most variable part of the climate system. The composition and movement of gases surrounding the Earth can change radically, influenced by natural and man-made factors.
     
    Changes to the hydrosphere, which include variations in temperature and salinity, occur at much slower rates than changes to the atmosphere. 
     
    The cryosphere is another generally consistent part of the climate system. Ice sheets and glaciers reflect sunlight, and the thermal conductivity of ice and permafrost profoundly influences temperature. The cryosphere also helps regulate thermohaline circulation. This “ocean conveyor belt” has an enormous influence on marine ecosystems and biodiversity.
     
    Topography and vegetation influence climate by helping determine how the Sun’s energy is used on Earth. The abundance of plants and the type of land cover (such as soil, sand, or asphalt) impacts evaporation and ambient temperature.
     
    The biosphere, the sum total of living things on Earth, profoundly influences climate. Through photosynthesis, plants help regulate the flow of greenhouse gases in the atmosphere. Forests and oceans serve as “carbon sinks” that have a cooling impact on climate. Living organisms alter the landscape, through both natural growth and created structures such as burrows, dams, and mounds. These altered landscapes can influence weather patterns such as wind, erosion, and even temperature. 
     
    Climate Features
    The most familiar features of a region’s climate are probably average temperature and precipitation. Changes in day-to-day, day-to-night, and seasonal variations also help determine specific climates. For example, San Francisco, California, and Beijing, China, have similar yearly temperatures and precipitation. However, the daily and seasonal changes make San Francisco and Beijing very different. San Francisco’s winters are not much cooler than its summers, while Beijing is hot in summer and cold in winter. San Francisco’s summers are dry and its winters are wet. Wet and dry seasons are reversed in Beijing—it has rainy summers and dry winters. 
     
    Climate features also include windiness, humidity, cloud cover, atmospheric pressure, and fogginess. Latitude plays a huge factor in determining climate. Landscape can also help define regional climate. A region’s elevation, proximity to the ocean or freshwater, and land-use patterns can all impact climate.
     
    All climates are the product of many factors, including latitude, elevation, topography, distance from the ocean, and location on a continent. The rainy, tropical climate of West Africa, for example, is influenced by the region’s location near the Equator (latitude) and its position on the western side of the continent. The area receives direct sunlight year-round, and sits at an area called the intertropical convergence zone (ITCZ, pronounced “itch”), where moist trade winds meet. As a result, the region’s climate is warm and rainy.
     
    Microclimates
    Of course, no climate is uniform. Small variations, called microclimates, exist in every climate region. Microclimates are largely influenced by topographic features such as lakes, vegetation, and cities. In large urban areas, for example, streets and buildings absorb heat from the Sun, raising the average temperature of the city higher than average temperatures of more open areas nearby. This is known as the “urban heat island effect.” 
     
    Large bodies of water, such as the Great Lakes in the United States and Canada, can also have microclimates. Cities on the southern side of Lake Ontario, for example, are cloudier and receive much more snow than cities on the northern shore. This “lake effect” is a result of cold winds blowing across warmer lake water.
     
    Climate Classification
     
    In 1948, American climatologist Charles Thornthwaite developed a climate classification system that scientists still use today. Thornthwaite’s system relies on a region’s water budget and potential evapotranspiration. Potential evapotranspiration describes the amount of water evaporated from a vegetated piece of land. Indices such as humidity and precipitation help determine a region’s moisture index. The lower its moisture index value, the more arid a region’s climate.
     
    The major classifications in Thornthwaite’s climate classification are microthermal, mesothermal, and megathermal.
     
    Microthermal climates are characterized by cold winters and low potential evapotranspiration. Most geographers apply the term exclusively to the northern latitudes of North America, Europe, and Asia. A microthermal climate may include the temperate climate of Boston, Massachusetts; the coniferous forests of southern Scandinavia; and the boreal ecosystem of northern Siberia.
     
    Mesothermal regions have moderate climates. They are not cold enough to sustain a layer of winter snow, but are also not remain warm enough to support flowering plants (and, thus, evapotranspiration) all year. Mesothermal climates include the Mediterranean Basin, most of coastal Australia, and the Pampas region of South America.
     
    Megathermal climates are hot and humid. These regions have a high moisture index and support rich vegetation all year. Megathermal climates include the Amazon Basin; many islands in Southeast Asia, such as New Guinea and the Philippines; and the Congo Basin in Africa.
     
    Köppen Classification System
    Although many climatologists think the Thornthwaite system is an efficient, rigorous way of classifying climate, it is complex and mapping it is difficult. The system is rarely used outside scientific publishing.
     
    The most popular system of classifying climates was proposed in 1900 by Russian-German scientist Wladimir Köppen. Köppen observed that the type of vegetation in a region depended largely on climate. Studying vegetation, temperature, and precipitation data, he and other scientists developed a system for naming climate regions. 
     
    According to the Köppen climate classification system, there are five climate groups: tropical, dry, mild, continental, and polar. These climate groups are further divided into climate types. The following list shows the climate groups and their types:
     
    Tropical
    Wet (rain forest)
    Monsoon
    Wet and dry (savanna)
    Dry
    Arid
    Semiarid
    Mild
    Mediterranean
    Humid subtropical
    Marine
    Continental
    Warm summer
    Cool summer
    Subarctic (boreal)
    Polar
    Tundra
    Ice cap
     
     
     
    There are three climate types in the tropical group: tropical wet; tropical monsoon; and tropical wet and dry.
     
    Tropical Wet: Rain Forests
    Places with a tropical wet climate are also known as rain forests. These equatorial regions have the most predictable weather on Earth, with warm temperatures and regular rainfall. Annual rainfall exceeds 150 centimeters (59 inches), and the temperature varies more during a day than it does over a year. The coolest temperature, about 20° to 23° Celsius (68°-73° Fahrenheit), occurs just before dawn. Afternoon temperatures usually reach 30° to 33° Celsius (86°-91° Fahrenheit). Rain forests experience very little seasonal change, meaning average monthly temperatures remain fairly constant throughout the year.
     
    Tropical wet climates exist in a band extending about 10° of latitude on either side of the Equator. This part of the globe is always under the influence of the intertropical convergence zone (ITCZ). The ITCZ follows a pendulum-like path during the course of a year, moving back and forth across the Equator with the seasons. It moves north during summer in the Northern Hemisphere, and south during the northern winter.
     
    Some tropical wet climates are wet throughout the year. Others experience more rainfall during the summer or winter, but they never have especially dry seasons. The U.S. state of Hawaii; Kuala Lumpur, Malaysia; and Belém, Brazil, are examples of areas with tropical wet climates.
     
    Tropical Monsoon
    Tropical monsoon climates are mostly found in southern Asia and West Africa. A monsoon is a wind system that reverses its direction every six months. Monsoons usually flow from sea to land in the summer, and from land to sea in the winter. 
     
    Summer monsoons bring large amounts of rainfall to tropical monsoon regions. People living in these regions depend on the seasonal rains to bring water to their crops. India and Bangladesh are famous for their monsoon climate patterns.
     
    Tropical Wet and Dry: Savanna
    Tropical wet and dry climates are sometimes called “savanna” climates after the grassland ecosystem defined by wet and dry periods.
     
    Tropical wet and dry climates sit just outside the ITCZ, near the Equator. They have three seasons. One season is cool and dry—when the warm, moist ITCZ is in the opposite hemisphere. Another season is hot and dry as the ITCZ approaches. The last season is hot and wet as the ITCZ arrives and the region experiences months as a tropical wet climate. 
     
    Life in these tropical wet and dry regions depends on the wet season’s rains. During years when rains are light, people and animals suffer through drought. During especially rainy years, regions may experience flooding. Havana, Cuba; Kolkata, India; and Africa’s vast Serengeti Plain are in the wet and dry tropics.
     
    Dry Climates
     
    Regions lying within the dry climate group occur where precipitation is low. There are two dry climate types: arid and semiarid. Most arid climates receive 10 to 30 centimeters (4 to 12 inches) of rain each year, and semiarid climates receive enough to support extensive grasslands. 
    Temperatures in both arid and semiarid climates show large daily and seasonal variations. The hottest spots in the world are in arid climates. The temperature in the arid North African town of El Aziza, Libya, reached 58° Celsius (136° Fahrenheit) on September 13, 1922—the highest weather temperature ever recorded.
     
    Although rainfall is limited in all dry climates, there are a few parts of the world where it never rains. One of the driest places on Earth is the Atacama Desert of Chile, on the west coast of South America. Stretches of the Atacama have never received rain in recorded history.
     
    Semiarid regions, such as the Australian Outback, usually receive between 25 and 50 centimeters (10-20 inches) of rainfall every year. They are often located between arid and tropical climate regions.
     
    Arid and semiarid climates can occur where the movement of warm, moist air is blocked by mountains. Denver, Colorado, just east of the Rocky Mountains in the U.S., has this type of dry climate, known as a “rain shadow.”
     
    Mild Climates 
     
    Regions with mild and continental climates are also called temperate regions. Both climate types have distinct cold seasons. In these parts of the world, climate is influenced mostly by latitude and a region’s position on the continent. 
     
    Mediterranean
    Mediterranean climates have warm summers and short, mild, rainy winters. Mediterranean climates are found on the west coasts of continents between 30° and 40° latitude, and along the shores of the Mediterranean Sea. 
     
    Mediterranean summers feature clear skies, cool nights, and little rain. The city of Jerusalem, Israel, once had no rain in July for more than 100 years. 
     
    Humid Subtropical
    Humid subtropical climates are usually found on the eastern sides of continents. In cities such as Savannah, Georgia, in the U.S.; Shanghai, China; and Sydney, Australia, summers are hot and humid. Winter can be severely cold. Precipitation is spread evenly through the year and totals 76 to 165 centimeters (30-65 inches). Hurricanes and other violent storms are common in these regions.
     
    Marine West Coast
    Weather on both sides of a continent generally becomes cooler as latitude increases. 
     
    The marine west coast climate, a type of mild climate typical of cities such as Seattle, Washington, in the U.S. and Wellington, New Zealand, has a longer, cooler winter than the Mediterranean climate. Drizzle falls about two-thirds of winter days, and temperatures average about 5° Celsius (41° Fahrenheit). 
     
    Continental Climates
     
    Areas with continental climates have colder winters, longer-lasting snow, and shorter growing seasons. They are the transition zones between mild and polar climates. Continental climates experience extreme seasonal changes.
     
    The range of weather in continental climate regions makes them among the most spectacular sites for weather phenomena. In autumn, for instance, vast forests put on their annual show of brilliant color before shedding their leaves as winter approaches. Thunderstorms and tornadoes, among the most powerful forces in nature, form mostly in continental climates.
     
    There are three types of continental climate—warm summer, cool summer, and subarctic. All these climates exist only in the Northern Hemisphere. Usually, continental climates are found in the interior of continents.
     
    Warm Summer
    Warm summer climate regions often have wet summer seasons, similar to monsoon climates. For this reason, this climate type is also called humid continental. Most of Eastern Europe, including Romania and Georgia, has warm summer climates.
     
    Cool Summer
    Cool summer climates have winters with low temperatures and snow. Cold winds, sweeping in from the Arctic, dominate winter weather. 
     
    People living in these climates have grown accustomed to the harsh weather, but those unprepared for such cold may suffer. Many of Napoleon Bonaparte’s soldiers, for example, were used to the mild Mediterranean climates of France. Thousands died in bitter cold as they retreated from Russia’s cool summer climate in the winter of 1812.
     
    Subarctic
    North of regions with cool summer climates are regions with subarctic climates. These regions, including northern Scandinavia and Siberia, experience very long, cold winters with little precipitation. Subarctic climates are also called boreal climates or taiga.
     
    Polar Climates
     
    The two polar climate types, tundra and ice cap, lie within the Arctic and Antarctic Circles near the North and South Poles. 
     
    Tundra
    In tundra climates, summers are short, but plants and animals are plentiful. Temperatures can average as high as 10° Celsius (50° Fahrenheit) in July. Wildflowers dot the landscape, and flocks of migratory birds feed on insects and fish. Whales feed on microscopic creatures in the region’s cold, nutrient-rich waters. People have adapted to life on the tundra for thousands of years. 
     
    Ice Cap
    Few organisms survive in the ice cap climates of the Arctic and Antarctic. Temperatures rarely rise above freezing, even in summer. The ever-present ice helps keep the weather cold by reflecting most of the Sun’s energy back into the atmosphere. Skies are mostly clear and precipitation is low. In fact, Antarctica, covered by an ice cap a mile thick, is one of the largest, driest deserts on Earth.
     
    High Elevation Climates
     
    Many geographers and climatologists have modified the Köppen classification system over the years, including geographer Glen Trewartha, who added a category for high-elevation climates.
     
    There are two high elevation climate types: upland and highland. Upland climates occur on high plateaus, or flat-topped mountains. The Patagonian Plateau, in southern South America, has an upland climate. 
     
    Highland climates occur on mountains. 
     
    Both highland and upland climates are marked by very different temperatures and levels of precipitation. Climbing a lofty mountain or reaching a plateau can be like moving toward the poles. On some mountains, such as Mount Kilimanjaro, Tanzania, the climate is tropical at the base and polar at the summit. Often, high-elevation climate differs from one side of the mountain to the other.
     
    Influence of Climate
     
    The enormous variety of life on Earth is largely due to the variety of climates that exist and the climate changes that have occurred in the past.
     
    Climate has influenced the development of cultures and civilizations. People everywhere have adapted in various ways to the climates in which they live. 
     
    Clothing
    Clothing, for example, is influenced by climate. Indigenous Arctic cultures of Europe, Asia, and North America, for example, developed warm, durable, fur and animal-skin clothing. This clothing was necessary for survival in the icy climate near the North Pole. Many parkas worn by Arctic peoples are not only insulated, but waterproof. This combats both the frigid temperatures and precipitation found in polar climates.
     
    Lightweight, papery tapa cloth, on the other hand, is part of many cultures in the warm, humid climates of Polynesia, in the South Pacific Ocean. Tapa cloth was traditionally made from dried leaves, coconut fibers, and breadfruit bark. Tapa cloth is delicate and loses strength when wet, which would be deadly near the poles but only inconvenient near the Equator.
     
    Shelter
    Climate also influences how civilizations construct housing. For instance, the ancient Anasazi people of southern North America built apartments into tall cliffs. The sheltered, shady area kept residents cool in the hot, dry desert climate.  
     
    The yurt is a part of the identity of many cultures across the windy, semi-arid steppe of Central Asia. Yurts are a type of original “mobile home,” a portable, circular dwelling made of a lattice of flexible poles and covered in felt or other fabric. Yurts protect residents from fierce winds, and their portability makes them an ideal structure for nomadic and semi-nomadic herding cultures on the grassland. 
     
    Agriculture
    The development of agriculture was very dependent on climate. Ancient agricultural civilizations, such as those in Mesopotamia and India, flourished where the climate was mild. Communities could grow crops every season, and experiment with different types of crops, livestock, and farming techniques. 
     
    The mild, Mediterranean climate in which the civilization of Ancient Rome developed, for instance, allowed farmers to cultivate crops such as wheat, olives, grapes, barley, and figs. Livestock included cattle, sheep, goats, pigs, and even honeybees.
     
    Like the ancient Romans, ancient cultures of the Amazon basin in South America were also able to develop agricultural practices.  The chief domesticated trees in the Amazon were mostly harvested for food and medicine: Brazil nuts, Inga ynga fruit (commonly known as “ice-cream beans”), Amazon tree grapes, abiu (another tropical fruit), and cacao fruits (whose seeds are known as cocoa beans).
     
    Today, farmers are still in tune with the climate. They plant certain crops according to the expected amount of rainfall and the length of the growing season. When the weather does not follow the typical climate pattern, it can mean hard times for farmers and higher food costs for consumers.
     
    Climate Change
     
    Climate does not change from day to day like weather, but it does change over time. The study of historic climate change is called paleoclimatology.
     
    Climate changes happen slowly over hundreds or even thousands of years. For example, periodic glacial periods have covered large portions of Earth with ice caps. Some paleoclimatology evidence shows that the Sahara Desert was once covered by ocean during a warm “wet age.” 
     
    Climate change can happen for many reasons. The movement of tectonic plates, volcanic activity, and the tilt of Earth’s axis all have effects on climate. For example, after the eruption of the island volcano of Krakatoa, Indonesia, in 1883, winters and even summers in Asia and Europe were colder and darker. Volcanic ash blocked the sun. Farmers had to adjust to shorter, weaker growing seasons. Climates around the world were changed for years. 
     
    The so-called “Little Ice Age” was a period of climate change extending from the 12th through the 19th centuries. The Little Ice Age was not a true glacial period, but describes colder climates around the world. In Europe, canals in Great Britain and the Netherlands were often frozen solid, allowing for ice skating. In North America, European colonists reported especially harsh winters. Even Africa experienced severe changes in temperature and precipitation. Mountain ranges in Ethiopia and Mauritania were permanently snow-capped. The bustling trade city of Timbuktu, Mali, was flooded more than a dozen times by the Niger River, a phenomenon that has not happened since.
     
    Global Warming
    Since the Industrial Revolution of the 19th century, human activity has begun to impact climate. The current period of climate change is sometimes called “global warming.”
     
    Global warming is often associated with a runaway “greenhouse effect.” The greenhouse effect describes the process of certain gases (including carbon dioxide (CO2), methane, nitrous oxide (N2O), fluorinated gases, and ozone) trapping solar radiation in a planet's lower atmosphere. Greenhouse gases let the sun’s light shine onto the Earth’s surface, but they trap the heat that reflects back up into the atmosphere. In this way, they act like the glass walls of a greenhouse.
     
    The greenhouse effect is a natural phenomenon and keeps Earth warm enough to sustain life. However, human activities that include burning fossil fuels and cutting down forests release greenhouse gases into the atmosphere at an unprecedented rate.
     
    The current period of climate change has been documented by rising temperatures, melting glaciers, and more intense weather phenomena. 
     
    Our planet’s temperature has risen about 1.1° C (2° F) since the late 19th century. Sixteen of the last 17 warmest years on record have occurred in the 21st century. According to NASA, not only was 2016 the warmest year on record, but eight of the 12 months that make up the year were the warmest on record for those respective months.
     
    The current period of climate change is also associated with the massive retreat of glaciers, ice sheets, and sea ice. Warmer temperatures have reduced the glaciers of Montana’s Glacier National Park from 150 in 1850 to just 26 today. In 2017, one of the largest icebergs ever recorded entered the ocean as a huge chunk of the Larsen C ice shelf broke off the Antarctic Peninsula. Warmer ocean temperatures and warmer ambient air temperatures likely contributed to the fracturing of the ice shelf and the massive Antarctic ice sheet associated with it. Finally, both the extent and thickness of Arctic sea ice has declined rapidly during the past several decades. The famed Northwest Passage, the treacherous route connecting the North Atlantic and North Pacific ocean basins, is now habitually free of ice and safe enough for cruise ships to navigate.
     
    Melting glaciers and ice sheets, as well as expansion of seawater as it warms, have contributed to unprecedented sea level rise. Sea level rises at about 2.3 millimeters (.2 inch) every year, contributing to up to 900% more frequent flooding in coastal areas.
     
    Increasing temperatures can change the climate impacts and even the classification of a region. For instance, low-lying islands may be flooded as seawater rises. The populations of island nations such as Maldives or Comoros have been forced to contemplate becoming “climate refugees”—people forced to leave their homes and migrate to a different region.  
     
    Heat in the atmosphere may increase the interaction of diverse weather systems. Unusually arid climates in a semi-arid region may prolong droughts, for instance. In regions with mild climates, the increased atmospheric moisture associated with humid climates may increase the likelihood of hurricanes and typhoons.
     
    Climate change is also impacting organisms and species ranges. Organisms that have adapted to one climate may have to migrate or adapt to warmer temperatures. Manatees, for instance, are marine mammals native to tropical waters. As temperatures increase, manatees have been migrating as far north as New York City, New York. Polar bear populations, on the other hand, are venturing further south as Arctic sea ice becomes more scarce.
     
    Climate change can be mitigated through reducing greenhouse-gas emissions. This can mean investing in new technologies, relying more on renewable energy sources, making older equipment more energy-efficient, or changing consumer behavior.
    climate
    Climate influences the vegetation of a region.
    Climograph
    A climograph depicts the highs and lows of temperature and precipitation over a set period of time. Climographs can summarize daily, monthly, yearly, or decades-long weather patterns to help climatologists identify a region’s climate. 
    Did the Language You Speak Evolve Due to Heat?
    Some research indicates that the concentration of a language’s vowels and consonants may be due in some part to the climate of the language’s region. Vowel-heavy languages, such as Hawaiian, may have been influenced by pockets of warm air that can “punch into a sound wave”, making it harder to distinguish consonants such as “k” and “ch.”
    Geographic Perspective
    British geographer Andrew John Herbertson described climate like this: "Climate is what we expect, weather is what we get."

    The Big Chill
    Antarctica’s frigid climate makes it the only continent on Earth with no permanent human residents. The coldest temperature ever recorded at ground level on Earth—-89.2° Celsius (-128.5°Fahrenheit)—was at Vostok Station, Antarctica.

  • Term Part of Speech Definition Encyclopedic Entry
    abundance Noun

    large amount.

    adapt Verb

    to adjust to new surroundings or a new situation.

    adjust Verb

    to change or modify something to fit with something else.

    agriculture Noun

    the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

    Encyclopedic Entry: agriculture
    ambient Adjective

    having to do with the surrounding area or environment.

    Anasazi Noun

    (1200 BCE-1300 CE) people and culture native to what is now the southwestern United States. Also called Ancestral Puebloans.

    ancient Adjective

    very old.

    ancient Rome Noun

    civilization founded on the Mediterranean Sea, lasting from the 8th century BCE to about 476 CE.

    Arctic Noun

    region at Earth's extreme north, encompassed by the Arctic Circle.

    Encyclopedic Entry: Arctic
    arid Adjective

    dry.

    arid climate Noun

    (dry climate) region that receives 10 to 30 centimeters (4-12 inches) of rain each year.

    asphalt Noun

    chemical compound made of dark, solid rocks and minerals often used in paving roads.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    atmospheric pressure Noun

    force per unit area exerted by the mass of the atmosphere as gravity pulls it to Earth.

    Encyclopedic Entry: atmospheric pressure
    axis Noun

    an invisible line around which an object spins.

    Encyclopedic Entry: axis
    basin Noun

    a dip or depression in the surface of the land or ocean floor.

    Encyclopedic Entry: basin
    biodiversity Noun

    all the different kinds of living organisms within a given area.

    Encyclopedic Entry: biodiversity
    biosphere Noun

    part of the Earth where life exists.

    Encyclopedic Entry: biosphere
    boreal climate Adjective

    region that experiences long, cold winters with very little precipitation. Also called a subarctic or tundra climate.

    boreal climate Adjective

    region that experiences long, cold winters with very little precipitation. Also called a subarctic or tundra climate.

    burrow Noun

    small hole or tunnel used for shelter.

    canal Noun

    artificial waterway.

    carbon sink Noun

    area or ecosystem that absorbs more carbon dioxide than it releases.

    civilization Noun

    complex way of life that developed as humans began to develop urban settlements.

    Encyclopedic Entry: civilization
    classify Verb

    to identify or arrange by specific type or characteristic.

    cliff Noun

    steep wall of rock, earth, or ice.

    Encyclopedic Entry: cliff
    climate Noun

    all weather conditions for a given location over a period of time.

    Encyclopedic Entry: climate
    climate change Noun

    gradual changes in all the interconnected weather elements on our planet.

    Encyclopedic Entry: climate change
    climate group Noun

    one of five classifications of the Earth's climates: tropical, dry, mild, continental, and polar.

    climate refugee Noun

    person forced to leave his or her home and community because of climate change.

    Encyclopedic Entry: climate refugee
    climate type Noun

    division within a climate group.

    climatologist Noun

    person who studies long-term patterns in weather.

    cloud cover Noun

    amount of sky covered with clouds.

    complex Adjective

    complicated.

    coniferous forest Noun

    land covered by trees with thin needles instead of flat leaves.

    continent Noun

    one of the seven main land masses on Earth.

    Encyclopedic Entry: continent
    continental climate Noun

    climate group that experiences extreme seasonal change. Continental climates are only found in the Northern Hemisphere.

    cool summer climate Noun

    region that experience cool summers and snowy winters.

    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    cryosphere Noun

    icy part of the Earth's waterincluding icebergs, glaciers, and ice caps.

    cultivate Verb

    to encourage the growth of something through work and attention.

    culture Noun

    learned behavior of people, including their languages, belief systems, social structures, institutions, and material goods.

    dam Noun

    structure built across a river or other waterway to control the flow of water.

    data Plural Noun

    (singular: datum) information collected during a scientific study.

    delicate Adjective

    fragile or easily damaged.

    desert Noun

    area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

    Encyclopedic Entry: desert
    drizzle Noun

    very light rain.

    drought Noun

    period of greatly reduced precipitation.

    Encyclopedic Entry: drought
    drought Noun

    period of greatly reduced precipitation.

    Encyclopedic Entry: drought
    dry Adjective

    arid or lacking in moisture.

    dry season Noun

    time of year with little precipitation.

    durable Adjective

    strong and long-lasting.

    ecosystem Noun

    community and interactions of living and nonliving things in an area.

    Encyclopedic Entry: ecosystem
    efficient Adjective

    performing a task with skill and minimal waste.

    elevation Noun

    height above or below sea level.

    Encyclopedic Entry: elevation
    emission Noun

    discharge or release.

    enormous Adjective

    very large.

    Equator Noun

    imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude.

    Encyclopedic Entry: equator
    erosion Noun

    act in which earth is worn away, often by water, wind, or ice.

    Encyclopedic Entry: erosion
    eruption Noun

    release of material from an opening in the Earth's crust.

    evaporation Noun

    process by which liquid water becomes water vapor.

    Encyclopedic Entry: evaporation
    evapotranspiration Noun

    loss of water from the Earth's soil by evaporation into the atmosphere and transpiration by plants.

    farming Noun

    the art, science, and business of cultivating the land for growing crops.

    flood Verb

    to overflow or cover in water or another liquid.

    flourish Verb

    to thrive or be successful.

    fog Noun

    clouds at ground level.

    Encyclopedic Entry: fog
    forest Noun

    ecosystem filled with trees and underbrush.

    fossil fuel Noun

    coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals.

    freshwater Adjective

    having to do with a habitat or ecosystem of a lake, river, or spring.

    frigid Adjective

    very cold.

    gas Noun

    state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.

    geographer Noun

    person who studies places and the relationships between people and their environments.

    geologic Adjective

    having to do with the physical formations of the Earth.

    glacial period Noun

    time of long-term lowering of temperatures on Earth. Also known as an ice age.

    glacier Noun

    mass of ice that moves slowly over land.

    Encyclopedic Entry: glacier
    global warming Noun

    increase in the average temperature of the Earth's air and oceans.

    Encyclopedic Entry: global warming
    grassland Noun

    ecosystem with large, flat areas of grasses.

    Great Lakes Noun

    largest freshwater bodies in the world, located in the United States and Canada. Lake Huron, Lake Ontario, Lake Michigan, Lake Erie, and Lake Superior make up the Great Lakes.

    greenhouse effect Noun

    phenomenon where gases allow sunlight to enter Earth's atmosphere but make it difficult for heat to escape.

    Encyclopedic Entry: greenhouse effect
    greenhouse gas Noun

    gas in the atmosphere, such as carbon dioxide, methane, water vapor, and ozone, that absorbs solar heat reflected by the surface of the Earth, warming the atmosphere.

    growing season Noun

    period in the year when crops and other plants grow rapidly.

    harvest Noun

    the gathering and collection of crops, including both plants and animals.

    herding Noun

    practice of caring for roaming groups of livestock over a large area.

    Encyclopedic Entry: herding
    heritage Noun

    cultural or family background.

    high-elevation climate Noun

    climate group found in mountains and plateaus.

    humid continental Noun

    (continental climate) region that experiences cold winters and warm, wet summers. Also called a warm summer climate.

    humidity Noun

    amount of water vapor in the air.

    Encyclopedic Entry: humidity
    humid subtropical climate Noun

    region that experiences cool winters and hot humid summers.

    hurricane Noun

    tropical storm with wind speeds of at least 119 kilometers (74 miles) per hour. Hurricanes are the same thing as typhoons, but usually located in the Atlantic Ocean region.

    hydrosphere Noun

    all the Earth's water in the ground, on the surface, and in the air.

    Encyclopedic Entry: hydrosphere
    iceberg Noun

    large chunks of ice that break off from glaciers and float in the ocean.

    Encyclopedic Entry: iceberg
    ice cap climate Noun

    region where temperatures rarely rise above freezing.

    ice sheet Noun

    thick layer of glacial ice that covers a large area of land.

    Encyclopedic Entry: ice sheet
    ice shelf Noun

    mass of ice that floats on the ocean but remains attached to the coast.

    inconvenience Verb

    to disturb or bother.

    indigenous Adjective

    characteristic to or of a specific place.

    Encyclopedic Entry: indigenous
    Industrial Revolution Noun

    change in economic and social activities, beginning in the 18th century, brought by the replacement of hand tools with machinery and mass production.

    influence Verb

    to encourage or persuade a person or organization to act a certain way.

    insulate Verb

    to cover with material to prevent the escape of energy (such as heat) or sound.

    interaction Noun

    relationship between two or more forces, objects, or organisms.

    Intertropical Convergence Zone (ITCZ) Noun

    belt of low-pressure air currents that circle the Earth at the Equator. Also known as the Monsoon Zone.

    lake effect Noun

    process where cold winds blowing over a relatively warm lake cause rapid cloud formation and precipitation.

    land cover Noun

    physical material at the very top surface of the Earth, such as grass.

    landscape Noun

    the geographic features of a region.

    Encyclopedic Entry: landscape
    latitude Noun

    distance north or south of the Equator, measured in degrees.

    Encyclopedic Entry: latitude
    lattice Noun

    strips of wood or other material assembled in a crisscross pattern.

    Little Ice Age Noun

    (~1600-~1850) period of cooling climate (~1° Celsius), documented largely in the Northern Hemisphere.

    livestock noun, plural noun

    animals raised for sale and profit.

    marine Adjective

    having to do with the ocean.

    marine mammal Noun

    an animal that lives most of its life in the ocean but breathes air and gives birth to live young, such as whales and seals.

    marine west coast climate Noun

    (mild climate) region that experiences rain and long, cool winters.

    medicine Noun

    substance used for treating illness or disease.

    Mediterranean climate Noun

    (mild climate) region that experiences mild winters and warm summers.

    megathermal Adjective

    climate pattern characterized by high temperatures and abundant moisture.

    Mesopotamia Noun

    ancient region between the Tigris and Euphrates Rivers, today lying mostly in Iraq.

    mesothermal Adjective

    climate characterized by a moderate amount of heat.

    microclimate Noun

    small area where the climate differs within a larger climate region, such as "heat islands" in a city.

    microscopic Adjective

    very small.

    microthermal Adjective

    climate characterized by cold winters.

    migrate Verb

    to move from one place or activity to another.

    mild climate Noun

    climate group that experiences seasonal temperature changes. Also called a temperate climate.

    mitigate Verb

    to lower the severity of a natural or human condition.

    moisture index Noun

    method for monitoring soil’s water budget, based on the concept of potential evapotranspiration.

    monsoon Noun

    seasonal change in the direction of the prevailing winds of a region. Monsoon usually refers to the winds of the Indian Ocean and South Asia, which often bring heavy rains.

    Encyclopedic Entry: monsoon
    mound Noun

    hill built by people.

    navigate Verb

    to plan and direct the course of a journey.

    Northwest Passage Noun

    waterway connecting the Atlantic and Pacific Oceans.

    nutrient Noun

    substance an organism needs for energy, growth, and life.

    Encyclopedic Entry: nutrient
    ocean basin Noun

    depression in the Earth's surface located entirely beneath the ocean.

    Outback Noun

    remote, sparsely populated interior region of Australia.

    paleoclimatology Noun

    study of the atmosphere of prehistoric Earth.

    Pampas Noun

    flat grasslands of South America.

    parka Noun

    hip-length, waterproof winter coat with a hood.

    pendulum Noun

    object suspended from a point, able to swing back and forth.

    periodic Adjective

    occasional.

    permafrost Noun

    permanently frozen layer of the Earth's surface.

    Encyclopedic Entry: permafrost
    phenomena Plural Noun

    (singular: phenomenon) any observable occurrence or feature.

    photosynthesis Noun

    process by which plants turn water, sunlight, and carbon dioxide into water, oxygen, and simple sugars.

    plateau Noun

    large region that is higher than the surrounding area and relatively flat.

    Encyclopedic Entry: plateau
    polar Adjective

    having to do with the North and/or South Pole.

    polar climate Noun

    climate group found within the Arctic and Antarctic Circles.

    pole Noun

    extreme north or south point of the Earth's axis.

    Polynesia Noun

    island group in the Pacific Ocean between New Zealand, Hawaii, and Easter Island.

    portable Adjective

    able to be easily transported from one place to another.

    potential evapotranspiration Noun

    amount of water evaporated from an area of continuous, uniform vegetation that covers the whole ground and that is well supplied with water.

    precipitation Noun

    all forms in which water falls to Earth from the atmosphere.

    Encyclopedic Entry: precipitation
    predictable Adjective

    regular or able to be forecasted.

    prolong Verb

    to extend the duration of something.

    proximity Noun

    nearness.

    rain forest Noun

    area of tall, mostly evergreen trees and a high amount of rainfall.

    Encyclopedic Entry: Rain forest
    rain shadow Noun

    dry land on the side of a mountain facing away from prevailing winds.

    Encyclopedic Entry: rain shadow
    rainy season Noun

    time of year when most of the rain in a region falls.

    region Noun

    any area on Earth with one or more common characteristics. Regions are the basic units of geography.

    Encyclopedic Entry: region
    renewable energy Noun

    energy obtained from sources that are virtually inexhaustible and replenish naturally over small time scales relative to the human life span.

    retreat Verb

    to go back to a familiar or safe place.

    rigorous Adjective

    demanding, disciplined, or harsh.

    salinity Noun

    saltiness.

    sand Noun

    small, loose grains of disintegrated rocks.

    savanna Noun

    type of tropical grassland with scattered trees.

    Scandinavia Noun

    region and name for some countries in Northern Europe: Iceland, Norway, Sweden, Finland, and Denmark.

    scarce Adjective

    rare.

    sea level rise Noun

    increase in the average reach of the ocean. The current sea level rise is 1.8 millimeters (.07 inch) per year.

    seasonal Adjective

    likely to change with the seasons.

    seawater Noun

    salty water from an ocean or sea.

    semiarid climate Noun

    (dry climate) region that receives between 25 and 50 centimeters (10-20 inches) of rainfall every year.

    semi-nomadic Adjective

    people or communities who follow their food source for long periods of time, but can also live settled lives.

    Siberia Noun

    region of land stretching across Russia from the Ural Mountains to the Pacific Ocean.

    soil Noun

    top layer of the Earth's surface where plants can grow.

    solar radiation Noun

    light and heat from the sun.

    species range Noun

    native, geographic area in which an organism can be found. Range also refers to the geographic distribution of a particular species.

    Encyclopedic Entry: species range
    spectacular Adjective

    dramatic and impressive.

    steppe Noun

    dry, flat grassland with no trees and a cool climate.

    Encyclopedic Entry: steppe
    subarctic climate Noun

    region that experiences long, cold winters with very little precipitation. Also called a boreal or tundra climate.

    taiga Noun

    evergreen forest in cool, northern latitudes. Also called boreal forest.

    Encyclopedic Entry: taiga
    tapa cloth Noun

    lightweight cloth made by pounding the bark of the paper mulberry tree.

    technique Noun

    method of doing something.

    tectonic plate Noun

    massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate.

    temperate Adjective

    moderate.

    temperature Noun

    degree of hotness or coldness measured by a thermometer with a numerical scale.

    Encyclopedic Entry: temperature
    temperature Noun

    degree of hotness or coldness measured by a thermometer with a numerical scale.

    Encyclopedic Entry: temperature
    thermal conductivity Noun

    measure of the ability of a material to transfer heat.

    thermohaline circulation Noun

    ocean conveyor belt system in which water moves between the cold depths and warm surface in oceans throughout the world.

    thunderstorm Noun

    cloud that produces thunder and lightning, often accompanied by heavy rains.

    topography Noun

    study of the shape of the surface features of an area.

    topography Noun

    study of the shape of the surface features of an area.

    tornado Noun

    a violently rotating column of air that forms at the bottom of a cloud and touches the ground.

    trade wind Noun

    winds that blow toward the Equator, from northeast to southwest in the Northern Hemisphere and from southeast to northwest in the Southern Hemisphere.

    transition zone Noun

    area between two natural or artificial regions.

    treacherous Adjective

    very dangerous.

    tropical climate Noun

    climate group that experiences hot, wet summers.

    tropical monsoon climate Noun

    region that experiences the monsoon winds, which bring heavy rain.

    tropical wet and dry climate Noun

    region that experiences three seasons: cool, hot, and wet.

    tropical wet climate Noun

    region that experiences hot temperatures and heavy rainfall all year. Also called a rain forest climate.

    tropics Plural Noun

    region generally located between the Tropic of Cancer (23 1/2 degrees north of the Equator) and the Tropic of Capricorn (23 1/2 degrees south of the Equator).

    Encyclopedic Entry: tropics
    tundra climate Noun

    region that experiences short summers and long winters.

    typhoon Noun

    tropical storm with wind speeds of at least 74 miles (119 kilometers) per hour. Typhoons are the same thing as hurricanes, but usually located in the Pacific or Indian Ocean region.

    uniform Adjective

    exactly the same in some way.

    unprecedented Adjective

    never before known or experienced.

    upland climate Noun

    (high-elevation climate) region found on and around large plateaus.

    urban area Noun

    developed, densely populated area where most inhabitants have nonagricultural jobs.

    Encyclopedic Entry: urban area
    urban heat island Noun

    city area that is always warmer than the surrounding area.

    Encyclopedic Entry: urban heat island
    variation Noun

    difference.

    vegetation Noun

    all the plant life of a specific place.

    volcanic ash Noun

    fragments of lava less than 2 millimeters across.

    Encyclopedic Entry: volcanic ash
    volcano Noun

    an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

    Encyclopedic Entry: volcano
    warm summer climate Noun

    region that experiences cool winters and warm, wet summers. Also called a humid continental climate.

    water budget Noun

    budget of the incoming and outgoing water from a region, including rainfall, evaporation, runoff, and seepage; often used to estimate evapotranspiration.

    weather Noun

    state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.

    Encyclopedic Entry: weather
    weather pattern Noun

    repeating or predictable changes in the Earth's atmosphere, such as winds, precipitation, and temperatures.

    weather system Noun

    movement of warm or cold air.

    wind Noun

    movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

    yurt Noun

    portable circular dwelling made of a criss-crossed wooden frame covered in felt and popular in Central Asia.

    Encyclopedic Entry: yurt