Climate – Definition, Types, Classification, and Examples   Recently updated !

Climate is the long-term pattern of weather conditions in a place, region, or across Earth as a whole. It describes not only average temperature and precipitation, but also seasonal patterns, variability, extremes, and the frequency of different weather conditions over years to decades or longer.

For example, describing a region as having hot, humid summers and mild winters is a statement about climate. Saying that tomorrow will be hot with afternoon thunderstorms is a statement about weather.

Scientists often use 30-year periods called climate normals to describe and compare climate. However, climate is more than a 30-year average. It includes the entire statistical pattern of weather, including typical conditions, seasonal cycles, year-to-year variations, unusual events, and long-term trends.

Key Takeaways: Climate

• Climate is the long-term pattern of weather, including averages, variability, seasonal cycles, and extremes.
• Weather describes short-term atmospheric conditions, while climate describes patterns over much longer periods.
• Important climate variables include temperature, precipitation, humidity, wind, atmospheric pressure, cloud cover, solar radiation, and snow and ice.
• A region’s climate depends on factors including latitude, elevation, proximity to water, ocean currents, topography, atmospheric circulation, and land cover.
• The Köppen-Geiger system classifies most climates into tropical, dry, temperate, continental, and polar groups.
• Climate variability refers to fluctuations around typical conditions, while climate change is a persistent shift in climate over decades or longer.
• Scientists study climate using observations, climate models, and evidence of ancient climates preserved in tree rings, ice, sediments, corals, and other natural archives.

Why Understanding Climate Is Important

Climate influences nearly every part of the Earth system. It helps determine where ecosystems occur, which crops grow successfully, how much water is available, where glaciers form, and how landscapes develop.

Knowledge of climate has practical importance for:

• Agriculture: Farmers select crops and planting schedules based partly on temperature, rainfall, frost risk, and growing-season length.
• Water resources: Climate affects rainfall, snowfall, evaporation, groundwater recharge, drought, and streamflow.
• Ecosystems: Temperature and moisture strongly influence the distribution of plants, animals, and biomes.
• Human health: Climate influences heat stress, cold exposure, air quality, disease vectors, allergens, and some infectious diseases.
• Buildings and infrastructure: Engineers consider temperature extremes, snow loads, flooding, drought, wind, and other climate-related risks.
• Energy: Climate affects heating and cooling demand as well as the availability of solar, wind, and hydroelectric power.
• Transportation: Snow, ice, flooding, sea level, heat, and storms affect roads, airports, ports, and railways.
• Natural hazards: Climate helps establish the background conditions in which droughts, wildfires, floods, heat waves, and other hazards occur.

Understanding climate also provides the baseline needed for recognizing climate variability and climate change.

History of Climate and Climatology

People have recognized regional differences in climate since ancient times. Agriculture, navigation, settlement, and trade all depended on understanding seasonal temperature and rainfall patterns long before scientists had instruments for measuring them.

Ancient Ideas About Climate

The word climate traces back through French and Latin to the Greek word klima, meaning an inclination or slope. The original idea referred to the inclination of sunlight and the way conditions changed with latitude.

Ancient Greek geographers divided the known world into climatic belts based partly on latitude, the angle of the Sun, and the length of daylight. Climate therefore originally referred more to a geographic zone than to its weather.

Greek thinkers such as Aristotle discussed atmospheric phenomena in works such as Meteorologica during the fourth century BCE. Although many early explanations were incorrect by modern standards, these writings helped establish weather and climate as subjects for systematic study.

Instruments and Climate Records

The development of meteorological instruments during the 17th and 18th centuries transformed climatology. Thermometers, barometers, rain gauges, hygrometers, and later anemometers allowed observers to replace qualitative descriptions with numerical measurements.

Long observational records gradually revealed seasonal cycles, regional differences, and unusual climatic periods.

In the early 19th century, Alexander von Humboldt helped establish modern geographical climatology. He compared measurements from different regions and introduced maps using isotherms, lines connecting locations with the same temperature. These maps made large-scale climate patterns much easier to visualize.

Around the same period, Luke Howard recorded weather conditions in and around London and recognized that the city was warmer than its surroundings, an early description of what is now called the urban heat island effect.

Modern Climate Classification

Russian-German scientist Wladimir Köppen combined climatology with botany and biogeography. Beginning in the late 19th century, he developed a climate classification based primarily on temperature, precipitation, seasonality, and their relationship to vegetation.

Köppen published an early classification in 1884 and revised his system repeatedly. Later work by climatologist Rudolf Geiger contributed to the modern Köppen-Geiger climate classification, which remains widely used.

Other systems followed. For example, climatologist C. W. Thornthwaite developed a classification emphasizing precipitation, evaporation, and water balance.

Climate as a Physical Science

Scientists also began investigating why climates change.

In the 19th century, Joseph Fourier, Eunice Foote, John Tyndall, and Svante Arrhenius contributed to understanding the role of the atmosphere and greenhouse gases in Earth’s temperature.

During the early 20th century, Milutin Milankovitch calculated how slow changes in Earth’s orbit and axial orientation alter the distribution of incoming solar radiation. These orbital variations help explain the timing of glacial and interglacial periods.

During the 20th and 21st centuries, climatology expanded through worldwide weather networks, radiosondes, ocean measurements, satellites, computers, ice cores, sediment cores, and numerical climate models.

Modern climatology combines meteorology, physics, chemistry, geology, oceanography, astronomy, biology, mathematics, and computer science.

Climate Definition

Climate is the statistical description of weather conditions over a long period of time.

It includes quantities such as:

• Average temperature
• Temperature range
• Total precipitation
• Seasonal rainfall or snowfall
• Humidity
• Wind patterns
• Cloudiness
• Sunshine and solar radiation
• Frequency of extremes
• Year-to-year variability
• Long-term trends

Climate can describe a very small area, a region, a continent, or the entire planet.

An important point is that climate is not simply average weather. Two places could have the same average annual temperature while having very different climates. One might have hot summers and cold winters, while another has mild temperatures throughout the year.

Similarly, two locations receiving the same annual rainfall may differ dramatically if one receives rain throughout the year while the other has distinct wet and dry seasons.

For this reason, climatologists examine distributions, ranges, seasonal patterns, extremes, and variability as well as averages.

Climate Normals

A climate normal is an average or other statistical measure calculated over a standardized period, usually 30 years.

For example, a climatologist may calculate the average January temperature for a location using every January during a 30-year reference period.

Climate normals provide a baseline for comparing present conditions with typical conditions.

The World Meteorological Organization uses consecutive 30-year periods for climatological standard normals. The current standard period is 1991-2020. Older periods are still useful for particular applications and for studying long-term change.

A 30-year normal does not mean climate only exists on a 30-year time scale. Researchers investigate climate over periods ranging from seasons and decades to millions of years.

Climate vs Weather

Weather and climate describe related phenomena at different time scales.

A single cold day does not demonstrate that a climate is cooling, just as one unusually hot day does not by itself demonstrate long-term warming.

Individual weather events occur within the larger statistical background established by climate.

Variables Used to Describe Climate

Scientists use several measurable variables, sometimes called climate elements, to describe climate.

Temperature

Temperature is one of the most important climate variables.

Climatologists examine:

• Daily maximum and minimum temperature
• Monthly and annual means
• Seasonal temperature
• Diurnal temperature range
• Annual temperature range
• Frost dates
• Heat waves and cold spells
• Record highs and lows

Temperature strongly influences evaporation, snow and ice, ecosystems, agriculture, and energy use.

Precipitation

Precipitation includes rain, snow, sleet, and other forms of water falling from the atmosphere.

Important properties include:

• Annual precipitation
• Monthly precipitation
• Seasonal distribution
• Rainfall intensity
• Frequency of precipitation
• Duration of wet and dry periods
• Snowfall and snowpack

The timing of precipitation can be as important as its total amount.

Humidity

Humidity describes water vapor in the atmosphere.

Climatologists may use relative humidity, specific humidity, vapor pressure, or dew point. Humidity affects cloud formation, precipitation, evaporation, plant water loss, and human comfort.

Atmospheric Pressure

Atmospheric pressure reflects the weight of the air above a location.

Persistent pressure patterns help control winds, storm tracks, monsoons, and precipitation. Large-scale pressure systems are therefore an important part of regional climate.

Wind

Climate includes characteristic wind speed, wind direction, and seasonal circulation patterns.

Examples include:

• Trade winds
• Westerlies
• Monsoon circulations
• Sea breezes
• Mountain and valley winds

Wind transports heat and moisture from one region to another.

Cloud Cover and Sunshine

Clouds influence both incoming sunlight and outgoing infrared radiation.

Climatologists therefore examine:

• Cloud frequency
• Cloud type
• Sunshine duration
• Solar radiation

Cloudiness helps explain why locations with similar latitude may still have different temperature patterns.

Snow and Ice

Snow cover, glaciers, sea ice, and frozen ground are important climate variables, particularly at high latitudes and elevations.

Also, snow and ice affect climate because their bright surfaces reflect a large fraction of incoming sunlight.

Evaporation and Evapotranspiration

Evaporation transfers water from surfaces into the atmosphere. Evapotranspiration combines evaporation with water released by plants.

These processes are especially useful for evaluating water availability and distinguishing humid climates from dry ones.

Ocean Variables

Because the atmosphere and ocean exchange enormous quantities of heat, water, and gases, ocean conditions are also important to climate.

Relevant variables include:

• Sea-surface temperature
• Ocean heat content
• Sea ice
• Salinity
• Currents
• Sea level

What Determines the Climate of a Place?

Climate variables describe climate, while climate controls help explain why the climate has particular characteristics.

Latitude

Latitude affects the angle and seasonal distribution of incoming sunlight.

Equatorial regions generally receive more direct sunlight throughout the year, while high latitudes receive sunlight at lower angles and experience greater seasonal changes in day length.

Elevation

Air temperature generally decreases with increasing altitude in the lower atmosphere. As a result, mountains often have cooler climates than nearby lowlands at the same latitude.

Distance From the Ocean

Water heats and cools more slowly than land.

Coastal locations therefore often experience smaller temperature ranges than locations deep within continents. Continental interiors commonly have hotter summers, colder winters, or both.

Ocean Currents

Ocean currents redistribute heat.

Warm currents can make nearby coastal regions warmer and more humid, while cold currents may cool coastlines and contribute to dry climates.

Atmospheric Circulation

Global wind belts, pressure systems, jet streams, and air masses transport heat and moisture around the planet.

Their positions help determine deserts, rainy tropical regions, monsoons, and mid-latitude storm tracks.

Topography

Mountains strongly affect local and regional climate.

Moist air rising over a mountain cools and can produce precipitation on the windward side. Descending air on the leeward side becomes warmer and drier, producing a rain shadow.

Slope direction also matters because slopes receiving more sunlight are generally warmer and drier than shaded slopes.

Land Cover and Vegetation

Forests, grasslands, deserts, wetlands, farms, and cities interact differently with solar radiation and water.

Vegetation influences evaporation, shade, wind, soil moisture, and carbon exchange. Removing or changing vegetation can therefore influence local and regional climate.

Snow and Ice

Bright snow and ice reflect much more sunlight than darker land or water. Changes in snow and ice cover therefore influence Earth’s energy balance.

Atmospheric Composition

Greenhouse gases, aerosols, water vapor, clouds, and airborne particles affect how energy enters, leaves, and moves through the climate system.

Volcanic Eruptions

Large explosive volcanic eruptions can inject sulfur-containing gases into the stratosphere. The resulting sulfate aerosols reflect sunlight and can temporarily cool global climate.

Solar and Orbital Changes

Changes in solar output can influence climate.

Over much longer periods, variations in Earth’s orbit, axial tilt, and precession alter the geographic and seasonal distribution of sunlight. These Milankovitch cycles play an important role in glacial-interglacial cycles.

Climate Classification

A climate classification system groups regions with similar long-term climatic characteristics.

Classification makes it easier to compare locations, map climate zones, study ecosystems, and identify broad geographic patterns.

Several classification systems exist, but the Köppen-Geiger system is the best known.

Köppen Climate Classification

The Köppen-Geiger system primarily uses temperature and precipitation, including their seasonal distribution. Its boundaries were designed in part to correspond with major vegetation zones.

The system has five main climate groups.

Letters added to the major group indicate precipitation seasonality and temperature characteristics.

For example:

• Af: Tropical rainforest
• Aw: Tropical savanna
• BWh: Hot desert
• BSk: Cold semi-arid steppe
• Csa: Hot-summer Mediterranean
• Cfa: Humid subtropical
• Cfb: Marine west coast or oceanic
• Dfa: Hot-summer humid continental
• Dfc: Subarctic
• ET: Tundra
• EF: Ice cap

Some educational maps add H for highland climates, but highland is not one of the five standard Köppen major groups.

Climate boundaries are not sharp natural walls. Conditions gradually change across landscapes, and classifications may differ slightly depending on the data set, reference period, and exact version of the system.

Other Climate Classification Systems

Köppen is not the only way to classify climate.

Thornthwaite Classification

The Thornthwaite system emphasizes water balance and potential evapotranspiration. It is particularly useful for hydrology, agriculture, and studies of water availability.

Trewartha Classification

The Trewartha climate classification modifies the Köppen system, especially in the middle latitudes. One goal is to make climatic regions correspond more closely to vegetation patterns.

Holdridge Life Zones

The Holdridge life zone system relates temperature, precipitation, and potential evapotranspiration to ecological zones.

Different classification systems are useful for different purposes. No single system captures every aspect of climate.

Climate Zones and Biomes Are Not the Same Thing

Climate and biome are closely related but are not interchangeable.

A climate zone describes physical climatic conditions such as temperature and precipitation.

A biome describes a large ecological community characterized by its vegetation and other organisms.

For example, climate helps determine whether a location supports tropical rainforest, desert, grassland, or tundra. However, soils, fire, disturbance, elevation, species interactions, and human land use also influence ecosystems.

Climate Variability

Climate variability refers to fluctuations in climate around its usual state on time scales ranging from months and years to decades and longer. However, climate is naturally variable. One decade may contain several unusually wet years, while another may contain prolonged drought.

Some variability develops internally through interactions among the atmosphere, oceans, land, ice, and biosphere.

Important examples include:

• El Niño-Southern Oscillation (ENSO): A coupled ocean-atmosphere pattern in the tropical Pacific that includes El Niño and La Niña.
• North Atlantic Oscillation (NAO): Variations in atmospheric pressure over the North Atlantic that influence weather in Europe, eastern North America, and surrounding regions.
• Indian Ocean Dipole (IOD): Changes in sea-surface temperature differences across the Indian Ocean that influence rainfall patterns.
• Pacific Decadal Oscillation (PDO): A pattern of North Pacific sea-surface temperature variability that occurs mainly over longer time scales than individual ENSO events.

Climate also varies in response to outside influences such as volcanic eruptions and changes in solar radiation.

Climate Anomalies

A climate anomaly is the difference between an observed value and a reference value.

For example:

Average July temperature = 25 °C
Observed July temperature = 27 °C

Temperature anomaly = 27 °C − 25 °C = +2 °C

Anomalies are useful because they make it easier to compare changes among locations with very different normal climates.

Microclimates

A microclimate is the climate of a small area that differs from the surrounding region.

Microclimates may occur over an area as small as the space beneath a plant canopy or as large as a neighborhood.

Examples include:

• A shaded forest floor that remains cooler and more humid than an open field
• A south-facing slope in the Northern Hemisphere that receives more sunlight than a north-facing slope
• A valley where cold air collects at night
• A garden protected from wind by a wall
• A coastal area cooled by sea breezes
• An irrigated field with greater humidity than surrounding dry land

Urban Microclimates

Cities often form distinctive microclimates.

Concrete, asphalt, buildings, reduced vegetation, waste heat, and changes in airflow can make urban areas warmer than their surroundings, especially at night. This phenomenon is called the urban heat island effect.

Buildings also create localized patterns of shade, wind, precipitation runoff, and heat storage.

Because weather stations can be only a short distance apart yet occupy different surroundings, careful climate studies account for station location and changes in the local environment.

Climate Change

Climate change is a persistent change in the statistical characteristics of climate over decades or longer.

It can involve changes in:

• Average temperature
• Precipitation patterns
• Snow and ice
• Sea level
• Ocean conditions
• Seasonal timing
• Frequency or intensity of some extremes
• Geographic climate zones

Earth’s climate has changed naturally throughout its history. Natural drivers include orbital variations, volcanic activity, continental movement, solar changes, and interactions within the climate system.

Modern climate change also includes human influences. Increased concentrations of carbon dioxide and other greenhouse gases from fossil fuel use, land-use changes, and other activities alter Earth’s energy balance and are the primary cause of the current long-term global warming trend.

Climate change does not mean natural climate variability stops. Short-term variability continues and can temporarily strengthen or oppose a long-term trend.

For example, an individual region may experience an unusually cold winter during a long-term warming trend.

Climate change is a large topic in its own right and includes causes, evidence, impacts, feedbacks, projections, mitigation, and adaptation.

How Scientists Measure Climate

Modern climate records combine many observing systems.

Weather Stations

Land-based stations measure temperature, precipitation, humidity, pressure, wind, sunshine, and other variables.

Long station records are especially valuable for identifying trends.

Scientists account for changes that could introduce artificial shifts into a record, such as:

• Moving a weather station
• Changing instruments
• Changing observation times
• Urban development
• Changes in measurement procedures

Ocean Observations

Ships, buoys, floats, tide gauges, and satellites measure ocean temperature, salinity, currents, waves, sea level, and other properties.

Because oceans store and transport enormous quantities of heat, ocean observations are essential for understanding climate.

Satellites

Satellites provide broad geographic coverage and measure variables including:

• Cloud cover
• Atmospheric temperature
• Sea-surface temperature
• Snow and ice
• Vegetation
• Water vapor
• Radiation
• Sea level

Satellite records are relatively recent compared with many surface records, but their near-global coverage makes them extremely valuable.

Weather Balloons

Radiosondes carried by weather balloons measure temperature, humidity, pressure, and wind through the atmosphere.

These measurements help scientists study changes above Earth’s surface.

Climate Models

A climate model is a mathematical representation of the climate system.

Models use physical laws and numerical calculations to simulate interactions among the atmosphere, oceans, land surface, ice, and other components of Earth.

How Climate Models Work

In many models, Earth is divided into three-dimensional grid cells.

Within and between these cells, computers calculate processes involving:

• Air movement
• Ocean circulation
• Heat transfer
• Solar and infrared radiation
• Water vapor
• Clouds and precipitation
• Sea ice
• Snow
• Soil moisture
• Carbon cycling

Processes that occur at scales smaller than the model grid may be represented using parameterizations, mathematical approximations based on observations and physical understanding.

Types of Climate Models

Climate models range in complexity.

Energy balance models:
Simplified models that focus mainly on energy entering and leaving the Earth system.

General circulation models (GCMs):
Three-dimensional models that simulate large-scale atmospheric or oceanic circulation.

Coupled atmosphere-ocean models:
Models in which the atmosphere and ocean interact dynamically.

Earth system models:
More comprehensive models that may include atmospheric chemistry, vegetation, carbon cycles, ice sheets, and biological processes.

Regional climate models:
Higher-resolution models used to investigate a particular geographic area.

Climate Projection vs Weather Forecast

Climate models generally do not attempt to predict the exact weather on a particular day decades from now.

Instead, they project how the statistical properties of climate may change under specified conditions.

A weather forecast might ask:

Will it rain in Chicago next Tuesday?

A climate projection might ask:

How could the frequency of heavy rainfall events in the Midwest change over coming decades?

The second question does not require knowing the exact sequence of individual storms.

Testing Climate Models

Scientists evaluate climate models by determining whether they can reproduce observed features of climate.

Models can be run using known past conditions and compared with historical observations. This process is sometimes called a hindcast.

Researchers also compare many model simulations rather than relying on a single run. These ensembles help separate robust patterns from effects caused by natural variability or uncertain assumptions.

Climate models are imperfect, but they are useful tools for testing hypotheses, understanding the climate system, and estimating possible future conditions.

Paleoclimatology

Paleoclimatology is the study of climates that existed before widespread instrumental weather records.

Direct thermometer measurements cover only a tiny fraction of Earth’s history. To investigate earlier climates, scientists use proxy records.

A climate proxy is a measurable characteristic that preserves information related to past environmental conditions.

Tree Rings

Many trees produce one growth ring each year.

Ring width, density, and chemical composition may reflect temperature, moisture, growing-season length, or other environmental conditions.

Tree rings provide especially detailed climate records because individual years can often be identified.

Ice Cores

Scientists drill long cores from glaciers and ice sheets.

Ice layers can preserve:

• Stable isotopes related to past temperature
• Dust
• Volcanic ash and sulfate
• Sea salts
• Pollen
• Bubbles containing samples of ancient atmosphere

Air trapped in ice provides direct evidence of past atmospheric composition.

Ocean and Lake Sediments

Sediments accumulate layer by layer and preserve minerals, pollen, microorganisms, organic material, and chemical signals.

Sediment cores can provide climate records extending hundreds of thousands or millions of years into the past.

Corals

Corals build growth layers that preserve information about ocean temperature, salinity, and other environmental conditions.

Cave Deposits

Stalagmites and other cave formations, collectively called speleothems, contain chemical and isotopic records influenced by temperature and rainfall.

Fossils and Pollen

The presence and distribution of organisms provide evidence about environmental conditions.

For example, pollen preserved in sediments reveals which plants lived in an area and therefore provides clues about past climate.

Why Paleoclimatology Matters

Paleoclimate records show how climate behaved before modern instruments existed.

They help scientists:

• Identify natural climate variability
• Study ice ages and warm periods
• Understand climate feedbacks
• Test climate models
• Investigate abrupt climate changes
• Compare modern changes with past conditions

Different proxies have different strengths, uncertainties, geographic coverage, and time resolution. Scientists therefore often combine multiple independent records.

Climate Exists on Different Spatial Scales

Climate can be studied at several scales.

Global climate: Conditions averaged or analyzed across the entire Earth.

Regional climate: Climate of a large geographic area, such as the Mediterranean or southeastern United States.

Local climate: Climate of a city, valley, coastline, or similar area.

Microclimate: Climate of a very small environment, such as a forest clearing, hillside, garden, street, or building site.

Processes operating at one scale can influence another. For example, global atmospheric circulation affects regional rainfall, while urban development modifies local climate.

Climate on Other Worlds

Earth is not the only world with a climate. Planetary climatology studies long-term atmospheric conditions and climate processes on planets, moons, and even planets orbiting other stars.

Comparing other worlds with Earth helps scientists understand which factors control climate. Venus has a dense carbon dioxide atmosphere and an extremely strong greenhouse effect, making its surface hotter than that of any other planet. Mars also has an atmosphere dominated by carbon dioxide, but its atmosphere is very thin, so the planet is cold and experiences large temperature variations. Titan, Saturn’s largest moon, has a thick nitrogen-rich atmosphere, seasons, clouds, and precipitation, but its weather cycle involves methane rather than liquid water.

Scientists also adapt Earth climate models to investigate the possible climates of exoplanets. By varying properties such as atmospheric composition, stellar radiation, rotation, oceans, and land area, researchers explore which planetary conditions could produce stable climates and potentially support liquid water.

Studying such dramatically different worlds provides another way to test our understanding of the physical processes that control Earth’s climate.

Common Misconceptions About Climate

Climate is just average weather.

Averages are important, but climate also includes seasonal cycles, variability, extremes, and the statistical distribution of weather conditions.

Climate means exactly 30 years of weather.

Thirty years is a standard period for calculating climate normals. It is not a universal minimum or maximum time scale for climate research.

Weather and climate are the same thing.

Weather describes short-term atmospheric conditions. Climate describes their long-term patterns.

A cold day disproves global warming.

A single day, storm, season, or local event does not determine a long-term global climate trend. Weather continues to vary as climate changes.

Tropical climates are always rainy.

All tropical climates are warm, but precipitation varies. Tropical rainforest climates remain wet throughout the year, while tropical savanna climates have pronounced wet and dry seasons.

Deserts are always hot.

A desert is defined primarily by aridity rather than high temperature. Cold deserts occur in Central Asia, Patagonia, Antarctica, and other regions.

Climate classifications are exact natural boundaries.

Climate changes gradually across most landscapes. Classification systems place useful boundaries on continuous variation.

Climate never changed before humans.

Earth’s climate has changed many times because of natural processes. The existence of natural climate change does not rule out human causes of modern climate change.

Climate models are simply weather forecasts far into the future.

Climate models primarily estimate statistical patterns and responses of the climate system rather than the exact sequence of future daily weather.

Frequently Asked Questions

What is climate in simple terms?

Climate is the long-term pattern of weather in a place. It describes typical conditions, seasons, variability, and extremes over many years.

What is the difference between weather and climate?

Weather is the short-term state of the atmosphere, while climate describes long-term patterns of weather.

How many years define climate?

Scientists commonly use 30-year periods to calculate standard climate normals. However, climate can be studied over shorter seasonal-to-decadal periods or across centuries and millions of years, depending on the question.

What are the main climate variables?

Important climate variables include temperature, precipitation, humidity, atmospheric pressure, wind, cloud cover, solar radiation, snow, ice, and evaporation.

What are the main factors that determine climate?

Major climate controls include latitude, elevation, distance from oceans, ocean currents, atmospheric circulation, topography, land cover, snow and ice, and atmospheric composition.

What are the five main climate types?

In the Köppen-Geiger system, the five major groups are tropical (A), dry (B), temperate (C), continental (D), and polar (E).

Is highland climate a Köppen climate group?

Not in the standard five-group Köppen-Geiger system. Some maps and educational systems add an H category for highland climates because mountain conditions are complex and vary strongly with elevation.

What is a climate normal?

A climate normal is a statistical measure, usually an average, calculated from climate observations over a standard 30-year period.

What is a climate anomaly?

A climate anomaly is the difference between an observed value and a reference average.

What is a microclimate?

A microclimate is the climate of a small area that differs from the surrounding region.

Does climate change naturally?

Yes. Climate changes naturally because of processes such as orbital variations, volcanic activity, solar variations, plate tectonics, and internal interactions within the climate system. Human activities can also cause climate change.

What is climate variability?

Climate variability refers to temporary or recurring fluctuations around typical climate conditions. El Niño and La Niña are important examples.

Can climate models predict the exact weather decades from now?

No. Their purpose is generally to simulate long-term climate statistics and responses rather than the exact weather on individual future days.

How do scientists know what ancient climates were like?

Scientists use climate proxies such as ice cores, tree rings, sediments, corals, fossils, pollen, and cave deposits.

Glossary

Climate: The long-term statistical pattern of weather conditions in a location, region, or the Earth as a whole.

Climate anomaly: The difference between an observed climate variable and its reference value.

Climate change: A persistent change in the statistical characteristics of climate over decades or longer.

Climate model: A mathematical representation used to simulate the climate system.

Climate normal: A statistical climate value calculated over a standard reference period, commonly 30 years.

Climate variability: Fluctuations in climate around its average or expected state.

Climatology: The scientific study of climate.

Climate proxy: Natural evidence used to infer past climatic conditions.

Forcing: An influence that changes Earth’s energy balance or otherwise drives a response in the climate system.

Microclimate: The climate of a small area that differs from surrounding conditions.

Paleoclimatology: The scientific study of past climates, particularly those before widespread instrumental records.

Weather: The short-term state of the atmosphere at a particular time and place.

References

• Beck, Hylke E.; Zimmermann, Niklaus E.; McVicar, Tim R.; Vergopolan, Noemi; Berg, Alexis; Wood, Eric F. (2018). “Present and future Köppen-Geiger climate classification maps at 1-km resolution”. Scientific Data. 5 180214. doi:10.1038/sdata.2018.214
• Joos, Fortunat; Spahni, Renato (2008). “Rates of change in natural and anthropogenic radiative forcing over the past 20,000 years”. Proceedings of the National Academy of Sciences. 105 (5): 1425–1430. doi:10.1073/pnas.0707386105
• Rohli, Robert. V.; Vega, Anthony J. (2018). Climatology (4th ed.). Jones & Bartlett Learning. ISBN 978-1284126563.
• Thornthwaite, C. W. (1948). “An Approach Toward a Rational Classification of Climate”. Geographical Review. 38 (1): 55–94. doi:10.2307/210739