Köppen-Geiger climate classification (1980-2016)

Climatology (from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

, ''klima'', "place, zone"; and , ''

-logia ''-logy'' is a suffix in the English language, used with words originally adapted from Ancient Greek ending in ('). The earliest English examples were anglicizations of the French '' -logie'', which was in turn inherited from the Latin '' -logi ...

'') or climate science is the scientific study of Earth's

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

, typically defined as weather conditions averaged over a period of at least 30 years. This modern field of study is regarded as a branch of the atmospheric sciences and a subfield of

physical geography Physical geography (also known as physiography) is one of the three main branches of geography. Physical geography is the branch of natural science which deals with the processes and patterns in the natural environment such as the atmosphere, ...

, which is one of the Earth sciences. Climatology now includes aspects of oceanography and

biogeochemistry Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the cryosphere, ...

. The main methods employed by climatologists are the analysis of observations and modelling of the physical processes that determine the climate. The main topics of research are the study of

climate variability Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more ...

, mechanisms of climate changes and modern climate change. Basic knowledge of climate can be used within shorter term weather forecasting, for instance about climatic cycles such as the

El Niño–Southern Oscillation El Niño–Southern Oscillation (ENSO) is an irregular periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. The warming phase of the sea te ...

(ENSO), the

Madden–Julian oscillation The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal (30- to 90-day) variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric ...

(MJO), the North Atlantic oscillation (NAO), the

Arctic oscillation The Arctic oscillation (AO) or Northern Annular Mode/Northern Hemisphere Annular Mode (NAM) is a weather phenomenon at the Arctic pole north of 20 degrees latitude. It is an important mode of climate variability for the Northern Hemisphere. The s ...

(AO), the

Pacific decadal oscillation The Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. O ...

(PDO), and the Interdecadal Pacific Oscillation (IPO).

Climate models Numerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the c ...

are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate. Weather is known as the condition of the atmosphere over a period of time, while climate has to do with the atmospheric condition over an extended to indefinite period of time.

History

The Greeks began the formal study of climate; in fact the word climate is derived from the Greek word klima, meaning "slope," referring to the slope or inclination of the Earth's axis. Arguably the most influential classic text on climate was ''On Airs, Water and Places'' written by

Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history o ...

around 400

BCE Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the or ...

. This work commented on the effect of climate on human health and cultural differences between Asia and Europe. This idea that climate controls which countries excel depending on their climate, or ''

climatic determinism Environmental determinism (also known as climatic determinism or geographical determinism) is the study of how the physical environment predisposes societies and states towards particular development trajectories. Jared Diamond, Jeffrey Herbst, ...

'', remained influential throughout history. Chinese scientist Shen Kuo (1031–1095) inferred that climates naturally shifted over an enormous span of time, after observing petrified

bamboo Bamboos are a diverse group of evergreen perennial flowering plants making up the subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family. The origin of the word "bamboo" is uncertain, ...

s found underground near Yanzhou (modern day Yan'an,

Shaanxi Shaanxi (alternatively Shensi, see § Name) is a landlocked province of China. Officially part of Northwest China, it borders the province-level divisions of Shanxi (NE, E), Henan (E), Hubei (SE), Chongqing (S), Sichuan (SW), Gansu (W), N ...

province), a dry-climate area unsuitable for the growth of bamboo. The invention of the

thermometer A thermometer is a device that measures temperature or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer ...

and the

barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

during the

Scientific Revolution The Scientific Revolution was a series of events that marked the emergence of modern science during the early modern period, when developments in mathematics, physics, astronomy, biology (including human anatomy) and chemistry transfo ...

allowed for systematic recordkeeping, that began as early as 1640–1642 in England. Early climate researchers include

Edmund Halley Edmond (or Edmund) Halley (; – ) was an English astronomer, mathematician and physicist. He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720. From an observatory he constructed on Saint Helena in 1676–77, Hal ...

, who published a map of the trade winds in 1686 after a voyage to the southern hemisphere. Benjamin Franklin (1706–1790) first mapped the course of the Gulf Stream for use in sending mail from the United States to Europe. Francis Galton (1822–1911) invented the term ''

anticyclone An anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere as viewed from ...

''.

Helmut Landsberg Helmut Erich Landsberg (1906–1985) was a noted and influential climatologist. He was born in Frankfurt, Germany, February 9, 1906 and died December 6, 1985 in Geneva, Switzerland while attending a meeting of the World Meteorological Orga ...

(1906–1985) fostered the use of statistical analysis in climatology, which led to its evolution into a physical science. In the early 20th century, climatology was mostly focused on the description of regional climates. This descriptive climatology was mainly an applied science, giving farmers and other interested people statistics about what the normal weather was and how big chances were of extreme events. To do this, climatologists had to define a ''

climate normal Climatological normal or climate normal (CN) is a 30-year average of a weather variable for a given time of year.weather extremes over a period of typically 30 years. Around the middle of the 20th century, many assumptions in meteorology and climatology considered climate to be roughly constant. While scientists knew of past climate change such as the

ice ages An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...

, the concept of climate as unchanging was useful in the development of a general theory of what determines climate. This started to change in the decades that followed, and while the

history of climate change science The history of the scientific discovery of climate change began in the early 19th century when ice ages and other natural changes in paleoclimate were first suspected and the natural greenhouse effect was first identified. In the late 19th centu ...

started earlier, climate change only became one of the mean topics of study for climatologists in the seventies and onward.

Subfields

Various subfields of climatology study different aspects of the climate. There are different categorizations of the fields in climatology. The

American Meteorological Society The American Meteorological Society (AMS) is the premier scientific and professional organization in the United States promoting and disseminating information about the atmospheric, oceanic, and hydrologic sciences. Its mission is to advance th ...

for instance identifies descriptive climatology, scientific climatology and applied climatology as the three subcategories of climatology, a categorization based on the complexity and the purpose of the research. Applied climatologists apply their expertise to different industries such as

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to ...

and

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...

. Paleoclimatology seeks to reconstruct and understand past climates by examining records such as ice cores and tree rings (

dendroclimatology Dendroclimatology is the science of determining past climates from trees (primarily properties of the annual tree rings). Tree rings are wider when conditions favor growth, narrower when times are difficult. Other properties of the annual rings, s ...

Paleotempestology Paleotempestology is the study of past tropical cyclone activity by means of geological proxies as well as historical documentary records. The term was coined by American meteorologist Kerry Emanuel. The usual approach in paleotempestology is ...

uses these same records to help determine hurricane frequency over millennia.

Historical climatology Historical climatology is the study of historical changes in climate and their effect on civilization from the emergence of homininis to the present day. This differs from paleoclimatology which encompasses climate change over the entire history o ...

is the study of climate as related to human history and thus focuses only on the last few thousand years. Boundary-layer climatology is preoccupied with exchanges in water, energy and momentum near the surface. Further identified subfields are physical climatology, dynamic climatology,

tornado climatology Tornadoes have been recorded on all continents except Antarctica. They are most common in the middle latitudes where conditions are often favorable for convective storm development. The United States has the most tornadoes of any country, as we ...

, regional climatology, bioclimatology, and synoptic climatology. The study of the hydrological cycle over long time scales is sometimes called hydroclimatology, in particular when studying the effects of climate change on the water cycle.

Methods

The study of contemporary climates incorporates meteorological data accumulated over many years, such as records of rainfall, temperature and atmospheric composition. Knowledge of the atmosphere and its dynamics is also embodied in models, either statistical or

mathematical Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...

, which help by integrating different observations and testing how they fit together. Modeling is used for understanding past, present and potential future climates. Climate research is made difficult by the large scale, long time periods, and complex processes which govern climate. Climate is governed by physical laws which can be expressed as differential equations. These equations are coupled and nonlinear, so that approximate solutions are obtained by using numerical methods to create

global climate model A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic terms ...

s. Climate is sometimes modeled as a stochastic process but this is generally accepted as an approximation to processes that are otherwise too complicated to analyze.

Climate data

The collection of long record of climate variables is essential for the study of climate. Climatology deals with the aggregate data that meteorology has collected. Scientists use both direct and indirect observations of the climate, from Earth observing satellites and scientific instrumentation such as a global network of

s, to prehistoric ice extracted from

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...

s. As measuring technology changes over time, records of data cannot be compared directly. As cities are generally warmer than the surrounding areas,

urbanization Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly t ...

has made it necessary to constantly correct data for this

urban heat island An urban heat island (UHI) is an urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparen ...

effect.

Models

Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the weather and climate system to projections of future climate. All climate models balance, or very nearly balance, incoming energy as short wave (including visible) electromagnetic radiation to the earth with outgoing energy as long wave (infrared) electromagnetic radiation from the earth. Any unbalance results in a change in the average temperature of the earth. Most climate models include the radiative effects of greenhouse gases such as

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

. These models predict an upward trend in the surface temperatures, as well as a more rapid increase in temperature at higher latitudes. Models can range from relatively simple to complex: * A simple radiant heat transfer model that treats the earth as a single point and averages outgoing energy * this can be expanded vertically (radiative-convective models), or horizontally * Coupled atmosphere–ocean– sea ice

global climate models A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamics, therm ...

discretise and solve the full equations for mass and energy transfer and radiant exchange. * Earth system models further include the biosphere. Additionally, they are available on different resolutions ranging from >100 km to 1 km. High resolutions in global climate models are computational very demanding and only few global datasets exists. Examples are ICON or mechnistically downscaled data such as CHELSA (Climatologies at high resolution for the earth's land surface areas).

Topics of research

Topics that climatologists study fall roughly into three categories:

, mechanisms of climatic change change and modern climate change.

Climatological processes

Various factors impact the average state of the atmosphere at a particular location. For instance, midlatitudes will have a pronounced seasonal cycle in temperature whereas tropical regions show little variation in temperature over the year. Another major control in climate is continentality: the distance to major water bodies such as

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

s. Oceans act as a moderating factor, so that land close to it has typically has mild

winter Winter is the coldest season of the year in polar and temperate climates. It occurs after autumn and before spring. The tilt of Earth's axis causes seasons; winter occurs when a hemisphere is oriented away from the Sun. Different cultur ...

s and moderate summers. The atmosphere interacts with other spheres of the

climate system Earth's climate system is a complex system having five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). '' ...

, with winds generating

ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours ...

s that transport heat around the globe.

Climate classification

Classification is an important aspect of many sciences as a tool of simplifying complicated processes. Different climate classifications have been developed over the centuries, with the first ones in

Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean Sea, Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, classical antiquity ( AD 600), th ...

. How climates are classified depends on what the application is. A

wind energy Wind power or wind energy is mostly the use of wind turbines to generate electricity. Wind power is a popular, sustainable, renewable energy source that has a much smaller impact on the environment than burning fossil fuels. Historically, w ...

producer will require different information (wind) in the classification than somebody interested in agriculture, for who precipitation and temperature are more important. The most widely used classification, the

Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notabl ...

, was developed in the late nineteenth century and is based on vegetation. It uses monthly temperature and

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

data.

Climate variability

There are different modes of variability: recurring patterns of temperature or other climate variables. They are quantified with different indices. Much in the way the Dow Jones Industrial Average, which is based on the stock prices of 30 companies, is used to represent the fluctuations in the stock market as a whole, climate indices are used to represent the essential elements of climate. Climate indices are generally devised with the twin objectives of simplicity and completeness, and each index typically represents the status and timing of the climate factor it represents. By their very nature, indices are simple, and combine many details into a generalized, overall description of the atmosphere or ocean which can be used to characterize the factors which impact the global climate system.

(ENSO) is a coupled ocean-atmosphere phenomenon in the Pacific Ocean responsible for most of the global variability in temperature, and has a cycle between two and seven years. The North Atlantic oscillation is a mode of variability that is mainly contained to the lower atmosphere, the

troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...

. The layer of atmosphere above, the stratosphere is also capable of creating its own variability, most importantly in the

(MJO), which has a cycle of approximately 30 to 60 days. The Interdecadal Pacific oscillation can create changes in the Pacific Ocean and lower atmosphere on decadal time scales.

Climate change

Climate change occurs when changes in Earth's

result in new

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmos ...

patterns that remain in place for an extended period of time. This length of time can be as short as a few decades to as long as millions of years. The climate system receives nearly all of its energy from the sun. The climate system also gives off energy to

outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...

. The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines

Earth's energy budget Earth's energy budget accounts for the balance between the energy that Earth receives from the Sun and the energy the Earth loses back into outer space. Smaller energy sources, such as Earth's internal heat, are taken into consideration, but m ...

. When the incoming energy is greater than the outgoing energy, earth's energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and earth experiences cooling. Climate change also influences the average

sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardise ...

. Modern climate change is driven by the human emissions of greenhouse gas from the burning of fossil fuel driving up global mean surface temperatures. Rising temperatures are only one aspect of modern climate change though, with includes observed changes in

storm track ''Storm Track'' was the first magazine for and about storm chasing. The magazine was in circulation between 1977 and 2002. History and profile ''Storm Track'' was started in 1977 by chasing pioneer David Hoadley following an informal meeting o ...

s and cloudiness. Warmer temperatures are driving further changes in the

, such as the widespread melt of glaciers,

sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...

and shifts in flora and fauna.

Differences with meteorology

In contrast to

meteorology Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did no ...

, which focuses on short term

systems lasting up to a few weeks, climatology studies the frequency and trends of those systems. It studies the periodicity of weather events over years to millennia, as well as changes in long-term average weather patterns, in relation to atmospheric conditions. Climatologists study both the nature of climates – local, regional or global – and the natural or human-induced factors that cause climates to change. Climatology considers the past and can help predict future

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

. Phenomena of climatological interest include the atmospheric boundary layer, circulation patterns,

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

( radiative, convective and

latent Latency or latent may refer to: Science and technology * Latent heat, energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process * Latent variable, a variable that is not directly observed but inferred ...

), interactions between the atmosphere and the oceans and land surface (particularly vegetation,

land use Land use involves the management and modification of natural environment or wilderness into built environment such as settlements and semi-natural habitats such as arable fields, pastures, and managed woods. Land use by humans has a long ...

and

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sc ...

), and the chemical and physical composition of the atmosphere.

Use in weather forecasting

A more complicated way of making a forecast, the analog technique requires remembering a previous weather event which is expected to be mimicked by an upcoming event. What makes it a difficult technique to use is that there is rarely a perfect analog for an event in the future. Some call this type of forecasting pattern recognition, which remains a useful method of observing rainfall over data voids such as oceans with knowledge of how satellite imagery relates to precipitation rates over land, as well as the forecasting of precipitation amounts and distribution in the future. A variation on this theme is used in medium range forecasting, which is known as teleconnections, when systems in other locations are used to help pin down the location of a system within the surrounding regime. One method of using teleconnections are by using climate indices such as ENSO-related phenomena.Thinkquest.org
Teleconnections: Linking El Niño with Other Places.
Retrieved on 16 February 2007.

References

Books

* * * *

External links

Climate Science Special Report
– U.S. Global Change Research Program
KNMI Climate Explorer
The Royal Netherlands Meteorological Institute's Climate Explorer graphs climatological relationships of spatial and temporal data.

Amer. Inst. of Physics account of the history of the discipline of climatology in the 20th century {{Authority control Atmospheric sciences Climate and weather statistics Natural environment