Climatology (from
Greek , ''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, 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
Atmospheric science is the study of the Earth's atmosphere and its various inner-working physical processes. Meteorology includes atmospheric chemistry and atmospheric physics with a major focus on weather forecasting. Climatology is the study of ...
and a subfield of
physical geography, which is one of the
Earth science
Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres ...
s. Climatology now includes aspects of
oceanography
Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamic ...
and
biogeochemistry.
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,
mechanisms of climate changes and
modern 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 variability and change, Climate change in a broader sense also includes ...
. Basic knowledge of climate can be used within shorter term
weather forecasting, for instance about climatic cycles such as the
El Niño–Southern Oscillation (ENSO), the
Madden–Julian oscillation (MJO), the
North Atlantic oscillation
The North Atlantic Oscillation (NAO) is a weather phenomenon over the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High. Through fluctuations in the ...
(NAO), the
Arctic oscillation (AO), the
Pacific decadal oscillation (PDO), and the Interdecadal Pacific Oscillation (IPO).
Climate models 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 around 400
BCE. 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'', remained influential throughout history.
Chinese scientist
Shen Kuo
Shen Kuo (; 1031–1095) or Shen Gua, courtesy name Cunzhong (存中) and pseudonym Mengqi (now usually given as Mengxi) Weng (夢溪翁),Yao (2003), 544. was a Chinese polymathic scientist and statesman of the Song dynasty (960–1279). Shen wa ...
(1031–1095) inferred that climates naturally shifted over an enormous span of time, after observing
petrified bamboos found underground near Yanzhou (modern day
Yan'an,
Shaanxi province), a dry-climate area unsuitable for the growth of bamboo.
The invention of the
thermometer and the
barometer during the
Scientific Revolution allowed for systematic recordkeeping, that began as early as 1640–1642 in England.
Early climate researchers include
Edmund Halley, 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
The Gulf Stream, together with its northern extension the North Atlantic Current, North Atlantic Drift, is a warm and swift Atlantic Ocean, Atlantic ocean current that originates in the Gulf of Mexico and flows through the Straits of Florida a ...
for use in sending mail from the United States to Europe.
Francis Galton
Sir Francis Galton, FRS FRAI (; 16 February 1822 – 17 January 1911), was an English Victorian era polymath: a statistician, sociologist, psychologist, anthropologist, tropical explorer, geographer, inventor, meteorologist, proto- ...
(1822–1911) invented the term ''
anticyclone''.
Helmut Landsberg (1906–1985) fostered the use of
statistical analysis
Statistical inference is the process of using data analysis to infer properties of an underlying distribution of probability.Upton, G., Cook, I. (2008) ''Oxford Dictionary of Statistics'', OUP. . Inferential statistical analysis infers propertie ...
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'', or an average of weather and
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, 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 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 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 and
agriculture.
Paleoclimatology seeks to reconstruct and understand past climates by examining records such as
ice cores
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ic ...
and
tree rings
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
(
dendroclimatology).
Paleotempestology uses these same records to help determine hurricane frequency over millennia.
Historical climatology 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, regional climatology,
bioclimatology Bioclimatology is the interdisciplinary field of science that studies the interactions between the biosphere and the Earth's atmosphere on time scales of the order of seasons or longer (in contrast to biometeorology).
Examples of relevant processes ...
, and
synoptic climatology. The study of the
hydrological cycle
The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...
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
A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a measure.
Models c ...
, either
statistical
Statistics (from German: ''Statistik'', "description of a state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industria ...
or
mathematical, 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
In mathematics, a differential equation is an equation that relates one or more unknown functions and their derivatives. In applications, the functions generally represent physical quantities, the derivatives represent their rates of change, an ...
. These equations are coupled and nonlinear, so that approximate solutions are obtained by using numerical methods to create
global climate models. Climate is sometimes modeled as a
stochastic process
In probability theory and related fields, a stochastic () or random process is a mathematical object usually defined as a family of random variables. Stochastic processes are widely used as mathematical models of systems and phenomena that appea ...
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
thermometers, to
prehistoric
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of ...
ice extracted from
glaciers. As measuring technology changes over time, records of data cannot be compared directly. As cities are generally warmer than the surrounding areas,
urbanization has made it necessary to constantly correct data for this
urban heat island 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 gas
A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
es such as
carbon dioxide. 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
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
global climate models 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:
climate variability, 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
oceans. Oceans act as a moderating factor, so that land close to it has typically has mild
winters and moderate summers. The atmosphere interacts with other spheres of the
climate system, with winds generating
ocean currents 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. How climates are classified depends on what the application is. A
wind energy 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, was developed in the late nineteenth century and is based on vegetation. It uses monthly temperature and
precipitation 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.
El Niño–Southern Oscillation (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
The North Atlantic Oscillation (NAO) is a weather phenomenon over the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High. Through fluctuations in the ...
is a mode of variability that is mainly contained to the lower atmosphere, the
troposphere. The layer of atmosphere above, the
stratosphere
The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...
is also capable of creating its own variability, most importantly in the
Madden–Julian oscillation (MJO), which has a cycle of approximately 30 to 60 days. The
Interdecadal Pacific oscillation
The Interdecadal Pacific oscillation (IPO) is an oceanographic/meteorological phenomenon similar to the Pacific decadal oscillation
The Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability c ...
can create changes in the Pacific Ocean and lower atmosphere on decadal time scales.
Climate change
Climate change occurs when changes in Earth's
climate system result in new
weather 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. The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines
Earth's energy budget. 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.
Modern 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 variability and change, Climate change in a broader sense also includes ...
is driven by the human emissions of
greenhouse gas
A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
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
precipitation,
storm tracks and cloudiness. Warmer temperatures are driving further changes in the
climate system, such as the
widespread melt of glaciers,
sea level rise and shifts in flora and fauna.
Differences with meteorology
In contrast to
meteorology, which focuses on short term
weather 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
Climatology (from Greek , ''klima'', "place, zone"; and , ''-logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. This modern field of study ...
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
A prediction (Latin ''præ-'', "before," and ''dicere'', "to say"), or forecast, is a statement about a future event or data. They are often, but not always, based upon experience or knowledge. There is no universal agreement about the exact ...
future
climate change.
Phenomena of climatological interest include the
atmospheric boundary layer
In meteorology, the planetary boundary layer (PBL), also known as the atmospheric boundary layer (ABL) or peplosphere, is the lowest part of the atmosphere and its behaviour is directly influenced by its contact with a planetary surface. On Ear ...
,
circulation patterns,
heat transfer (
radiative,
convective
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convect ...
and
latent), interactions between the atmosphere and the oceans and land surface (particularly vegetation,
land use and
topography), 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
teleconnection
Teleconnection in atmospheric science refers to climate anomalies being related to each other at large distances (typically thousands of kilometers). The most emblematic teleconnection is that linking sea-level pressure at Tahiti and Darwin, Austr ...
s, 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.
See also
*
Biogeochemistry
*
Climate as complex networks
The field of complex networks has emerged as an important area of science to generate novel insights into nature of complex systems The application of network theory to climate science is a young and emerging field. To identify and analyze patterns ...
*
Climatic geomorphology
*
Climate reanalysis
An atmospheric reanalysis (also: meteorological reanalysis and climate reanalysis) is a meteorological and climate data assimilation project which aims to assimilate historical atmospheric observational data spanning an extended period, using a si ...
*
Geophysics
*
Tropical cyclone rainfall climatology
A tropical cyclone rainfall climatology is developed to determine rainfall characteristics of past tropical cyclones. A tropical cyclone rainfall climatology can be used to help forecast current or upcoming tropical cyclone impacts. The degree o ...
*
Urban climatology
Urban climatology is the study of urban climate. It is a branch of climatology that concerns interactions between urban areas and the atmosphere, the effects they have on one another, and the varying spatial and temporal scales at which these proc ...
*
List of climate scientists
This list of climate scientists contains famous or otherwise notable persons who have contributed to the study of climate science. The list is compiled manually, so will not be complete, up to date, or comprehensive. See also :Climatologists.
...
*
List of women climate scientists and activists
The following is a list of women climate scientists and activists by nationality – women who are well known for their work in the field of climatology.
Introduction
Women have made major contributions to climate change research and policy an ...
References
Books
*
*
*
*
Further reading
*
Jenny Uglow
Jennifer Sheila Uglow (, (accessed 5 February 2008).
(accessed 19 August 2022). born 1947) is an English biographer, hi ...
, "What the Weather Is" (review of Sarah Dry, ''Waters of the World: The Story of the Scientists Who Unraveled the Mysteries of Our Oceans, Atmosphere, and Ice Sheets and Made the Planet Whole'', University of Chicago Press, 2019, 332 pp.), ''
The New York Review of Books'', vol. LXVI, no. 20 (19 December 2019), pp. 56–58.
External links
Climate Science Special Report– U.S. Global Change Research Program
KNMI Climate ExplorerThe 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