
A general circulation model (GCM) is a type of
climate model
Numerical climate models (or climate system models) are mathematical models that can simulate the interactions of important drivers of climate. These drivers are the atmosphere, oceans, land surface and ice. Scientists use climate models to st ...
. It employs a
mathematical model
A mathematical model is an abstract and concrete, abstract description of a concrete system using mathematics, mathematical concepts and language of mathematics, language. The process of developing a mathematical model is termed ''mathematical m ...
of the general circulation of a planetary
atmosphere
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
or ocean. It uses the
Navier–Stokes equations
The Navier–Stokes equations ( ) are partial differential equations which describe the motion of viscous fluid substances. They were named after French engineer and physicist Claude-Louis Navier and the Irish physicist and mathematician Georg ...
on a rotating sphere with
thermodynamic
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of th ...
terms for various energy sources (
radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:
* ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...
,
latent heat
Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process—usually a first-order phase transition, like melting or condensation. ...
). These equations are the basis for computer programs used to
simulate the Earth's atmosphere or oceans. Atmospheric and oceanic GCMs (AGCM and
OGCM) are key components along with
sea ice
Sea ice arises as seawater freezes. Because ice is less density, dense than water, it floats on the ocean's surface (as does fresh water ice). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world' ...
and
land-surface components.
GCMs and global climate models are used for
weather forecasting
Weather forecasting or weather prediction is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather info ...
, understanding the
climate
Climate is the long-term weather pattern in a region, 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 meteoro ...
, and forecasting
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
.
Atmospheric GCMs (AGCMs) model the atmosphere and impose
sea surface temperature
Sea surface temperature (or ocean surface temperature) is the ocean temperature, temperature of ocean water close to the surface. The exact meaning of ''surface'' varies in the literature and in practice. It is usually between and below the sea ...
s as boundary conditions. Coupled atmosphere-ocean GCMs (AOGCMs, e.g.
HadCM3,
EdGCM,
GFDL CM2.X, ARPEGE-Climat) combine the two models. The first general circulation climate model that combined both oceanic and atmospheric processes was developed in the late 1960s at the
NOAA
The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...
Geophysical Fluid Dynamics Laboratory AOGCMs represent the pinnacle of complexity in climate models and internalise as many processes as possible. However, they are still under development and uncertainties remain. They may be coupled to models of other processes, such as the
carbon cycle
The carbon cycle is a part of the biogeochemical cycle where carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycl ...
, so as to better model feedback effects. Such integrated multi-system models are sometimes referred to as either "earth system models" or "global climate models."
Versions designed for decade to century time scale climate applications were created by
Syukuro Manabe and
Kirk Bryan at the
Geophysical Fluid Dynamics Laboratory (GFDL) in
Princeton, New Jersey
The Municipality of Princeton is a Borough (New Jersey), borough in Mercer County, New Jersey, United States. It was established on January 1, 2013, through the consolidation of the Borough of Princeton, New Jersey, Borough of Princeton and Pri ...
.
These models are based on the integration of a variety of fluid dynamical, chemical and sometimes biological equations.
Terminology
The acronym ''GCM'' originally stood for ''General Circulation Model''. Recently, a second meaning came into use, namely ''Global Climate Model''. While these do not refer to the same thing, General Circulation Models are typically the tools used for
modeling climate, and hence the two terms are sometimes used interchangeably. However, the term "global climate model" is ambiguous and may refer to an integrated framework that incorporates multiple components including a general circulation model, or may refer to the general class of climate models that use a variety of means to represent the climate mathematically.
Atmospheric and oceanic models
Atmospheric (AGCMs) and oceanic GCMs (OGCMs) can be coupled to form an atmosphere-ocean coupled general circulation model (CGCM or AOGCM). With the addition of submodels such as a sea ice model or a model for
evapotranspiration
Evapotranspiration (ET) refers to the combined processes which move water from the Earth's surface (open water and ice surfaces, bare soil and vegetation) into the Atmosphere of Earth, atmosphere. It covers both water evaporation (movement of w ...
over land, AOGCMs become the basis for a full climate model.
Structure
General Circulation Models (GCMs) discretise the equations for fluid motion and energy transfer and integrate these over time. Unlike simpler models, GCMs divide the atmosphere and/or oceans into grids of discrete "cells", which represent computational units. Unlike simpler models which make mixing assumptions, processes internal to a cell—such as convection—that occur on scales too small to be resolved directly are parameterised at the cell level, while other functions govern the interface between cells.
Three-dimensional (more properly four-dimensional) GCMs apply discrete equations for fluid motion and integrate these forward in time. They contain parameterisations for processes such as
convection
Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...
that occur on scales too small to be resolved directly.
A simple general circulation model (SGCM) consists of a dynamic core that relates properties such as temperature to others such as pressure and velocity. Examples are programs that solve the
primitive equations
The primitive equations are a set of nonlinear partial differential equations that are used to approximate global atmosphere, atmospheric flow and are used in most Global climate model, atmospheric models. They consist of three main sets of balance ...
, given energy input and energy
dissipation
In thermodynamics, dissipation is the result of an irreversible process that affects a thermodynamic system. In a dissipative process, energy ( internal, bulk flow kinetic, or system potential) transforms from an initial form to a final form, wh ...
in the form of scale-dependent
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...
, so that
atmospheric waves with the highest
wavenumber
In the physical sciences, the wavenumber (or wave number), also known as repetency, is the spatial frequency of a wave. Ordinary wavenumber is defined as the number of wave cycles divided by length; it is a physical quantity with dimension of ...
s are most attenuated. Such models may be used to study atmospheric processes, but are not suitable for climate projections.
Atmospheric GCMs (AGCMs) model the atmosphere (and typically contain a land-surface model as well) using imposed
sea surface temperature
Sea surface temperature (or ocean surface temperature) is the ocean temperature, temperature of ocean water close to the surface. The exact meaning of ''surface'' varies in the literature and in practice. It is usually between and below the sea ...
s (SSTs). They may include atmospheric chemistry.
AGCMs consist of a dynamical core that integrates the equations of fluid motion, typically for:
* surface pressure
* horizontal components of velocity in layers
* temperature and water vapor in layers
* radiation, split into solar/short wave and terrestrial/
infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
/long wave
*
parameters for:
** convection
** land surface processes
**
albedo
Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...
**
hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...
**
cloud cover
Cloud cover (also known as cloudiness, cloudage, or cloud amount) refers to the fraction of the sky obscured by clouds on average when observed from a particular location. Okta is the usual unit for measurement of the cloud cover. The cloud c ...
A GCM contains
prognostic equations that are a function of time (typically winds, temperature, moisture, and surface pressure) together with
diagnostic equations that are evaluated from them for a specific time period. As an example, pressure at any height can be diagnosed by applying the
hydrostatic equation to the predicted surface pressure and the predicted values of temperature between the surface and the height of interest. Pressure is used to compute the pressure gradient force in the time-dependent equation for the winds.
OGCMs model the ocean (with fluxes from the atmosphere imposed) and may contain a
sea ice
Sea ice arises as seawater freezes. Because ice is less density, dense than water, it floats on the ocean's surface (as does fresh water ice). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world' ...
model. For example, the standard resolution of
HadOM3 is 1.25 degrees in latitude and longitude, with 20 vertical levels, leading to approximately 1,500,000 variables.
AOGCMs (e.g.
HadCM3,
GFDL CM2.X) combine the two submodels. They remove the need to specify fluxes across the interface of the ocean surface. These models are the basis for model predictions of future climate, such as are discussed by the
IPCC
The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to "provide governments at all levels with scientific information that they can use to develop climate policies". The World M ...
. AOGCMs internalise as many processes as possible. They have been used to provide predictions at a regional scale. While the simpler models are generally susceptible to analysis and their results are easier to understand, AOGCMs may be nearly as hard to analyse as the climate itself.
Grid
The fluid equations for AGCMs are made discrete using either the
finite difference method
In numerical analysis, finite-difference methods (FDM) are a class of numerical techniques for solving differential equations by approximating Derivative, derivatives with Finite difference approximation, finite differences. Both the spatial doma ...
or the
spectral method
Spectral methods are a class of techniques used in applied mathematics and scientific computing to numerically solve certain differential equations. The idea is to write the solution of the differential equation as a sum of certain " basis funct ...
. For finite differences, a grid is imposed on the atmosphere. The simplest grid uses constant angular grid spacing (i.e., a latitude/longitude grid). However, non-rectangular grids (e.g., icosahedral) and grids of variable resolution
[
PDF create date 2004-10-28. See also ] are more often used. The LMDz model can be arranged to give high resolution over any given section of the planet.
HadGEM1 (and other ocean models) use an ocean grid with higher resolution in the tropics to help resolve processes believed to be important for the
El Niño Southern Oscillation (ENSO). Spectral models generally use a
Gaussian grid, because of the mathematics of transformation between spectral and grid-point space. Typical AGCM resolutions are between 1 and 5 degrees in latitude or longitude: HadCM3, for example, uses 3.75 in longitude and 2.5 degrees in latitude, giving a grid of 96 by 73 points (96 x 72 for some variables); and has 19 vertical levels. This results in approximately 500,000 "basic" variables, since each grid point has four variables (
''u'',''v'',
''T'',
''Q''), though a full count would give more (clouds; soil levels). HadGEM1 uses a grid of 1.875 degrees in longitude and 1.25 in latitude in the atmosphere; HiGEM, a high-resolution variant, uses 1.25 x 0.83 degrees respectively. These resolutions are lower than is typically used for weather forecasting. Ocean resolutions tend to be higher, for example, HadCM3 has 6 ocean grid points per atmospheric grid point in the horizontal.
For a standard finite difference model, uniform gridlines converge towards the poles. This would lead to computational instabilities (see
CFL condition) and so the model variables must be filtered along lines of latitude close to the poles. Ocean models suffer from this problem too, unless a rotated grid is used in which the North Pole is shifted onto a nearby landmass. Spectral models do not suffer from this problem. Some experiments use
geodesic grids and icosahedral grids, which (being more uniform) do not have pole-problems. Another approach to solving the grid spacing problem is to deform a
Cartesian cube
A cube or regular hexahedron is a three-dimensional space, three-dimensional solid object in geometry, which is bounded by six congruent square (geometry), square faces, a type of polyhedron. It has twelve congruent edges and eight vertices. It i ...
such that it covers the surface of a sphere.
Flux buffering
Some early versions of AOGCMs required an ''ad hoc'' process of "
flux correction" to achieve a stable climate. This resulted from separately prepared ocean and atmospheric models that each used an implicit flux from the other component different than that component could produce. Such a model failed to match observations. However, if the fluxes were 'corrected', the factors that led to these unrealistic fluxes might be unrecognised, which could affect model sensitivity. As a result, the vast majority of models used in the current round of IPCC reports do not use them. The model improvements that now make flux corrections unnecessary include improved ocean physics, improved resolution in both atmosphere and ocean, and more physically consistent coupling between the atmosphere and ocean submodels. Improved models now maintain stable, multi-century simulations of surface climate that are considered to be of sufficient quality to allow their use for climate projections.
Convection
Moist convection releases latent heat and is important to the Earth's energy budget. Convection occurs on too small a scale to be resolved by climate models, and hence it must be handled via parameters. This has been done since the 1950s. Akio Arakawa did much of the early work, and variants of his scheme are still used, although a variety of different schemes are now in use. Clouds are also typically handled with a parameter, for a similar lack of scale. Limited understanding of clouds has limited the success of this strategy, but not due to some inherent shortcomings of the method.
Software
Most models include software to diagnose a wide range of variables for comparison with observations or
study of atmospheric processes. An example is the 2-metre temperature, which is the standard height for near-surface observations of air temperature. This temperature is not directly predicted from the model but is deduced from surface and lowest-model-layer temperatures. Other software is used for creating plots and animations.
Projections
Coupled AOGCMs use
transient climate simulations to project/predict climate changes under various scenarios. These can be idealised scenarios (most commonly, CO
2 emissions increasing at 1%/yr) or based on recent history (usually the "IS92a" or more recently the
SRES scenarios). Which scenarios are most realistic remains uncertain.
The 2001
IPCC Third Assessment Reportbr>
Figure 9.3shows the global mean response of 19 different coupled models to an idealised experiment in which emissions increased at 1% per year
shows the response of a smaller number of models to more recent trends. For the 7 climate models shown there, the temperature change to 2100 varies from 2 to 4.5 °C with a median of about 3 °C.
Future scenarios do not include unknown events for example, volcanic eruptions or changes in solar forcing. These effects are believed to be small in comparison to
greenhouse gas
Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...
(GHG) forcing in the long term, but large volcanic eruptions, for example, can exert a substantial temporary cooling effect.
Human GHG emissions are a model input, although it is possible to include an economic/technological submodel to provide these as well. Atmospheric GHG levels are usually supplied as an input, though it is possible to include a carbon cycle model that reflects vegetation and oceanic processes to calculate such levels.
Emissions scenarios
For the six SRES marker scenarios, IPCC (2007:7–8) gave a "best estimate" of global mean temperature increase (2090–2099 relative to the period 1980–1999) of 1.8 °C to 4.0 °C.
Over the same time period, the "likely" range (greater than 66% probability, based on expert judgement) for these scenarios was for a global mean temperature increase of 1.1 to 6.4 °C.
[, in ]
In 2008 a study made climate projections using several emission scenarios. In a scenario where global emissions start to decrease by 2010 and then decline at a sustained rate of 3% per year, the likely global average temperature increase was predicted to be 1.7 °C above pre-industrial levels by 2050, rising to around 2 °C by 2100. In a projection designed to simulate a future where no efforts are made to reduce global emissions, the likely rise in global average temperature was predicted to be 5.5 °C by 2100. A rise as high as 7 °C was thought possible, although less likely.
Another no-reduction scenario resulted in a median warming over land (2090–99 relative to the period 1980–99) of 5.1 °C. Under the same emissions scenario but with a different model, the predicted median warming was 4.1 °C.
Model accuracy

AOGCMs internalise as many processes as are sufficiently understood. However, they are still under development and significant uncertainties remain. They may be coupled to models of other processes in
Earth system model
Earth system science (ESS) is the application of systems science to the Earth. In particular, it considers interactions and 'feedbacks', through material and energy fluxes, between the Earth's sub-systems' cycles, processes and "spheres"—atmosp ...
s, such as the
carbon cycle
The carbon cycle is a part of the biogeochemical cycle where carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycl ...
, so as to better model feedback. Most recent simulations show "plausible" agreement with the measured temperature anomalies over the past 150 years, when driven by observed changes in greenhouse gases and aerosols. Agreement improves by including both natural and anthropogenic forcings.
[IPCC]
Summary for Policy Makers
, in (pb: ).
Imperfect models may nevertheless produce useful results. GCMs are capable of reproducing the general features of the observed global temperature over the past century.
A debate over how to reconcile climate model predictions that upper air (tropospheric) warming should be greater than observed surface warming, some of which appeared to show otherwise, was resolved in favour of the models, following data revisions.
Cloud
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...
effects are a significant area of uncertainty in climate models. Clouds have competing effects on climate. They cool the surface by reflecting sunlight into space; they warm it by increasing the amount of infrared radiation transmitted from the atmosphere to the surface. In the 2001 IPCC report possible changes in cloud cover were highlighted as a major uncertainty in predicting climate.
Climate researchers around the world use climate models to understand the climate system. Thousands of papers have been published about model-based studies. Part of this research is to improve the models.
In 2000, a comparison between measurements and dozens of GCM simulations of
ENSO-driven tropical precipitation, water vapor, temperature, and outgoing longwave radiation found similarity between measurements and simulation of most factors. However, the simulated change in precipitation was about one-fourth less than what was observed. Errors in simulated precipitation imply errors in other processes, such as errors in the evaporation rate that provides moisture to create precipitation. The other possibility is that the satellite-based measurements are in error. Either indicates progress is required in order to monitor and predict such changes.
The precise magnitude of future changes in climate is still uncertain; for the end of the 21st century (2071 to 2100), for SRES scenario A2, the change of global average SAT change from AOGCMs compared with 1961 to 1990 is +3.0 °C (5.4 °F) and the range is +1.3 to +4.5 °C (+2.3 to 8.1 °F).
The IPCC's
Fifth Assessment Report asserted "very high confidence that models reproduce the general features of the global-scale annual mean surface temperature increase over the historical period". However, the report also observed that the rate of warming over the period 1998–2012 was lower than that predicted by 111 out of 114
Coupled Model Intercomparison Project
In climatology, the Coupled Model Intercomparison Project (CMIP) is a collaborative framework designed to improve knowledge of climate change. It was organized in 1995 by the Working Group on Coupled Modelling (WGCM) of the World Climate Research ...
climate models.
Relation to weather forecasting
The global climate models used for climate projections are similar in structure to (and often share computer code with)
numerical models for weather prediction, but are nonetheless logically distinct.
Most
weather forecasting
Weather forecasting or weather prediction is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather info ...
is done on the basis of interpreting numerical model results. Since forecasts are typically a few days or a week and sea surface temperatures change relatively slowly, such models do not usually contain an ocean model but rely on imposed SSTs. They also require accurate initial conditions to begin the forecast typically these are taken from the output of a previous forecast, blended with observations. Weather predictions are required at higher temporal resolutions than climate projections, often sub-hourly compared to monthly or yearly averages for climate. However, because weather forecasts only cover around 10 days the models can also be run at higher vertical and horizontal resolutions than climate mode. Currently the
ECMWF runs at resolution as opposed to the scale used by typical climate model runs. Often local models are run using global model results for boundary conditions, to achieve higher local resolution: for example, the
Met Office
The Met Office, until November 2000 officially the Meteorological Office, is the United Kingdom's national weather and climate service. It is an executive agency and trading fund of the Department for Science, Innovation and Technology and ...
runs a mesoscale model with an resolution covering the UK, and various agencies in the US employ models such as the NGM and NAM models. Like most global numerical weather prediction models such as the
GFS, global climate models are often spectral models instead of grid models. Spectral models are often used for global models because some computations in modeling can be performed faster, thus reducing run times.
Computations
Climate models use
quantitative methods to simulate the interactions of the
atmosphere
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
, oceans,
land surface
Terrain (), alternatively relief or topographical relief, is the dimension and shape of a given surface of land. In physical geography, terrain is the lay of the land. This is usually expressed in terms of the elevation, slope, and orientati ...
and
ice
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...
.
All climate models take account of incoming energy as short wave
electromagnetic radiation
In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength ...
, chiefly
visible and short-wave (near)
infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
, as well as outgoing energy as long wave (far) infrared electromagnetic radiation from the earth. Any imbalance results in a
change in temperature.
The most talked-about models of recent years relate temperature to
emissions of
greenhouse gas
Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...
es. These models project an upward trend in the
surface temperature record, as well as a more rapid increase in temperature at higher altitudes.
Three (or more properly, four since time is also considered) dimensional GCM's discretise the equations for fluid motion and energy transfer and integrate these over time. They also contain parametrisations for processes such as convection that occur on scales too small to be resolved directly.
Atmospheric GCMs (AGCMs) model the atmosphere and impose sea surface temperatures as boundary conditions. Coupled atmosphere-ocean GCMs (AOGCMs, e.g.
HadCM3,
EdGCM, GFDL CM2.X, ARPEGE-Climat) combine the two models.
Models range in complexity:
* A simple
radiant heat
Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electro ...
transfer model treats the earth as a single point and averages outgoing energy
* This can be expanded vertically (radiative-convective models), or horizontally
* Finally, (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange.
* Box models treat flows across and within ocean basins.
Other submodels can be interlinked, such as
land use
Land use is an umbrella term to describe what happens on a parcel of land. It concerns the benefits derived from using the land, and also the land management actions that humans carry out there. The following categories are used for land use: fo ...
, allowing researchers to predict the interaction between climate and ecosystems.
Comparison with other climate models
Earth-system models of intermediate complexity (EMICs)
The Climber-3 model uses a 2.5-dimensional statistical-dynamical model with 7.5° × 22.5° resolution and time step of 1/2 a day. An oceanic submodel is MOM-3 (
Modular Ocean Model) with a 3.75° × 3.75° grid and 24 vertical levels.
Radiative-convective models (RCM)
One-dimensional, radiative-convective models were used to verify basic climate assumptions in the 1980s and 1990s.
Earth system models
GCMs can form part of
Earth system model
Earth system science (ESS) is the application of systems science to the Earth. In particular, it considers interactions and 'feedbacks', through material and energy fluxes, between the Earth's sub-systems' cycles, processes and "spheres"—atmosp ...
s, e.g. by coupling
ice sheet models for the dynamics of the
Greenland
Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...
and
Antarctic ice sheet
The Antarctic ice sheet is a continental glacier covering 98% of the Antarctic continent, with an area of and an average thickness of over . It is the largest of Earth's two current ice sheets, containing of ice, which is equivalent to 61% of ...
s, and one or more
chemical transport model A chemical transport model (CTM) is a type of computer simulation, computer numerical model which typically simulates atmospheric chemistry and may be used for air pollution forecasting.
Chemical transport models and general circulation models
W ...
s (CTMs) for
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
important to climate. Thus a carbon chemistry transport model may allow a GCM to better predict
anthropogenic
Anthropogenic ("human" + "generating") is an adjective that may refer to:
* Anthropogeny, the study of the origins of humanity
Anthropogenic may also refer to things that have been generated by humans, as follows:
* Human impact on the enviro ...
changes in
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
concentrations. In addition, this approach allows accounting for inter-system feedback: e.g. chemistry-climate models allow the effects of climate change on the
ozone hole
Ozone depletion consists of two related events observed since the late 1970s: a lowered total amount of ozone in Earth, Earth's upper atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone layer) around Earth's polar ...
to be studied.
History
In 1956,
Norman Phillips developed a mathematical model that could realistically depict monthly and seasonal patterns in the
troposphere
The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...
. It became the first successful climate model. Following Phillips's work, several groups began working to create GCMs.
The first to combine both oceanic and atmospheric processes was developed in the late 1960s at the
NOAA
The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...
Geophysical Fluid Dynamics Laboratory.
By the early 1980s, the United States'
National Center for Atmospheric Research
The US National Center for Atmospheric Research (NCAR ) is a US federally funded research and development center (FFRDC) managed by the nonprofit University Corporation for Atmospheric Research (UCAR) and funded by the National Science Foundat ...
had developed the Community Atmosphere Model; this model has been continuously refined. In 1996, efforts began to model soil and vegetation types. Later the
Hadley Centre for Climate Prediction and Research
The Met Office Hadley Centre — named in honour of George Hadley — is one of the United Kingdom's leading centres for the study of scientific issues associated with climate change. It is part of, and based at the headquarters of the Met O ...
's
HadCM3 model coupled ocean-atmosphere elements.
The role of
gravity wave
In fluid dynamics, gravity waves are waves in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the oc ...
s was added in the mid-1980s. Gravity waves are required to simulate regional and global scale circulations accurately.
See also
*
Atmospheric Model Intercomparison Project (AMIP)
*
Atmospheric Radiation Measurement (ARM) (in the US)
*
Earth Simulator
*
Global Environmental Multiscale Model
*
Ice-sheet model
*
Intermediate General Circulation Model
*
NCAR
The US National Center for Atmospheric Research (NCAR ) is a US federally funded research and development center (FFRDC) managed by the nonprofit University Corporation for Atmospheric Research (UCAR) and funded by the National Science Foundat ...
*
Prognostic variable
*
Charney Report
References
* .
Further reading
*
External links
IPCC AR5, Evaluation of Climate Models* with media including videos, animations, podcasts and transcripts on climate models
* GFDL's Flexible Modeling System containing code for the climate models
*
ttp://nomads.ncdc.noaa.gov/ National Operational Model Archive and Distribution System (NOMADS)
*
Hadley Centre for Climate Prediction and Research
The Met Office Hadley Centre — named in honour of George Hadley — is one of the United Kingdom's leading centres for the study of scientific issues associated with climate change. It is part of, and based at the headquarters of the Met O ...
br>
model infoNCAR/UCAR Community Climate System Model(CESM)
Climate prediction, community modelingNASA/GISS, primary research GCM modelEDGCM/NASA: Educational Global Climate Modeling
NOAA/GFDL
MAOAM: Martian Atmosphere Observation and Modeling/
MPI
MPI or Mpi may refer to:
Science and technology Biology and medicine
* Magnetic particle imaging, a tomographic technique
* Myocardial perfusion imaging, a medical procedure that illustrates heart function
* Mannose phosphate isomerase, an enzyme ...
&
MIPT
{{DEFAULTSORT:Global Climate Model
Numerical climate and weather models
Climate forcing
Computational science
Climate change
Articles containing video clips