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. Layers of Atmosphere (NOAA) Air redirects here. ... [[Image:http://www. ...

The most talked-about models of recent years have been those relating air temperature to emissions of carbon dioxide (see greenhouse gas). These models predict an upward trend in the surface temperature record, as well as a more rapid increase in temperature at higher altitudes. Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... The historical temperature record shows the fluctuations of the temperature of the atmosphere and the oceans throughout history, and in particular since 1850. ...

Models can range from relatively simple to quite complex:

• Simple back-of-the-envelope calculations of the radiative temperature treat the earth as a single point
• this can be expanded vertically (radiative-convective models), or horizontally (energy balance models)
• finally, (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for fluid motion.

This is not a full list; for example "box models" can be written to treat flows across and within ocean basins. The phrase back-of-the-envelope refers to rough calculations that, while not rigorous, test or support a point. ... An icebreaker navigates through young (1 year) sea ice Sea ice is formed from ocean water that freezes. ... ...

Zero-dimensional models

It is possible to obtain a very simple model of the radiative equilibrium of the Earth by writing

(1 − a)Sπr² = 4πr²sT⁴

where

• the left hand side represents the incoming energy from the Sun
• the right hand side represents the outgoing energy from the Earth, calculated from the Stefan-Boltzmann law assuming a constant radiative temperature, T, that is to be found,

and Stefan-Boltzmann law (also Stefans law) states that tom is a brain the total energy radiated per unit surface area of a black body in unit time (black-body irradiance), (or the energy flux density (radiant flux) or the emissive power), j* is directly proportional to the fourth power...

• S is the solar constant - the incoming solar radiation per unit area - about 1367 W·m^-2
• a is the Earth's average albedo, approximately 0.37 to 0.39
• r is Earth's radius — approximately 6.371×10⁶m
• π is well known, approximately 3.14159
• s is the Stefan-Boltzmann constant — approximately 5.67×10^-8 J·K^-4·m^-2·s^-1

The constant πr² can be factored out, giving Solar irradiance spectrum at top of atmosphere. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... Albedo is the measure of reflectivity of a surface or body. ... Lower-case Ï€ (the lower case letter is usually used for the constant) The mathematical constant Ï€ is an irrational number, approximately equal to 3. ... The Stefan-Boltzmann constant (also Stefans constant), denoted with a Greek letter σ, is a derivable physical constant, the constant of proportionality between the total energy radiated per unit surface area of a black body in unit time and the fourth power of the thermodynamic temperature, as per the...

(1 − a)S = 4sT⁴

which yields a value of 246 to 248 kelvins — about -27 to -25 °C — for the Earth's average temperature T. This is approximately 35 kelvins colder than the average surface temperature of 282 K. This is primarily because the above equation attempts to represent the radiative temperature of the Earth, and the average radiative level is well above the surface. The difference between the radiative and surface temperatures is the natural greenhouse effect. The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... The greenhouse effect, first discovered by Joseph Fourier in 1824, and first investigated quantitatively by Svante Arrhenius in 1896, is the process by which an atmosphere warms a planet. ...

This very simple model is quite instructive, and the only model that could fit on a page. But it produces a result we are not really interested in — the radiative temperature — rather than the more useful surface temperature. It also contains the albedo as a specified constant, with no way to "predict" it from within the model ...

Radiative-Convective Models

The zero-dimensional model above predicts the temperature of an imaginary layer where long wave radiation is emitted to space. This can be extended in the vertical to a one dimensional radiative-convective model, which simplifies the atmosphere to consider only two processes of energy transport:

• upwelling and downwelling radiative transfer through atmospheric layers
• upward transport of heat by convection (especially important in the lower troposphere).

The radiative-convective models have advantages over the simple model: they can tell you the surface temperature, and the effects of varying greenhouse gas concentrations on the surface temperature. But they need added parameters, and still represent by one point the horizontal surface of the earth. The Troposphere is the lowermost portion of Earths atmosphere. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ...

Links:

• http://www.giss.nasa.gov/gpol/abstracts/1980/WangStone.html
• http://www.grida.no/climate/ipcc_tar/wg1/258.htm

Energy Balance Models

Alternatively, the zero-dimensional model may be expanded horizontally to consider the energy transported horizontally in the atmosphere. This kind of model may well be zonally averaged. This model has the advantage of allowing a plausible dependence of albedo on temperature - the poles can be allowed to be icy and the equator warm - but the lack of true dynamics means that horizontal transports have to be specified.

• http://www.shodor.org/master/environmental/general/energy/application.html

EMIC's (Earth-system Models of Intermediate Complexity

Depending on the nature of questions asked and the pertinent time scales, there are, on the one extreme, conceptual, more inductive models, and, on the other extreme, general circulation models operating at the highest spatial and temporal resolution currently feasible. Models of intermediate complexity bridge the gap. One example is the Climber-3 model. Its atmosphere is a 2.5-dimensional statistical-dynamical model with 7.5° × 22.5° resolution and time step of 1/2 a day; the ocean is MOM-3 (Modular Ocean Model) with a 3.75° × 3.75° grid and 24 vertical levels. ... The Modular Ocean Model (MOM) is a three-dimensional ocean circulation model designed primarily for studying the ocean climate system. ...

• http://www.pik-potsdam.de/emics/

GCMs (Global Climate Models or General circulation models)

Main article: Global climate model

Three (or more properly, four) dimensional GCM's discretise the equations for fluid motion and integrate these forward in 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. Coupled atmosphere-ocean GCMs (AOGCMs, e.g. HadCM3, EdGCM) combine the two models. 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. HadCM3 (Hadley Centre Coupled Model, version 3) is a coupled atmosphere-ocean general circulation model (AOGCM) developed at the Hadley Centre and described by Gordon et al (2000) and Pope et al (2000). ... EdGCM is an educational version of a global climate model (GCM) that has been ported for use on desktop computers and integrated with a relational database, a graphical user interface, and scientific visualization utllities, all of which are aimed at helping improve the quality of teaching and learning of climate...

Most recent simulations show "plausible" agreement with the measured temperature anomalies over the past 150 years, when forced by observed changes in "Greenhouse" gases and aerosols, but better agreement is achieved when natural forcings are also included [1] [2].

See also

• Global climate model
• Tropical cyclone prediction model
• Radiative forcing
• Climate change
• Global warming

... Hurricane Epsilon defied and frustrated forecasters by persisting in a hostile environment for a remarkably long time A tropical cyclone prediction model is a computer program that uses meteorological data to predict the motion and intensity of tropical cyclones. ... The generalised concept of radiative forcing in climate science is any change in the radiation (heat) entering the climate system or changes in radiatively active gases. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years Climate change refers to the variation in the Earths global climate or regional climates over time. ... Global mean surface temperatures 1856 to 2005; this map shows mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming refers to the observed increases in the average temperature of the Earths atmosphere and oceans in recent...

Climate models on the web

• http://www.mmm.ucar.edu/mm5/mm5-home.html - University Corporation for Atmospheric Research - NCAR MM5 Mesoscale model
• http://www.hadleycentre.gov.uk/research/hadleycentre/models/modeltypes.html - Hadley Centre - general info on their models
• http://www.cgd.ucar.edu/csm/ - NCAR/UCAR Community Climate System Model (CCSM)
• http://www.climateprediction.net - do it yourself climate prediction
• http://edgcm.columbia.edu/ - a NASA/GISS global climate model (GCM) with a user-friendly interface for PCs and Macs
• http://www.cccma.bc.ec.gc.ca/ - CCCma model info and interface to retrieve model data

The National Center for Atmospheric Research (NCAR), in Boulder, Colorado, was established in 1960 to serve as a focus for United States research on atmospheric and related science problems, including climate change, atmospheric chemistry, changes in atmospheric composition, mesoscale and microscale meteorology, Earth-Sun interactions, weather formation and forecasting, and... The Hadley Centre for Climate Prediction and Research, which is part of the Met Office, provides a focus in the United Kingdom for the scientific issues associated with climate change. ... The National Center for Atmospheric Research (NCAR), in Boulder, Colorado, was established in 1960 to serve as a focus for United States research on atmospheric and related science problems, including climate change, atmospheric chemistry, changes in atmospheric composition, mesoscale and microscale meteorology, Earth-Sun interactions, weather formation and forecasting, and... UCAR is a nonprofit corporation formed in 1959 by research institutions with doctoral programs in the atmospheric and related sciences. ... CCCma (Canadian Centre for Climate Modeling and Analysis) is a division of the Climate Research Branch of the Meteorological Service of Canada of Environment Canada based out of the University of Victoria, Victoria, British Columbia. ...

References

• (IPCC 2001 section 8.3) - on model hierarchy
• (IPCC 2001 section 8) - much information on coupled GCM's
• Coupled Model Intercomparison Project
• On the Radiative and Dynamical Feedbacks over the Equatorial Pacific Cold Tongue