Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Climate Model shopping experience:

1. Compare - without doubt the biggest advantage that the Climate Model offers shoppers today is the ability to compare thousands of Climate Model at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Climate Model? Wrong! If the Climate Model is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Climate Model then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Climate Model? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Climate Model and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Climate Model wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Climate Model then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Climate Model site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Climate Model, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Climate Model, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

Climate models use quantitative methods to simulate the interactions of the Earth's 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 imbalance results in a change in the average temperature of the earth.

The most talked-about models of recent years have been those relating temperature to emissions of carbon dioxide (see greenhouse gas). These models project an upward trend in the surface temperature record, as well as a more rapid increase in temperature at higher altitudes.

Models can range from relatively simple to quite 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
• finally, (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange.

This is not a full list; for example "box models" can be written to treat flows across and within ocean basins.

Zero-dimensional models A very simple model of the radiative equilibrium of the Earth is

(1-a)S \pi r^2 = 4 \pi r^2 \epsilon \sigma T^4

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

• S is the solar constant - the incoming solar radiation per unit area - about 1367 W·m-2
• a is the Earth's average albedo, measured to be 0.3
• r is Earth's radius — approximately 6.371×106m
• pi is well known, approximately 3.14159
• \sigma is the Stefan-Boltzmann constant — approximately 5.67×10-8 J·K-4·m-2·s-1
• \epsilon is the effective emissivity of earth, about 0.612

The constant πr2 can be factored out, giving

(1-a)S = 4 \epsilon \sigma T^4

This yields an average earth temperature of 288 K . This is because the above equation represents the effective radiative temperature of the Earth (including the clouds and atmosphere). The use of effective emissivity accounts for the greenhouse effect.

This very simple model is quite instructive, and the only model that could fit on a page. For example, it easily determines the effect on average earth temperature of changes in solar constant or change of albedo or effective earth emissivity. Using the simple formula, the percent change of the average amount of each parameter, considered independently, to cause a one degree Celsius change in steady-state average earth temperature is as follows:

Solar constant 1.4%Albedo 3.3%Effective emissivity 1.4%

The average emissivity of the earth is readily estimated from available data. The emissivities of terrestrial surfaces are all in the range of 0.96 to 0.99 (except for some small desert areas which may be as low as 0.7). Clouds, however, which cover about half of the earth’s surface, have an average emissivity of about 0.5 (which must be reduced by the fourth power of the ratio of cloud absolute temperature to average earth absolute temperature) and an average cloud temperature of about 258 K . Taking all this properly into account results in an effective earth emissivity of about 0.64 (earth average temperature 285 K).

This simple model readily determines the effect of changes in solar output or change of earth albedo or effective earth emissivity on average earth temperature. It says nothing, however about what might cause these things to change. Zero-dimensional models do not address the temperature distribution on the earth or the factors that move energy about the earth.

Radiative-Convective Models The zero-dimensional model above, using the solar constant and given average earth temperature, determines the effective earth emissivity of long wave radiation emitted to space. This can be refined in the vertical to a zero-dimensional radiative-convective model, which considers two processes of energy transport:

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

The radiative-convective models have advantages over the simple model: they can determine the effects of varying greenhouse gas concentrations on effective emissivity and therefore the surface temperature. But added parameters are needed to determine local emissivity and albedo and address the factors that move energy about the earth.

Links:

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

Higher Dimension Models The zero-dimensional model may be expanded to consider the energy transported horizontally in the atmosphere. This kind of model may well be Zonal and meridional averaged. This model has the advantage of allowing a rational dependence of local albedo and emissivity 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

EMICs (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.

• http://www.pik-potsdam.de/emics/

GCMs (Global Climate Models or General circulation models) 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 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, 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 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.

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 .

See also

• Climateprediction.net
• Tropical cyclone prediction model
• GFDL CM2.X

Climate models on the web

• Dapper/DChart - plot and download model data referenced by the Fourth Asssessment Report (AR4) of the Intergovernmental Panel on Climate Change .
• http://www.hadleycentre.gov.uk/research/hadleycentre/models/modeltypes.html - Hadley Centre for Climate Prediction and Research - general info on their models
• http://www.ccsm.ucar.edu/ - NCAR/University Corporation for Atmospheric Research 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
• http://nomads.gfdl.noaa.gov/CM2.X/ - NOAA / Geophysical Fluid Dynamics Laboratory CM2 global climate model info and model output data files
• http://www.climate.uvic.ca/ - University of Victoria Global climate model, free for download. Leading researcher was a contributing author to the recent IPCC report on climate change.

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
• Basic Radiation Calculations - The Discovery of Global Warming
• Robinson, Peter J. and Henderson-Sellers, Ann, Contemporary Climatology, Pearson Education, 1999

Climate models use quantitative methods to simulate the interactions of the Earth's 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 imbalance results in a change in the average temperature of the earth.

The most talked-about models of recent years have been those relating temperature to emissions of carbon dioxide (see greenhouse gas). These models project an upward trend in the surface temperature record, as well as a more rapid increase in temperature at higher altitudes.

Models can range from relatively simple to quite 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
• finally, (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange.

This is not a full list; for example "box models" can be written to treat flows across and within ocean basins.

Zero-dimensional models A very simple model of the radiative equilibrium of the Earth is

(1-a)S \pi r^2 = 4 \pi r^2 \epsilon \sigma T^4

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

• S is the solar constant - the incoming solar radiation per unit area - about 1367 W·m-2
• a is the Earth's average albedo, measured to be 0.3
• r is Earth's radius — approximately 6.371×106m
• pi is well known, approximately 3.14159
• \sigma is the Stefan-Boltzmann constant — approximately 5.67×10-8 J·K-4·m-2·s-1
• \epsilon is the effective emissivity of earth, about 0.612

The constant πr2 can be factored out, giving

(1-a)S = 4 \epsilon \sigma T^4

This yields an average earth temperature of 288 K . This is because the above equation represents the effective radiative temperature of the Earth (including the clouds and atmosphere). The use of effective emissivity accounts for the greenhouse effect.

This very simple model is quite instructive, and the only model that could fit on a page. For example, it easily determines the effect on average earth temperature of changes in solar constant or change of albedo or effective earth emissivity. Using the simple formula, the percent change of the average amount of each parameter, considered independently, to cause a one degree Celsius change in steady-state average earth temperature is as follows:

Solar constant 1.4%Albedo 3.3%Effective emissivity 1.4%

The average emissivity of the earth is readily estimated from available data. The emissivities of terrestrial surfaces are all in the range of 0.96 to 0.99 (except for some small desert areas which may be as low as 0.7). Clouds, however, which cover about half of the earth’s surface, have an average emissivity of about 0.5 (which must be reduced by the fourth power of the ratio of cloud absolute temperature to average earth absolute temperature) and an average cloud temperature of about 258 K . Taking all this properly into account results in an effective earth emissivity of about 0.64 (earth average temperature 285 K).

This simple model readily determines the effect of changes in solar output or change of earth albedo or effective earth emissivity on average earth temperature. It says nothing, however about what might cause these things to change. Zero-dimensional models do not address the temperature distribution on the earth or the factors that move energy about the earth.

Radiative-Convective Models The zero-dimensional model above, using the solar constant and given average earth temperature, determines the effective earth emissivity of long wave radiation emitted to space. This can be refined in the vertical to a zero-dimensional radiative-convective model, which considers two processes of energy transport:

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

The radiative-convective models have advantages over the simple model: they can determine the effects of varying greenhouse gas concentrations on effective emissivity and therefore the surface temperature. But added parameters are needed to determine local emissivity and albedo and address the factors that move energy about the earth.

Links:

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

Higher Dimension Models The zero-dimensional model may be expanded to consider the energy transported horizontally in the atmosphere. This kind of model may well be Zonal and meridional averaged. This model has the advantage of allowing a rational dependence of local albedo and emissivity 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

EMICs (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.

• http://www.pik-potsdam.de/emics/

GCMs (Global Climate Models or General circulation models) 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 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, 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 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.

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 .

See also

• Climateprediction.net
• Tropical cyclone prediction model
• GFDL CM2.X

Climate models on the web

• Dapper/DChart - plot and download model data referenced by the Fourth Asssessment Report (AR4) of the Intergovernmental Panel on Climate Change .
• http://www.hadleycentre.gov.uk/research/hadleycentre/models/modeltypes.html - Hadley Centre for Climate Prediction and Research - general info on their models
• http://www.ccsm.ucar.edu/ - NCAR/University Corporation for Atmospheric Research 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
• http://nomads.gfdl.noaa.gov/CM2.X/ - NOAA / Geophysical Fluid Dynamics Laboratory CM2 global climate model info and model output data files
• http://www.climate.uvic.ca/ - University of Victoria Global climate model, free for download. Leading researcher was a contributing author to the recent IPCC report on climate change.

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
• Basic Radiation Calculations - The Discovery of Global Warming
• Robinson, Peter J. and Henderson-Sellers, Ann, Contemporary Climatology, Pearson Education, 1999

ClimatePrediction.Net gateway
This page attempts to give you a brief overview of how climate models work, and some details about the models used in the climate prediction.net experiment.

ClimatePrediction.Net gateway
Large-scale simulation where each participant is given one slightly different scenario to run. Those that successfully model past weather patterns will be more likely to accurately ...

Climate model - Wikipedia, the free encyclopedia
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 ...

BBC - Science & Nature - Climate Change
We asked for your spare computing power to predict future climate. Developed for the BBC by climate scientists, led by Oxford University, using the Met Office climate model.

Research Projects/Climate Model Validation
Research Projects/Climate Model Evaluation The Climatic Research Unit has a contract with the UK Department of the Environment, Transport and the Regions (DETR;

ChooseClimate: Interactive Java Climate Model
Interactive model linking Climate Science and Policy, from emissions to impacts -adjust parameters by dragging controls with your mouse

Met Office: Types of climate models
Climate Change is a global issue and the Met Office Hadley Centre is leading international research into what could happen under climate change, and the impacts on current and ...

Java Climate Model
JCM4 Old, stable, documented, version, 24 th March 2004 for beginners. JCM5 New developing version (in Java 1.5), 20 th March 2007 partially documented, for experts

BBC NEWS | Science/Nature | Ten-year climate model unveiled
Scientists unveil a climate model offering 10-year forecasts of global warming, compared to existing long-term ones.

BBC NEWS | Science/Nature | Climate model shows dual cause
UK scientists say both natural and human influences have caused the world to warm. ... By environment correspondent Alex Kirby. UK scientists say only a combination of natural and ...