... Unfortunately, I cannot see that... :-( I don't seem to be able to access any parts of the site that I used to be able to access: climateprediction.net, my account page, the forums, etc. ...

This thread deals with science information about the applications available though your preferences. If you are more interested in computing information (and the way the preferences work), see http://www.climateprediction.net/board/viewtopic.php?p=66108#66108

Science Information

General Why

Climate change, and our response to it, is an issue of global importance, affecting food production, water resources, ecosystems, energy demand, insurance costs and much else. There is a broad scientific consensus that the Earth will probably warm over the coming century; climateprediction.net should, for the first time, tell us what is most likely to happen.

The project is therefore aimed more at producing probabilistic estimates than a single best estimate model. To do this, the project needs to run lots of slightly different versions of possible future climates. It does this by varying Parameters of the model.

There is an index of much more science information on the CPDN website at Climate science explained including objectives, strategy etc. For more general information about climate science see the climate science README.

After this brief introduction this page will now look at the three applications available on your preferences page. (Pre 21 December 2007 there were only two options. The third model was previously available from the Seasonal attribution site only but has now been moved to here.):

The three models are:

1. Equilibrium Slab model (UK Met Office HADSM3) - 45 model years

2. Transient (or control) Coupled model (UK Met Office HADCM3) - 160 or 80 model years
3. Seasonal Attribution Model (UK Met Office HADAM3) - 1 year high resolution



1. Equilibrium Slab model (UK Met Office HADSM3) - 45 model years

Explanation of terms:

Follow links for meanings of Equilibrium and Slab.

HADSM3 stands for Hadley Centre (The climate division of the UK Met Office) Slab Model version 3. So this is the name of the model climateprediction.net are using. The Hadley centre is responsible for developing the model, climateprediction.net is just using it.

Why this type of Model?

Climateprediction.net wanted to start with an equilibrium slab model to:

1. Investigate climate sensitivity. This has led to a few papers including

Stainforth et al. Uncertainty in predictions of the climate response to rising levels of greenhouse gases, Nature, 433, pp.403-406, January 2005.

Piani et al. Constraints on climate change from a multi-thousand member ensemble of simulations, Geophysical Review Letters, 32, L23825, December 2005.

For a fuller list see http://www.climateprediction.net/science/scientific_papers.php

2. It would help gather information to reduce the computing time needed to set up the Transient coupled models.

Sufficient of these model runs for the above purposes had been received when the Sulphur Cycle Model was launched. Hence it was withdrawn (Except for classic which was kept open for the Open University course).

Why is it being re-released? / Number of runs needed

The initial release only set each parameter at one of three values. If the effect of changes in the parameters had only simple linear effects then it would be possible to interpolate for parameter values between the ones handed out easily. As expected, the relationships have been shown to be nonlinear. Ben Sanderson has developed a neural net to estimate these nonlinear interactions. They now want to run some more models using hopefully better parameter values as estimated by the neural net to see if these do produce better models and see how well the neural net manages to do at estimating the nonlinear relationships. If successful, this will be used as an active parameter selection technique for future ensembles using HadGEM (a higher resolution model).

Also Falk Niehörster (Free University of Berlin) is interested in doing comparisons of the hopefully optimised models with a different model (the German ECHAM5 model).

Just 1000 are needed.

Further details of the model

The model is split into 3 phases of 15 years each. These are a calibration phase to teach the slab ocean what values to take to get a realistic and steady climate in the absence of changing forcings. A control phase checks that the values obtained from the calibration phase do result in a steady climate. The final phase introduces a forcing of doubling the CO2 level.

The resolution of the model is 96 longitude by 73 latitude by 19 atmospheric layers.

More advanced information:
Hadley Centre Types of Climate Models
Hadley Centre QUMP project using HADSM3. This is a sister project to CPDN.




2. Transient (or control) Coupled model (UK Met Office HADCM3) - 160 or 80 model years

Explanation of terms:

Follow links for meanings of Transient and Coupled and control.

HadCM3 stands for
Hadley Centre (The climate division of the UK Met Office) Coupled Model version 3. So this is the name of the model climateprediction.net are using. The Hadley centre is responsible for developing the model, climateprediction.net is just using it.

You may get a transient model or you may get a control model. One is of no use without the other as the scientists want to see what the differences are. This is because coupled models take a very long time for the ocean to get into an equilibrium state. If this has not been fully done the model may drift. Comparing to a control model is a way of eliminating this drift and reduces the total computation effort required.

Why this type of Model?

After climateprediction.net had investigated climate sensitivity with an equilibrium slab model, they want to move on to exploring how climate would really evolve with time (The instantaneous doubling of CO2 carried out in the slab model is not realistic). This requires a transient model and more realistic forcings. It also requires a more realistic ocean that can change dynamically hence a coupled model was needed.

This model has stayed at the same resolution. For some impact studies a higher resolution model might be needed. However, halving the length of a cell takes 16 times as much computing time (2*2*2 for 3 spatial dimensions and the timesteps need to be half as long as well). Such high resolution models and high computing requirements are not needed for all purposes. Also, it may well be best to study impacts by a large number of one year models starting from data for 2040 and/or 2080 provided by one of these lower resolution models.

Number of runs needed

A few thousand are wanted to explore a limited set of forcing scenarios and parameters. However, it is easily possible to explore more scenarios and/or more parameters and/or more values for some of the parameters to add many more models that could usefully be run.

Further details of the model

The model starts in 1920 running a hindcast for 80 years. It then continues to run a forecast. The resolution of the model is 96 longitude by 73 latitude by 19 atmospheric layers. There are 20 ocean layers.

The 80 year model starts in 2000 so it does not do a hindcast. This allows different forcing scenarios to be used with model physics that have already been run to 2000. There is no point repeating work that has already been done.

More advanced information:
Hadley Centre Types of Climate Models


3. Seasonal Attribution Model (UK Met Office HADAM3) - 1 year high resolution

Draft info (ie we don't think this had expert review)

The main source for info on this model included here is
this attribution site thread post by Pardeep Pall.

Explanation of terms:

Follow links for meanings of Atmosphere Model.

HadAM3 stands for
Hadley Centre (The climate division of the UK Met Office) Atmosphere Model version 3. So this is the name of the model climateprediction.net are using. The Hadley centre is responsible for developing the model, climateprediction.net is just using it.

You may get an Industrial or Non-Industrial model. For the first experiment (investigating the UK autumn floods in 2000), The Industrial climate models the year 2000. The year starts in March well before the UK autumn floods. Slight changes in the initial conditions change the way the model develops and only rarely will an extreme event like the UK autumn floods appear in the models.

The Non-Industrial models are not 'Pre-Industrial' meaning what the climate would look like in 1750. The models are of the year 2000 but dehumanised. This means how it would be expected that the climate would be if we went back to 1900 and allowed the climate to develop for 100 years with non human influences only.

As there is uncertainty about what this Non-Industrial climate would be like there are a few (at least 5?) different sets of ocean temperature patterns used, based on simulations on many different types of climate model.

Subsequent experiments will be for different time periods and regions.

See also
http://attribution.cpdn.org/about.php and
http://attribution.cpdn.org/extension.php



Why this type of Model?

The aim is to determine the extent to which the risk of occurrence of extreme weather events is attributable to human-induced climate change. The first analysis is directed at the flooding in the UK in Autumn 2000.

The atmosphere has a high spatial resolution. This is necessary when looking at impacts as larger cells may well average out detail that is important. This is probably even more important when looking at extreme events and also when looking at precipitation rather than temperature.

There is a slab ocean which is not allowed to vary from provided sea surface temperatures provided. As we are only modelling one year ocean responses are not wanted. This also makes it easier to specify sea surface temperatures and get the model to react sensibly and not drift away from these specified temperatures.


Number of runs needed

The aim is to complete around 10,000 climate model simulations of each of the Autumn 2000 climates. There is one Industrial and at least 5? such Non-Industrial climates. (Perhaps more can usefully be added as has previously happened with the Jan 07 Extension.) The industrial (A2000) models are identified by _a_ in the model name, whereas the nonindustrial (NIA2000) models have an _n_ in the model name.

Further details of the model

The first experiment's model starts in March 00 and runs for 1 model year. It has a horizontal resolution of approximately 100km2 at mid-latitudes enabling it to reasonably capture the storms and weather patterns associated with the Autumn 2000 UK flooding. There is a single slab ocean layer. This just maintains the sea surface temperatures it has been told to maintain in the same way as phase 1 of the slab model.

The sea surface temperatures have been found to be important to extreme precipitation in the climate model, and this has lead to extra model (such as the Japanese MIROC 3.2) being used to generate different sea surface temperature patterns to further test this dependance.

This first experiment is most interested in certain regions of the globe (Western Europe, India, Southern Africa, and Northwestern USA), so when the climate is uploaded at the end of the model, the climate for these areas is uploaded to the server in greater detail).

What is climateprediction.net?
Climateprediction.net is the largest experiment to try and produce a forecast of the climate in the 21st century.
To do this, we need people around the world to give us time on their computers - time when they have their computers switched on, but are not using them to their full capacity.
Read more about the experiment

Why?
Climate change, and our response to it, are issues of global importance, affecting food production, water resources, ecosystems, energy demand, insurance costs and much else.
There is a broad scientific consensus that the Earth will probably warm over the coming century; climateprediction.net should, for the first time, tell us what is most likely to happen.
Read more about climate science

What do we want you to do?
You can download a climate model from this website. It will run automatically as a background process on your computer whenever you switch your computer on.
It should not affect any other tasks you use your computer for.
As the model runs, you can watch the weather patterns on your, unique, version of the world evolve.
The results are sent back to us via the internet, and you will be able to see a summary of your results on this web site.
Climateprediction.net uses the same underlying software, BOINC, as many other distributed computing projects.
If you like, you can participate in more than one project at a time.
Go to Boinc / climateprediction.net download page

If you are in the climate research community and are interested in participating in the experiment in a research capacity, the research pages provide some basic background material.