The climate models to which NASA refers are powerful computer programs used to simulate climate and predict future climate changes. Models can be used to simulate temperature changes that occur from both natural and anthropogenic causes. Scientists enter data on different conditions, such as atmospheric concentrations of greenhouse gases, ocean currents, cloud cover, energy from the sun, and ocean circulation, as well as others. Then, as they change and adjust the variables, they can simulate what might happen when actual climate conditions change. NASA compares climate models to the computer programs used by detectives to envision what
This illustration mimics a computer model used to predict climate change. The melting earth suggests global warming is a serious threat.
This illustration mimics a computer model used to predict climate change. The melting earth suggests global warming is a serious threat.
A scientist explains a general circulation model generated by a supercomputer. Scientists debate the value of computer model predictions.
A scientist explains a general circulation model generated by a supercomputer. Scientists debate the value of computer model predictions.
missing persons would look like years after their disappearance. In the same way the detective programs are constructed on information about people's faces, climate models are constructed based on data that relate to the earth's climate.
There are many different types of climate models. The simplest models can be run on personal computers, and are designed to focus on one particular time frame, or to investigate a specific phenomenon. The most sophisticated climate models are supercomputers known as general circulation models (GCMs). Climate models have evolved from the same sort of computer programs that are used to make weather forecasts. Richard C.J. Somerville says that just as people criticize meteorologists when weather predictions are wrong, some global warming skeptics denounce climate models as useless—and he insists that is not true. He also says that just as weather simulation programs have improved markedly over time, climate models are also being improved and perfected. He shares his perspective about their use for predicting a future climate: "The model in the end is a computer program. We can't take the atmosphere or the whole planet and put it in a test tube and do experiments on it. So instead, we simulate it in a computer. That's turned out to be the best way of incorporating all the various complexities." 31