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Accuracy and Uncertainty in Climate Models

How do researchers know whether a computer model of Earth’s climate is accurate? To test accuracy of a model, its results are compared to observed measurements. This is often done by comparing climate data that has been directly measured over the past 100 years with a model run over the same timeframe. If the model and the actual measurements are similar, then the mathematical equations used to describe Earth dynamics are assumed to be relatively accurate.

Some uncertainty about future climate predictions based on models is due to uncertainties in the model. There are processes and feedbacks between different parts of the Earth that are not fully understood and are areas of active research. For example, the effects of clouds on climate is known to be a significant, however researchers are actively trying to better understand the effect of clouds to ensure that climate models accurately portray this part of the Earth system. Researchers work to ensure that natural processes are represented in climate models as accurately as possible, so that models can be used to make predictions of future climate that are as accurate as possible.

The majority of the uncertainty in these climate predictions is not related to natural processes. Instead, it is uncertain how much pollution humans will be adding to the atmosphere in the future. Innovations that stop or limit the amount of greenhouses gases that are produced, legislation that changes the amount of pollutants that are released, and how the growing human population lives in the future are all at least somewhat unknown. To address this, climate models are often run through various scenarios, each addressing pollution and development by humans in a different way.

According to the Intergovernmental Panel on Climate Change, the majority of climatologists agree that climate models do not perfectly represent climate processes. There is always some error in models. However, climatologists don't think that better models would change the conclusion that Earth’s average temperature is warming.

Last modified February 1, 2010 by Lisa Gardiner.

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