Global Climate Models

Researchers use global climate models to calculate what will happen to temperatures, winds, water currents, and other parameters in each cube under various scenarios, for instance a doubling of the current atmospheric carbon dioxide concentration. These calculations are used to predict the likely impacts of global warming, including temperature rises and rates of change.

Essentially, a global climate model is a computerized grid of millions of mathematically connected cubes covering the Earth. Cubes represent oceans, forests, land, sea ice, and the atmosphere, each with its own separate model, which climate modellers combine to project how global systems interact to influence the planet’s climate.

Each cube represents a collection of formulas mathematically describing processes that are relevant to climate within that area. Many of these formulas are based on rudimentary physics, such as the laws of gravity and Newton’s laws of motion. These equations are combined to determine how changes in greenhouse gases due to use of fossil fuels or forest coverage will affect the climate.

Most current models are based on research into how the carbon cycle operates, and currently ignore positive feedback mechanisms. The most sophisticated models are employed by the Intergovernmental Panel on Climate Change (IPCC).

Much of what will govern the climate at a given point can be well addressed, but other components remain difficult to model. For instance cloud formations are notoriously complex, and so the effect of clouds on the future climate remain a source of modelling uncertainty.

Once all the equations for the cubes are set, researchers run various types of experiments through the model, such as projecting potential future climates based on scenarios with various levels of human fossil fuels use, population and deforestation. It is impossible to verify what humans are going to do in the future, so filling in these blanks is one of the largest sources of uncertainty in climate modelling.

Climate modelling in not a perfect science, but the virtual planets they describe are still the best available tests for studying present and future climate change.

References

Mark Schrope, ‘Climate Change Models: understanding the basics’, Yale Forum on Climate Change and the Media, 20 January 2009,
http://www.yaleclimatemediaforum.org/2009/01/climate-change-models-understanding-the-basics/

David A. Randall et al., ‘Climate Models and their Evaluation’, in IPCC, Climate Change: the Physical Science Basis, 2007, www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf

David A. Randall et al., ‘Climate Models and their Evaluation’, in IPCC, Climate Change: the Physical Science Basis, 2007, www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf