We know the climate is changing because that’s what climate models tell us. But what exactly is a climate model, and are they cutting-edge science or modelling madness?
What is a climate model?
Climate models are used to describe the behaviour of all, or part, of the earth’s climate.
They can be simple computer programs that describe one or more components of the climate in a specific location (how temperature changes with cloud cover in Hobart, for example). Or they can be immensely complex systems that attempt to describe the behaviour of the earth’s entire climate system.
Models that simulate the climate of the entire earth are called general circulation models, or GCMs.
The two major components of the climate are the atmosphere and the ocean. Other elements include sea ice, land surface, snow cover, lakes and rivers.
The movements of the atmosphere and ocean currents are described using the Navier-Stokes equations.
These mathematical equations have been used for more than 200 years to describe the movement of fluids. As well as being used to model climate systems, these equations are used by engineers to describe water flow in pipes and air flow around objects such as aeroplane wings.
Can we predict the future?
The future state of the climate has been of interest to people for thousands of years. The Babylonians used cloud patterns to forecast the weather as far back as 650 BC, and Chinese and Indian astronomers independently developed weather prediction methods by 300 BC.
The practice of using a mathematical model to predict the weather has been around since the 1920s, but it wasn’t until the advent of computers in the 1950s that numerical weather predictions first produced realistic results. The first GCMs were developed in the late 1960s.