Other parts of the model

Other Parts of the Model

The model has a few other parts to it, including the initial temperature of the Earth, which determines how much thermal energy is stored in the earth at the beginning of the model run. It also includes some other features that allow you to change the solar input and the part of the greenhouse effect due to CO₂. We use the standard assumption (which is itself based on some physics calculations) that for each doubling of the CO₂ concentration, there is an increase of 4 W/m² in the greenhouse effect. This is often called the greenhouse forcing due to CO₂. In terms of our Eout curve shown in Figure 2 above, this shifts the red curve downwards — so less energy is emitted, and thus more is retained by the Earth. Let’s consider how this works — if we start with 200 ppm of CO₂ and increase it to 800 ppm, that represents 2 doublings (from 200 to 400 and then from 400 to 800), so we would get 8 W/m² of greenhouse forcing.

One unit of time in this model is equal to a year, but the program will actually calculate the energy flows and the temperature every 0.1 years.

Now that you have seen how the model is constructed, let’s explore it by doing some experiments. Here is the link to the model.