Introduction to a Simple Planetary Climate Model

Introduction to a Simple Planetary Climate Model

Our first climate model calculates how much energy is received and emitted (given off) by our planet, and how the average temperature relates to the amount of thermal energy stored. The complete model is shown below, with three different sectors of the model highlighted in color:

Figure 1. A very simple STELLA model of Earth’s climate system. The three colored sectors show the parts of the model that keep track of the energy coming in to the Earth from the Sun, the energy leaving the Earth through emitted heat, and the average surface temperature of the Earth.

Click for a text description of the STELLA Diagram for the Planetary Climate Model.

This STELLA diagram visually represents the planetary climate model by categorizing key climate-related variables into three main groups: Energy In (yellow area), Temperature (red area), and Energy Out (blue area).

• Energy In (Yellow Area):

  • Factors affecting incoming solar energy: Solar Constant, Albedo, Surf Area.
  • These variables influence Insolation, which directs energy to Earth Heat.

• Temperature (Red Area):

  • Includes Ocean Depth, Water Density, and Heat Capacity, which influence Temperature.
  • Temperature interacts with Earth Heat and contributes to heat exchange processes.

• Energy Out (Blue Area):

  • Outgoing energy factors include Heat Emitted, LW Int, and LW Slope.
  • Earth Heat emits energy, balancing the system.

Arrows show the flow of energy and interactions between these factors. The diagram helps illustrate the components regulating planetary climate.

Credit: David Bice @ Penn State is licensed under CC-BY-NC-4.0

First, let’s define a few terms that you might not be familiar with.

Insolation —stands for Incoming Solar Radiation, which is a fancy way of saying sunlight or solar energy.

Albedo — the fraction of light reflected from some material; 0 would be a perfectly black object (no reflected light) and 1 would be a perfectly white object (no light absorbed).

Heat capacity — this is the amount of energy (units are Joules) needed to raise 1 kilogram of some material 1°C.

Ocean Depth — this is the depth of the part of the ocean that is involved in climate over short time scales of decades, the part of the ocean exchanges energy with the atmosphere. While the whole ocean has an average depth of ~4000 m, the part we worry about here has a depth of less than 500 m.

LW Int and LW slope — these are parameters used to describe the relationship between the average planetary temperature and the amount of long-wavelength (infrared, or thermal) energy emitted by the planet; more details are provided below.