The greenhouse effect and Earth's energy balance
PhysicsPhysics & the EnvironmentAges 15–16
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Physics & the Environment
Whether Earth warms or cools depends on the balance between the solar energy it absorbs and the infrared radiation it emits. Adjust the greenhouse-gas level, surface reflectivity (clouds, ice), and the solar constant to see how the equilibrium temperature changes — along with the ice-melt feedback loop that makes Earth absorb even more heat.
Lesson: Physics and environmental science: Earth's energy budget
What it shows
Earth's average temperature settles where the energy absorbed from sunlight equals the energy radiated to space as infrared. The simulation uses a simple one-layer atmosphere model: Earth absorbs (1 − a)·S/4 of the solar constant S, where a is the albedo, and the Stefan–Boltzmann law σT⁴ sets how much it emits. Greenhouse gases absorb outgoing infrared and radiate part of it back to the surface, so the surface must be warmer than the effective temperature to stay in balance. An optional ice-albedo feedback lowers the albedo as the planet warms.
How to use
Press Pre-industrial and then Current level to compare the surface temperature and the energy-flow arrows. Move the greenhouse gas slider while keeping the albedo fixed, then return and change only the surface reflectivity. Switch the ice-melt feedback off and on with the same greenhouse-gas setting and compare the final temperatures to see how a feedback loop amplifies a small change. The solar constant can be varied to model changes in the Sun's output.
Parameters you can change
- Greenhouse gas level (× pre-industrial) 0.5–3 ×
- Surface reflectivity (albedo) 0.1–0.6
- Solar constant 1200–1500 W/m²
- Enable ice-melt feedback
Questions to explore
- Why do greenhouse gases let most sunlight through but reduce the infrared energy escaping to space?
- At the same greenhouse-gas level, how much warmer does the surface become when the ice-melt feedback is switched on?
- Which cools Earth more in this model: raising the albedo from 0.3 to 0.4, or returning greenhouse gases to the pre-industrial level?
