Labs / Geography
Planetary Energy Balance
A planet warms until the energy it radiates away exactly matches the sunlight it soaks up. Slide the sunlight, the reflectivity, and the greenhouse-gas amount — or drag on the sky to add gases — and watch the temperature hunt for the point where the incoming and outgoing arrows balance.
in 238 W/m²out 238 W/m²net +0.0 W/m²T 15.0 °C≈ balanced
What to try
- Push the greenhouse-gas slider up. Why does the surface keep warming even though the sunlight coming in never changed?
- Start from “Earth today” and slowly raise the albedo. Is there a point where a tiny nudge suddenly tips the whole planet into a frozen snowball?
- Once ice starts forming, notice the albedo climbing on its own. How does reflecting more sunlight make the planet even colder — a feedback that feeds itself?
- Try the “Faint young Sun” scenario. What would it take — more gases or less ice — to keep an early Earth from freezing solid?
- Can you find two very different greenhouse and albedo settings that land on the same surface temperature? What does that tell you about balance versus cause?