Measure the greenhouse effect and the albedo feedback
Three steps, the way the exam actually works: work through the lab, write down your own measurements, then answer a 6-point free response. What you recorded goes to the grader with your writing, so a conclusion that does not follow from your own numbers will cost you the point — exactly as it would with a real reader.
Predict before you look
- Energy balance requires absorbed sunlight to equal emitted infrared. If a planet reflects more sunlight away, must it end up emitting more or less to stay in balance?
- The Stefan–Boltzmann law makes emitted power proportional to T⁴. Does a fourth power make temperature MORE or LESS sensitive to a change in absorbed energy than a linear relationship would?
Nothing to submit here — these are to think through, so the prediction below is an informed one rather than a guess.
Commit to an answer now. It is not graded and being wrong costs nothing — the point is to have something specific to reconcile against once you have the data.
Answer every prediction to unlock the lab. A sentence is enough.
Run the investigation
Predictions first
The procedure and the simulation unlock once you have committed above. Observing before predicting is how a wrong intuition survives a lab intact.
Record what you measured
These are your numbers, not ours. The grader sees them, so your conclusions have to follow from what you actually recorded.
| Surface temperature with no greenhouse gases (albedo 0.30) | K |
|---|---|
| Surface temperature at GHG 78 (albedo 0.30) | K |
| Greenhouse boost the lab reports | K |
| Surface temperature at albedo 0.60 (GHG 78) | K |
| Surface temperature at albedo 0.10 (GHG 78) | K |
Answer the free response
This is a simple energy-balance model of Earth. (a) Using your first two temperature readings, state the size of the greenhouse effect in kelvins and describe the mechanism by which greenhouse gases raise the surface temperature. Be specific about the type of radiation involved. (b) Using your two albedo readings, state the relationship between albedo and surface temperature, and explain it in terms of the energy entering the Earth system. (c) Explain why the difference you measured in part (a) matters for life on Earth, referring to the temperature you recorded without greenhouse gases. (d) Describe the ice–albedo feedback loop, using your albedo data to support each step, and identify whether it is a positive or a negative feedback.
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