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.
Run the investigation
- 1Set the albedo to 0.30, then drag the greenhouse-gas slider all the way down to 0 and record the surface temperature.
- 2Raise the greenhouse-gas slider to 78 and record both the surface temperature and the greenhouse boost the lab reports.
- 3Leaving the greenhouse-gas slider at 78, raise the albedo to 0.60 and record the surface temperature.
- 4Now lower the albedo to 0.10 and record the surface temperature one more time.
Booting the lab…
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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