Test whether the temperature response to greenhouse gases is linear
Three steps, the way the exam actually works: work through the lab, write down your own measurements, then answer a 7-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
- A relationship is linear if equal steps in the input always produce equal steps in the output. If you add the same amount of greenhouse gas five times over, would you expect the same temperature rise each time?
- The model balances absorbed sunlight against emitted infrared, and emission goes as T⁴. Does a fourth power make it easier or harder for the planet to shed extra energy as it warms?
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 at GHG 0 | K |
|---|---|
| Surface temperature at GHG 20 | K |
| Surface temperature at GHG 40 | K |
| Surface temperature at GHG 60 | K |
| Surface temperature at GHG 80 | K |
| Surface temperature at GHG 100 | K |
| Temperature change over the first step, 0 → 20 | K |
| Temperature change over the last step, 80 → 100 | K |
Answer the free response
You have measured the surface temperature of a one-layer energy-balance model at six equally spaced settings of atmospheric greenhouse absorptivity. (a) Using your first and last step sizes, state whether the temperature response to this model's greenhouse control is linear, and support the claim with both numbers. (b) Identify the term in the model that produces the behavior you found, and explain in words why it does. (c) A classmate concludes from your data that "each additional ton of carbon dioxide we emit warms the planet more than the last one did." Evaluate that conclusion, and be explicit about what the slider in this lab does and does not represent. (d) Describe one consequence for climate policy of a system in which the response to a forcing is not proportional to the forcing.
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