Greenhouse Effect: Modeling Earth’s Energy Budget

Part 1: Engage (Anchoring Phenomenon)

Venus and Earth are nearly the same size and distance from the Sun — yet Venus has a scorching surface temperature of 462°C, while Earth averages a livable 15°C. What makes these two planets so different? Venus’s atmosphere is 96.5% carbon dioxide (CO₂) — about 96,500 ppm — compared to Earth’s current ~420 ppm. Could the composition of their atmospheres explain the dramatic temperature difference?

1. Observations and Questions:

• Why is Venus so much hotter than Earth despite being a similar size and distance from the Sun?
• What role might greenhouse gases like CO₂ play in determining a planet’s surface temperature?
• Generate at least two “need to know” questions about how greenhouse gases affect Earth’s energy balance.

Part 2: Explore (Simulation Investigation)

Open the [Greenhouse Effect Simulation]. This interactive model lets you control four key variables that influence Earth’s energy budget: Greenhouse Gas Concentration (100–1000 ppm CO₂ eq), Surface Albedo (5–80%), Solar Intensity (80–120%), and Cloud Cover (0–100%). The simulation includes a temperature graph, a data table with record/export capability, and macro/microscopic visual views.

2. Data Collection:

Investigation A: Establish a Baseline

• Reset the simulation to default values: GHG = 400 ppm, Albedo = 30%, Solar = 100%, Clouds = 50%
• Click Record Current State to log the initial conditions
• Click Play and let the simulation run for ~10 simulated years
• Record the final Global Temperature and the Incoming vs. Outgoing Energy values
• Note: Incoming energy (absorbed solar) ≈ Outgoing energy (OLR) at equilibrium — this is Earth’s balanced energy budget

Investigation B: Effect of Greenhouse Gases

• Reset the simulation. Set GHG to 200 ppm. Record temperature after 10 years
• Repeat at 400, 600, 800, and 1000 ppm (keep all other variables at default)
• Use Record Current State to log each data point to the data table
• In the Microscopic View, observe how red (infrared) photons interact with GHG molecules compared to yellow (solar) photons

Investigation C: Effect of Surface Albedo

• Reset the simulation. Set GHG to 400 ppm and Albedo to 5% (dark ocean-like surface)
• Record temperature after 10 years
• Repeat at 20%, 40%, 60%, and 80% albedo (80% simulates an ice-covered planet)
• Switch between Macroscopic View and Microscopic View to observe how reflected yellow photons change

Investigation D: Effect of Solar Intensity

• Reset the simulation. Test Solar Intensity at 80%, 90%, 100%, 110%, and 120%
• Record temperature and energy values for each setting

Investigation E: Effect of Cloud Cover

• Reset the simulation. Test Cloud Cover at 0%, 25%, 50%, 75%, and 100%
• Record temperature and note any competing effects (clouds both reflect incoming solar AND trap outgoing infrared)

Data Table:

Graph Analysis:

• Use the simulation’s built-in temperature graph to visualize temperature trends over time
• Export your data as CSV using the Export CSV button
• Plot GHG concentration vs. temperature. What shape does the curve have?
• Plot Albedo vs. temperature. How does this compare to the GHG curve?

Part 3: Explain (Sensemaking)

3. Analyzing the Energy Budget:

• Look at your Investigation B data. How does increasing GHG concentration affect Global Temperature? Describe the shape of the relationship — is it linear? Logarithmic? What does this imply about the greenhouse effect at very high concentrations (like Venus levels)?

• From Investigation C, how does changing Surface Albedo affect temperature? Which has a stronger effect on the energy budget — albedo or GHG concentration, based on the magnitude of temperature change you observed?

• In Investigation E, clouds seem to have a dual role. Using your data, explain the competing effects of clouds: they reflect incoming solar radiation (cooling) but also trap outgoing infrared radiation (warming). Which effect dominates in your simulation results?

• Based on the Microscopic View, describe the difference between how yellow (visible light) photons and red (infrared) photons interact with greenhouse gas molecules. Why does this difference matter for Earth’s energy budget?

4. Connecting to the Venus-Earth Phenomenon:

• Venus has a CO₂ concentration of ~96,500 ppm (roughly 230 times Earth’s current level). Based on the shape of your GHG vs. temperature curve, explain why Venus is 462°C while Earth is 15°C.

• Venus also has a very high albedo (~70%) due to its thick cloud layer of sulfuric acid. If Venus’s albedo is higher than Earth’s (~30%), why doesn’t the high albedo cool Venus enough to offset the greenhouse effect?

• Earth has experienced major climate shifts in its history (snowball Earth periods, hothouse climates). Using the variables you investigated, identify which factor(s) could have been different during these periods to produce such dramatic temperature changes.

Part 4: Elaborate / Evaluate (Argumentation & Modeling)

5. Model Construction and Causal Explanation

Your task is to develop a scientific model of Earth’s energy budget that explains how variations in energy flow into and out of Earth’s systems result in changes in climate. Your model must integrate your simulation data with the mechanistic understanding of the greenhouse effect.

Construct a visual model (concept map, flow chart, annotated diagram, or system model) that includes:

• Components: Solar radiation (incoming), reflected radiation (albedo), absorbed surface energy, infrared radiation (outgoing), greenhouse gas molecules (CO₂, H₂O, CH₄), clouds, atmospheric layers, and the surface (ocean/land/ice)

• Relationships: How each variable you tested (GHG, Albedo, Solar Intensity, Cloud Cover) affects the energy budget. Organize these factors into three groups: factors that affect energy INPUT, factors that affect energy OUTPUT, and factors that affect energy STORAGE/redistribution. For each factor, describe whether its effect is causal (directly changes the energy flow) or correlational (associated with a change but mediated by other processes)

• Connections: Provide a mechanistic account of the relationship between energy flow and climate change. Include specific cause-effect relationships such as: how increasing CO₂ reduces outgoing longwave radiation → creates an energy imbalance → Earth warms until a new equilibrium is reached. Address the net effect of competing factors — for example, if solar intensity decreases by 5% but GHG concentration doubles, what happens to the equilibrium temperature?

Write a CER (Claim, Evidence, Reasoning) to accompany your model, answering the driving question: Why is Venus so much hotter than Earth, and how does the greenhouse effect control a planet’s energy budget?

• Claim: A clear, concise answer that explains how differences in atmospheric composition affect planetary energy balance and surface temperature, comparing Venus to Earth

• Evidence: Specific quantitative data from at least three of your simulation investigations (GHG, Albedo, Solar, Clouds). Include temperature values, energy flow comparisons, and descriptions of photon behavior from the Microscopic View. Reference your data table rows

• Reasoning: Explain how the evidence supports your claim by describing:

  • How greenhouse gases selectively interact with infrared radiation but not visible light
  • How changes in GHG concentration shift the energy balance (incoming vs. outgoing)
  • How the logarithmic relationship between GHG concentration and temperature explains the extreme difference between Venus (~96,500 ppm CO₂) and Earth (~420 ppm CO₂)
  • How competing factors (albedo, clouds, solar intensity) could amplify or counteract greenhouse warming
  • How this model explains Earth’s climate sensitivity and the potential consequences of increasing atmospheric CO₂

Teacher Notes & NGSS Alignment

Performance Expectation: HS-ESS2-4. Use a model to describe how variations in the flow of energy into and out of Earth’s systems result in changes in climate.

Alignment to Dimensions:

• SEP: Developing and Using Models — Students develop a visual model of Earth’s energy budget that traces energy flows into and out of the Earth system, using simulation data to describe causal relationships between variables (GHG concentration, albedo, solar intensity, cloud cover) and climate outcomes (temperature change).
• DCI: ESS2.A (Earth Materials and Systems) — Earth’s systems interact over a range of spatial and temporal scales, and changes in atmospheric composition (greenhouse gases) alter the flow of energy through Earth’s climate system.
• DCI: ESS2.D (Weather and Climate) — The role of greenhouse gases in determining Earth’s energy budget and surface temperature; the fundamental relationship between atmospheric CO₂ concentration and planetary temperature.
• DCI: ESS1.B (Earth and the Solar System — secondary) — The similarities and differences among planets (Earth vs. Venus) provide evidence for how atmospheric composition affects planetary climate.
• CCC: Cause and Effect — Students identify causal relationships between specific variables (GHG concentration, albedo, solar intensity, cloud cover) and climate outcomes (temperature change, energy imbalance), and evaluate the net effect of competing causes.

Evidence Statement Mapping:

• 1 (Components): Students develop a model that includes factors affecting energy INPUT (solar intensity), energy OUTPUT (albedo, greenhouse gases, clouds), and energy STORAGE/redistribution (atmospheric absorption, surface emission). Demonstrated in Part 4 when students construct a visual model categorizing factors into input/output/storage groups.
• 2 (Relationships): Students use the model to organize factors into input/output/storage groups and describe whether each relationship is causal or correlational. Demonstrated in Parts 2 and 3 as students collect and analyze data showing how each variable affects temperature and energy flows.
• 3 (Connections): Students provide a mechanistic account of the relationship between energy flow and climate change, identifying specific cause-effect relationships and evaluating the net effect of competing factors. Demonstrated in Part 3 (connecting to Venus-Earth phenomenon) and Part 4 (CER argument and model construction).