Balancing the Global Carbon Budget

Part 1: Engage

The Keeling Curve is one of the most famous graphs in science. It shows that the amount of carbon dioxide (CO2) in Earth’s atmosphere has been rising steadily since 1958.

The Puzzling Question: Earth has two massive “sinks” that absorb CO2: the oceans (hydrosphere) and global forests (biosphere). If these sinks are so large, why is the atmospheric CO2 still rising? Why can’t they “keep up”?

Write your initial hypothesis:

Part 2: Explore

Open the Global Carbon Cycle Simulation.

Investigation A: The Natural Balance (Pre-Industrial)

  1. Set all human activity sliders (Fossil Fuel Combustion, Deforestation) to 0.
  2. Click Run Simulation. Observe the “Atmospheric Carbon” graph.
    • Is the level of carbon rising, falling, or stable?
  3. Observe the arrows (fluxes) between the Atmosphere and the Biosphere.
    • What process is represented by the arrow moving FROM the Atmosphere TO the Biosphere?
    • What process is represented by the arrow moving FROM the Biosphere TO the Atmosphere?
  4. Compare the magnitudes (thickness) of these two arrows. How do they relate to the stability of the atmospheric carbon?

Investigation B: The Human Impact

  1. Reset the simulation.
  2. Increase Fossil Fuel Combustion to a moderate level.
  3. Observe the “Carbon Reservoirs” data table.
    • Which reservoir is losing carbon? ______
    • Which reservoirs are gaining carbon? ______
  4. Increase Ocean Absorption Efficiency. Does this stop the rise in atmospheric CO2?

Part 3: Explain

  1. Analyze Fluxes: Explain how “Cellular Respiration” and “Photosynthesis” create a cycle between the atmosphere and the biosphere.
  2. Define a “Sink”: Based on your simulation data, what is the role of the Geosphere in the long-term carbon cycle? Why is “Fossil Fuel Combustion” considered a “short-circuit” in this cycle?
  3. Equilibrium: Even when the Ocean pulls more carbon out of the air, why does the atmospheric CO2 continue to climb? Use the concept of “Rates of Transfer” in your explanation.

Part 4: Elaborate & Evaluate

The Management Challenge: You are a climate policy advisor. A group proposes planting 1 trillion trees to “solve” climate change.

Using the simulation, test this solution:

  1. Set Fossil Fuel Combustion to high.
  2. Set Reforestation Rate to maximum.
  3. Observe the long-term trend (100+ years).

Construct an Evidence-Based Argument: Can reforestation alone return the atmosphere to pre-industrial levels while we continue to burn fossil fuels? Use evidence from the “Biosphere Carbon” vs “Atmospheric Carbon” graphs to support your claim.

(Space for scientific argument)