GLY1073 — Coupled Carbon Cycle and Population Model

1.) IPCC Scenario B assumes that anthropogenic CO₂ emissions (i.e., fossil fuel emissions and deforestation emissions) are held at current rates (5 Gtons C/yr and 2 Gtons/yr for fossil fuels and deforestation, respectively). This is equivalent to the model you did last week so you do not need to do anything to your carbon cycle model.

a.) What is the predicted concentration of atmospheric CO₂ in 2100?

b.) How does it compare with IPCC estimates?

2.) IPCC Scenario C assumes a 50% reduction in anthropogenic CO₂ emissions by the middle of the next century. Use the graphical input functions to simulate a steady decline to 50% emissions over the next century.

a.) What is the predicted atmospheric CO₂ concentration in 2100?

b.) How does it compare with IPCC estimates?

3.) IPCC Scenario A - Business as Usual. Create a new model which couples the carbon cycle and the population/fossil fuels model. The fossil fuel flux in the carbon cycle is equal to the sum of carbon produced by oil, gas, and coal consumption. Deforestation should become a function of the changing human population by assuming a per capita carbon input of 2Gt/6 billion people. Be sure that the resevoirs and fluxes in your carbon cycle model reflect present-day values and don’t forget to convert carbon units to Gtons (i.e., one joule of energy produces 1.69E-20 Gtons C).

a.) What is the concentration (ppm) of atmospheric CO₂ at the end of the next century (2100).

b.)How does this compare with the "Business As Usual" prediction of the Intergovernmental Panel on Climate Change (IPCC) shown below (read IPCC# for 2100 off of the graph below)?

c.) How does your predicted atmospheric CO₂ concentration compare with the pre-Industrial concentration you simulated last week?

4.) Given the descriptions of the IPCC 1990 Scenarios below, which scenario do you think is most realistic (probable)? Why?

IPCC 1990 Scenarios

The Intergovernmental Panel on Climate Change considers four different policy scenarios from which emissions of greenhouse gases can be determined.

The first, scenario A (or sometimes it is called the BaU (Business as Usual) scenario) assumes that nations continue to follow present practices of using coal and natural gas as main sources of energy for power production, that automobiles continue to be manufactured without any significant increase in efficiency, carbon monoxide controls are modest, deforestation continues until tropical forests are depleted, and agricultural emissions of methane and nitrous oxide are not controlled. This scenario acknowledges that CFC emissions will be partially reduced as a result of the Montreal Protocol.

Scenario B has reduced emissions, particularly in the long run. It assumes that the energy use moves toward more lower carbon fuels, notably natural gas. Burning natural gas gives carbon dioxide and water vapor as byproducts, but a lower amount of carbon dioxide is released per unit energy produced compared to coal. This scenario assumes that stringent carbon monoxide controls are implemented, deforestation is reversed, and the Montreal Protocol is implemented with full participation.

Scenario C produces a more significant reduction in greenhouse emissions, but at a cost of more significant change in societal behavior. Energy policy requires a shift toward renewables and nuclear energy in the second half of the next century. CFCs would be phased out and agricultural emissions are limited.