Question

which conclusion about the stability of the carbon cycle can be drawn from the data shown in the graph below? carbon dioxide concentration at mauna loa observatory
a. the cycle is currently in a stable state because the yearly fluctuation between maximum and minimum co2 levels is decreasing over time.

b. the cycle is highly stable, as evidenced by the large annual decrease in co2 levels each fall due to seasonal oceanic upwelling.

c. the cycle’s stability is declining because the overall trend shows a continuous, significant increase in atmospheric co2 concentration.

d. the cycle is balanced, indicated by the fact that the majority of co2 emissions are absorbed equally between the terrestrial biosphere and the oceans

Explanation:

• Option A: The graph shows yearly fluctuations (the zig - zag) but the overall trend is upward. Also, the yearly fluctuation between max and min CO₂ levels is not decreasing; if anything, as the overall CO₂ increases, the amplitude of the yearly fluctuations might be increasing or at least not decreasing. So A is wrong.
• Option B: The large annual decrease in CO₂ levels each fall is part of the natural yearly cycle (the zig - zag), but the overall trend of increasing CO₂ shows that the cycle is not highly stable. Also, the reason for the fall decrease is mainly plant respiration/photosynthesis (not oceanic upwelling as a primary cause for the fall decrease). So B is wrong.
• Option C: The graph shows a continuous, significant increase in atmospheric CO₂ concentration over time. A stable carbon cycle would have relatively constant CO₂ levels over long - term. The upward trend means the cycle's ability to maintain a stable CO₂ level (its stability) is declining. This makes sense.
• Option D: The graph does not show anything about CO₂ emissions being absorbed equally between the terrestrial biosphere and the oceans. The graph only shows atmospheric CO₂ concentration over time. So D is wrong.

Answer:

C. The cycle's stability is declining because the overall trend shows a continuous, significant increase in atmospheric CO₂ concentration.