Which of the following processes help to regulate carbon dioxide levels on human timescales:

Question

BlackTom AI · Accepted Answer

To tackle the question, I’ll evaluate each option in turn and explain why it does or does not regulate atmospheric CO2 on human timescales.

Option a: Rising ocean carbonate compensation depth. The carbonate compensation depth (CCD) is a long-term oceanic balance that shifts over thousands to millions of years as carbonate sediments accumulate or dissolve. Changes here operate on geological timescales, not on the rapid, human-relevant timescale. Therefore, CCD rise is not a primary regulator of CO2 on human timescales.

Option b: Vegetation expansion. When land vegetation increases, photosynthesis draws CO2 from the atmosphere, and plant growth stores carbon in biomass and soils. This process can respond on much shorter, human-relevant timescales (years to decades), making it a direct regulator of atmospheric CO2 over those timescales. It also can be enhanced by land-use changes and reforestation, providing a relatively rapid mechanism to draw down CO2.

Option c: Ocean warming. Warmer ocean waters decrease the solubility of CO2 in seawater, which tends to reduce the ocean’s capacity to absorb CO2 from the atmosphere. While ocean warming is linked to the carbon cycle, it does not actively remove CO2 on short timescales; in fact, it can impede CO2 uptake. Thus, it is not a regulation mechanism that lowers atmospheric CO2 on human timescales.

Option d: Increased silicate rock weathering. Weathering of silicate rocks does draw down atmospheric CO2, but the weathering feedback operates over longer, geologic timescales (thousands to millions of years). While it is a crucial long-term sink, its regulation of CO2 is too slow to be considered a primary regulator on human timescales.

Putting these together, vegetation expansion stands out as the mechanism that can adjust atmospheric CO2 rapidly enough to be relevant in the near term, whereas the others function predominantly on much longer timescales or have opposing effects on CO2 uptake.

GEOL0076_25-26 End Of Term Quiz - 60 minutes

Which of the following processes help to regulate carbon dioxide levels on human timescales:

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