Question

Explain why atmospheric concentrations of carbon dioxide are expected to increase in the future.

Answer 1

Atmospheric CO2 is expected to rise in the future mainly because human emissions of CO2 continue to exceed the rate at which natural processes remove it. The key reasons:

- Ongoing anthropogenic emissions
- Burning of fossil fuels (coal, oil, natural gas) for electricity, industry, transport and heating releases large amounts of CO2.
- Industrial processes (e.g., cement manufacture) and some agricultural practices also emit CO2.
- Continued population and economic growth — especially in developing regions — tends to raise energy demand and fossil-fuel use unless replaced by low‑carbon energy.

- Loss or weakening of natural sinks
- Deforestation and land‑use change both release stored carbon and reduce the capacity of vegetation to absorb CO2.
- Warming reduces how much CO2 the oceans can hold (warmer water dissolves less CO2) and can weaken biological uptake (phytoplankton, forests), lowering net sink strength.

- Positive climate feedbacks
- Thawing permafrost and drying soils can release stored organic carbon as CO2 (and methane), adding to atmospheric CO2.
- These feedbacks amplify warming and further reduce net removal of CO2.

- Long atmospheric lifetime and cumulative effect
- A large fraction of emitted CO2 remains in the atmosphere for decades to centuries, so atmospheric concentrations reflect cumulative emissions. Even if emissions slow, concentrations can keep rising until removals match emissions.

Because expected future human emissions (unless sharply reduced) combined with weaker sinks and positive feedbacks will continue to outpace natural removal, atmospheric CO2 concentrations are projected to increase.