Atmospheric CO2 concentrations from the Mauna Loa observatory from 1960 to 2020 are plotted. Annual oscillations are visible against a long-term rising trend.
The long-term increase is best attributed to:
- A
Decreased solar irradiance.
- B
Volcanic eruptions only.
- C
Increased respiration by tropical plants.
- Dcheck_circle
Combustion of fossil fuels and deforestation.
Explanation
Anthropogenic combustion adds CO2 to the atmosphere faster than sinks remove it, producing the secular rise overlaid on seasonal oscillations.