Card #11: Concentration of CO2
About half of CO2 emissions are captured by natural carbon sinks. The other half remains in the atmosphere. The concentration of CO2 in the air has increased from 280 to 415 ppm (parts per million) over the past 150 years. This is higher than at any point over the last three million years.
CO2 measurements have been taken since 1958 in Hawaii, on Big Island, on the flanks of the Mauna Loa volcano. They were initiated by Charles Keeling. In the blue scenario (2°C) they increase until 2040-2050, then they decrease because emissions will have been reduced so much that natural sinks no longer absorb them.
To go further
The surplus CO2 is permanently stored in the atmosphere (no chemical degradation process). There are only 2 physical processes: dissolution of CO2 in the oceans, and synthesis of CO2 via photosynthesis (in the presence of photons).
- in 100 years' time, 40% of the surplus CO2 released today will still remain in the atmosphere
- in 1000 years' time, 20% of the surplus CO2 emitted today will still remain in the atmosphere
- in 10,000 years' time, 10% of the surplus CO2 emitted today will still remain in the atmosphere.
It is an almost irreversible process.
French emission factors
In France, the main cause of CO2 emissions has shifted from industry to transportation in 150 years.