In 2018 average atmospheric CO2 concentrations reached 408ppm.
Average annual atmospheric C02 concentrations: NOAA1
In 1750 atmospheric CO2 concentrations were about 278ppm2. Atmospheric CO2 concentrations have been increasing since the Industrial Revolution. The last time atmospheric CO2 concentrations were similar to today was 3 million years ago, when the global average temperature was 3°C higher, and sea levels were around 25m higher 3.
Atmospheric CO2 concentrations are currently increasing by about 2ppm per year4.
- NOAA, ‘ESRL Global Monitoring Division: Global Greenhouse Gas Reference Network – Trends in Atmospheric Carbon Dioxide’ (National Oceanic & Atmospheric Administration, 2019) https://www.esrl.noaa.gov/gmd/ccgg/trends/data.html [accessed 20 December 2019]
- Dlugokencky, E, ‘Atmospheric Composition: Long-Lived Greenhouse Gases’, State of the Climate in 2017 (Special Supplement): Bulletin of the American Meteorological Society, 99.8 (2018), S46-S49. Link
- Wuebbles, D. et al. ‘Our Globally Changing Climate’, in Climate Science Special Report: Fourth National Climate Assessment, Volume I, ed. by D Wuebbles et al. (Washington DC: US Global Change Research Program, 2017) p.53 https://doi.org/10.7930/J08S4N35
- IPCC, Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Geneva: Intergovernmental Panel on Climate Change, 2014) p.44. Link.