Weekly averages
| 22 September 2019: | 408.32 ppm |
| 3 October 2018: | 405.63 ppm |
| 3 October 2009: | 384.73 ppm |
| Pre-industrial base: | 280 |
| Safe level: | 350 |
Atmospheric CO2 reading from Mauna Loa, Hawaii (part per million). Source: NOAA-ESRL
(Source: The Guardian, October 2019)