Page Updated: Tuesday, September 30, 2025 11:20 AM ET

Guardian UK - Environment

The most important number of the climate crisis: 425.2 - atmospheric CO - 2 - in parts per million, 21 July 2024 - 75.2 - above safe level - 27.1 - in past 10 years - 280 - 300 - 320 - 340 - 360 - 380 - 400 - 420 parts per million - 1960 - 1990 - 2014 - 2024 - Safe level: 350ppm - Latest: 425.2ppm - 280 - 300 - 320 - 340 - 360 - 380 - 400 - 420 parts per million - 1960 - 1990 - 2014 - 2024 - Safe level: 350ppm - Latest: 425.2ppm - Source: NOAA. Chart baseline is 280ppm - the preindustrial average. Safe level a stabilisation scenario set out by IPCC. Daily average CO2 value at Mauna Loa.

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