The global average concentration of CO2 surged by 3.5 parts per million to reach 423.9 ppm last year, fuelling worries that the planet’s ability to soak up excess carbon is weakening
15 October 2025
Between 2023 and 2024, the global average concentration of CO2 surged by 3.5 parts per million (ppm) to reach 423.9 ppm, the WMO has said. This is the largest increase since modern measurements started in 1957 and is well in excess of the 2022 to 2023 increase of 2.3 ppm.