Carbon dioxide levels in the atmosphere reached a record in 2024, committing the planet to more long-term temperature increase, according to a new report from the World Meteorological Organization (WMO).

The WMO Greenhouse Gas Bulletin said continued emissions of CO2 from human activities and an upsurge from wildfires were responsible, as well as reduced CO2 absorption by ‘sinks’ such as land ecosystems and the ocean in what threatens to be a vicious climate cycle.

When the bulletin was first published in 2004, the annual average level of CO2 measured by WMO’s Global Atmosphere Watch network of monitoring stations was 377.1 ppm. In 2024 it was 423.9 ppm.

About half of the total CO2 emitted each year remains in the atmosphere and the rest is absorbed by Earth’s land ecosystems and oceans. However, this storage is not permanent. As global temperature rises, the oceans absorb less CO2 because of decreased solubility at higher temperatures, whilst land sinks are impacted on a number of ways, including the potential for more persistent drought.

Concentrations of methane and nitrous oxide – the second and third most important long-lived greenhouse gases related to human activities – have also risen to record levels.

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