Carbon dioxide levels in the atmosphere jumped by a record amount in 2024, reaching the highest concentration ever measured and locking the planet into more long-term warming, the UN weather agency warned on Wednesday.
The World Meteorological Organisation (WMO) said the rise was fuelled by human-caused emissions, massive wildfires and a drop in the ability of forests and oceans to absorb carbon – a feedback loop that scientists fear could make climate change spiral faster.
From 2023 to 2024, the global average concentration of carbon dioxide surged by 3.5 parts per million (ppm), the biggest increase since records began in 1957.
The annual growth rate has now tripled since the 1960s, climbing from 0.8ppm per year to 2.4ppm per year between 2011 and 2020.
“The heat trapped by CO2 and other greenhouse gases is turbo-charging our climate and leading to more extreme weather,” WMO Deputy Secretary-General Ko Barrett said in a statement.
“Reducing emissions is therefore essential not just for our climate but also for our economic security and community well-being.”
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Storage systems weakening
Average carbon dioxide levels reached 423.9ppm in 2024, compared to 377.1ppm when the WMO first began issuing its annual greenhouse gas bulletin in 2004.
About half of all CO2 released each year stays in the atmosphere, while the rest is absorbed by land ecosystems and oceans.
But that balance is shifting. Hotter oceans hold less gas, and drought and fires are reducing forests’ capacity to store carbon. The effect was especially strong in 2024, the hottest year ever recorded, as a powerful El Niño caused extreme drought and wildfires in the Amazon and southern Africa.
“There is concern that terrestrial and ocean CO2 sinks are becoming less effective, which will increase the amount of CO2 that stays in the atmosphere, thereby accelerating global warming,” Oksana Tarasova, a WMO senior scientific officer, said.
“Sustained and strengthened greenhouse gas monitoring is critical to understanding these loops.”
The likely reason for the record rise between 2023 and 2024 was the combination of wildfire emissions and reduced CO2 uptake by land and sea. Warmer ocean waters are less able to dissolve carbon dioxide, while dry vegetation and fire damage further limit natural absorption.
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Record highs
Methane and nitrous oxide – the second and third most important greenhouse gases linked to human activities – also hit record highs in 2024.
Methane levels climbed to 1,942 parts per billion, up 166 percent from pre-industrial times. About 60 percent comes from human sources such as cattle farming, rice cultivation, fossil fuel extraction and landfills, while the rest comes from natural sources like wetlands. Methane accounts for roughly 16 percent of the warming effect from long-lived greenhouse gases.
Nitrous oxide, mostly produced through fertiliser use and industrial processes, reached 338 parts per billion – a 25 percent rise above pre-industrial levels.
The WMO released its findings ahead of the UN Climate Change Conference in Belém, Brazil, in November, where governments are expected to seek stronger commitments on emissions.
Today’s carbon dioxide emissions will continue to heat the planet for centuries, the agency warned, underscoring the need for urgent action to cut greenhouse gases.
