Carbon-dioxide emissions from human activities and wildfires rose by an unprecedented amount last year, while the land and oceans' ability to absorb carbon diminished, according to the World Meteorological Organization.

The global average concentration of CO2 in the atmosphere surged by 3.5 parts per million from 2023 and 2024, the United Nations agency said in its annual Greenhouse Gas Bulletin on Wednesday. That represents the largest yearly increase since modern measurements started in 1957 and is above the average increase of 2.4ppm in the decade 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.”

The greenhouse gases accumulated in the atmosphere are warming the planet, unleashing extreme weather events that have caused thousands of deaths and billions in economic losses annually. Last year, global temperatures rose above 1.5C on an annual basis for the first time ever, breaching a threshold set by global leaders when they signed the Paris Agreement a decade ago.

Concentrations of methane and nitrous oxide - the second and third most potent greenhouse gases related to human activities - also increased to record levels in 2024, the WMO said.

Methane concentrations were up 166% compared with pre-industrial times in 2024.

About half of the carbon emitted by human activities every year remains in the atmosphere and the rest is absorbed by Earth's ecosystems. But as temperatures increase, the ability of ocean and land to absorb CO2 decreases. The likely reasons for the record CO2 increase last year was wildfire emissions, reduced uptake of CO2 by carbon sinks, and a strong El Niño.

“There is concern that terrestrial and ocean CO2 sinks are becoming less effective,” said Oksana Tarasova, a WMO senior scientific officer. That“will increase the amount of CO2 that stays in the atmosphere, thereby accelerating global warming.”

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