Global carbon dioxide (CO₂) concentration in the atmosphere reached record levels in 2024 due to a combination of wildfires and weakening carbon sinks, according to the latest report by the World Meteorological Organization (WMO) released on Wednesday.

The rise in CO₂ will intensify the impact of temperature increases, including by worsening extreme weather events.

“The heat trapped by CO₂ and other greenhouse gases is turbo-charging our climate and leading to more extreme weather. Reducing emissions is therefore essential not just for our climate but also for our economic security and community well-being,” said WMO Deputy Secretary-General Ko Barrett.

CO₂  levels have tripled since the 1960s, accelerating from an annual average increase of 0.8 ppm per year to 2.4 ppm per year in the decade from 2011 to 2020, according to the report in WMO’s Greenhouse Gas Bulletin.

From 2023 to 2024, the global average concentration of CO₂ surged by 3.5 ppm, the largest increase since modern measurements started in 1957.

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

The report also revealed that the concentrations of methane and nitrous oxide – the second and third most significant long-lived greenhouse gases related to human activities – have also risen to record levels.

“Sustaining and expanding greenhouse gas monitoring are critical to support such efforts,” said Oksana Tarasova, coordinator of the Greenhouse Gas Bulletin, which is one of WMO’s flagship scientific reports and is now in its 21st issue.

The annual report provides an update ahead of this year’s UN Climate Change conference COP30 scheduled for November in Belém, Brazil. Global stakeholders will once again convene to try to ramp up support for climate action.

The WMO data comes a few days after a report found that the Earth is crossing the planetary boundaries that keep life stable and healthy.

Warm-water coral reefs are under unprecedented attack due to warming oceans, the Amazon rainforest is very close to its tipping point as well. Once these points are crossed, the damage will be hard to contain and possibly irreversible, according to researchers from the University of Exeter and the PIK – Potsdam Institute for Climate Impact Research.

CO2 emissions rise, but carbon sinks weaken

The likely reasons for the record growth between 2023 and 2024 are wildfire emissions and a reduced uptake of CO₂  by land and the ocean in 2024, the warmest year on record, with a strong El Niño.

Carbon sinks such as land ecosystems and the ocean usually absorb about half of the CO₂ released. As the temperature rises, the oceans absorb less CO₂  because of decreased solubility at higher temperatures. The land sinks are also impacted in a number of ways, including the potential for more persistent drought.

During El Niño years, CO₂  levels tend to rise because the efficiency of land carbon sinks is reduced by drier vegetation and forest fires – as was the case with exceptional drought and fires in the Amazon and southern Africa in 2024.

“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. Sustained and strengthened greenhouse gas monitoring is critical to understanding these loops,” said Oksana Tarasova, a WMO senior scientific officer.

A portion of the CO₂ released today is likely to remain in the atmosphere for hundreds of years, and will continue to impact the global climate for a long time.

Concentration of other gases is rising as well

Methane accounts for about 16% of the warming effect on our climate and stays in the atmosphere for about nine years. This also makes it a low-hanging fruit when it comes to climate action.

The globally averaged methane concentration in 2024 was 1,942 parts per billion (ppb),  an increase of 166% above pre-industrial (pre-1750) levels.

Around 40% of methane is emitted into the atmosphere by natural sources, such as wetlands, which are sensitive to climate as well. The other 60% comes from anthropogenic sources such as cattle, rice farming, fossil fuel, landfills and biomass burning.

The third most important long-lived greenhouse gas, nitrous oxide, that stays in the atmosphere for around a century, reached 338.0 ppb in 2024, an increase of 25% over the pre-industrial level. This gas comes from both natural sources and human activities such as biomass burning, fertilizer use and various industrial processes.

WMO said that countries need to continue to strengthen the monitoring of CO₂ levels to inform policy action. In addition, it emphasized the need to preserve existing carbon sinks.

Image Credits: WMO.