Carbon dioxide levels in the atmosphere soared to record highs in 2024, according to the World Meteorological Organization (WMO), locking the planet into further long-term warming and raising concerns over the weakening capacity of natural carbon sinks.
Carbon dioxide in the atmosphere in 2024
The World Meteorological Organization (WMO) has released its annual Greenhouse Gas Bulletin, providing authoritative scientific data ahead of the United Nations Climate Change Conference scheduled for November. The goal of COP30, to be held in Belém, Brazil, is to intensify global climate action.
According to the report, the continued emissions of CO2 from human activities, combined with a surge in wildfires, are the main factors behind the rise in atmospheric carbon dioxide. Another concern is the declining absorption capacity of natural carbon sinks, such as forests and oceans. Together, these dynamics risk creating a dangerous climate feedback loop.
The report shows that the growth rate of carbon dioxide in the atmosphere has tripled since the 1960s, from an annual increase of 0.8 ppm to 2.4 ppm in the decade from 2011 to 2020. Between 2023 and 2024, the global average concentration rose by 3.5 ppm, marking the largest annual increase since modern measurements began in 1957.
Higher carbon dioxide levels due to weaker carbon sinks
When the WMO first published its Greenhouse Gas Bulletin in 2004, the average annual CO2 concentration measured by the Global Atmosphere Watch network was 377.1 ppm. In 2024, it reached 423.9 ppm. Nearly half of all CO2 emitted each year remains in the atmosphere, while the rest is absorbed by terrestrial and oceanic ecosystems.
However, this storage capacity is not constant. As global temperatures rise, oceans absorb less CO2, while land-based sinks face challenges such as prolonged droughts. The record growth between 2023 and 2024 can be attributed mainly to wildfire-related emissions and reduced CO2 uptake by ecosystems, during what became the hottest year ever recorded.
During El Niño years, such as 2024, CO2 levels tend to climb because drier vegetation and widespread wildfires reduce the effectiveness of terrestrial carbon sinks. Severe drought and fires in the Amazon and southern Africa further exacerbated the situation throughout 2024.
Methane and nitrous oxide also reach record levels
Methane accounts for nearly 16% of the long-term greenhouse effect and remains in the atmosphere for about nine years. Around 40% of methane emissions come from natural sources such as wetlands, which are also climate-sensitive, while about 60% stem from human activities including livestock farming, rice cultivation, fossil fuel extraction, landfills, and biomass burning.
In addition to carbon dioxide, both methane and nitrous oxide reached record concentrations in 2024, at 1,942 ppb and 338.0 ppb respectively. Methane levels have increased by 166% and nitrous oxide by 25% compared with pre-industrial levels.
Scientists call for stronger monitoring
The WMO report emphasizes the urgent need to strengthen greenhouse gas monitoring. Report coordinator Oksana Tarasova expressed concern over the declining efficiency of natural carbon sinks: “There is growing concern that land and ocean carbon sinks are becoming less effective, which will increase the amount of CO2 remaining in the atmosphere and accelerate global warming. Continuous and enhanced greenhouse gas monitoring is crucial to understand these cycles.”
Read the full WMO Greenhouse Gas Bulletin here.
