The amount of CO2 in the atmosphere increased by a record amount in 2024, potentially further warming the planet and leading to more extreme climate events. The concentration of greenhouse gases in the air increased by 3.5 ppm (parts per million) between 2023 and 2024 – the highest increase since modern measurements began in 1957.
This is stated in the World Meteorological Organization’s (WMO) annual Greenhouse Gas Bulletin, published ahead of next month’s United Nations Climate Change Conference in Brazil. The WMO also notes that CO₂ levels are now the highest in 800,000 years (and possibly beyond) based on paleoclimate records.
Human activities
Climate experts point to the continued rise in CO2 emissions caused by human activity. Previous research has shown that these emissions also reached a record high in 2024. At the same time, the WMO notes that the oceans’ and land’s capacity to absorb CO2 is declining.
Usually, about half of the CO2 emitted ends up in the atmosphere, while natural carbon sinks, such as oceans and forests, absorb the other half. However, rising temperatures are reducing the ocean’s ability to store CO2. Drought, in turn, is putting pressure on the land’s storage capacity.
Heat records
WMO confirms 2024 was the warmest year on record, with a global mean surface temperature anomaly of 1.55 °C ± 0.13 °C above the 1850-1900 baseline (pre-industrial reference). That likely makes 2024 the first calendar year with global average warming above 1.5 °C.
The elevated greenhouse gas levels, in turn, contributed to intensifying impacts: glacier and sea ice loss, accelerating sea level rise, and exacerbating extremes (droughts, floods, heatwaves).
Vicious circle
“There are concerns that carbon sinks on land and in the sea will become less effective, leaving more CO2 in the atmosphere and accelerating global warming,” warns Oksana Tarasova, coordinator of the report at the WMO. Therefore, scientists fear a vicious cycle in which increasing global warming will further reduce the effectiveness of natural carbon sinks, accelerating global warming.
CO2 is the primary heat-trapping gas in the atmosphere. It accumulates in the atmosphere and has a very long lifetime… Every single molecule emitted into the atmosphere will have a global impact.
Increased risks
Concentrations of other important greenhouse gases, methane and nitrous oxide, also rose to record levels, increasing by 16% and 25%, respectively, against pre-industrial levels, while CO2 rose by 52%.
The next few years will likely test the resilience of the 1.5 °C target of the Paris Agreement — surpassing it in a given year does not immediately mean failure of the long-term goal. Still, it significantly increases risks and narrows margins.
