According to the WMO Greenhouse Gas Bulletin released this October, carbon dioxide (CO₂) levels from 2023 to 2024 had the biggest one-year rise since records began in 1957. What factors contributed to this record rise?
- First of all, globally the fossil fuel emissions have not gone down in 2024, despite all promises in the 2015 Paris climate treaty. There are no signs for the emissions to go down any time soon. The fossil fuel emissions are the major cause of the CO₂ increase in the atmosphere and the cause of global warming.
The results includes data from ICOS stations, including several stations from the ICOS-Sweden network operated by Lund University. How do the stations help us better understand what’s happening in the atmosphere?
- On average half of the extra CO₂ we emit is absorbed by ocean and the land, otherwise the CO₂ growth rate would be about 5 ppm/year with current emissions. Now it is on average 2.5 ppm/year, but in 2024 we saw 3.5 ppm/year. As fossil fuel emissions stayed constant, the absorption must have decreased, so either land or ocean or both have taken up less CO₂. This could be due to more fires caused by severe droughts, less uptake by vegetation due to heat stress or floods, less uptake of the ocean by increased sea surface temperature and pH (feedback from increased CO₂) and/or changing circulation patterns. All of these are possible feedbacks from climate change caused by the same CO₂. Only observations can help us explain what are the contributing factors that explain the changes.
In the key messages, you highlight growing concerns about carbon sinks such as forests and oceans. What uncertainties do we face about how these natural sinks will behave in the coming years, and why does that matter for meeting climate goals?
- If we keep emissions high, and CO₂ keeps rising, warming will increase and we risk that these feedbacks further accelerate global warming, possibly to the point that CO₂ emission reduction will need to accelerate even further or that we need to store even more CO₂ using expensive technologies like CCS, CDR and more, to allow for remaining emissions where we have no alternative for fossil fuels.
The bulletin is released before the COP climate meetings and gets worldwide attention. What message do you hope policymakers and the public take away from this year’s results?
- That there is no time to waste any more. We are like the driver that is driving the family car at maximum speed into a concrete wall with the foot on the gas pedal pushed to the floor, with just 50 meters to go until the wall. We need to take the foot off and brake to the max now. We can fully realize this now since at least 1990 and hardly any action has been taken since then, emissions have just kept on increasing. We waited 35 years and now there are only a few years left to keep global warming within 2 degrees, which will already cause big disruptions and require an expensive adaptation that will harm especially the Global South, but also affect rich nations like those in Europe. If we go on like this global warming will go to 4 degrees or more, which equals 8 degrees on land, for example here in Southern Sweden, and up to even double that in the arctic regions.
Read the WMO Greenhouse Gas Bulletin (published 16 October, 2025)
The ICOS Carbon Portal
Emission Gap report 2025 (UNEP)