Greenhouse gas concentrations in the atmosphere hit a record high last year

Carbon dioxide concentrations in the atmosphere reached a record 420 ppm (parts per million) last year, up 2.3 ppm year on year and 151% compared with the pre-industrial era. The relative increase in methane concentrations was even higher. The World Meteorological Organization (WMO) reported the figures, saying they mean the planet is now set to keep warming for many years to come.

According to the WMO, carbon dioxide is accumulating in the atmosphere at the fastest rate in human history, with concentrations rising by 11.4% (42.9 ppm) in the past 20 years alone. The increase in atmospheric CO2 concentrations was higher last year than in 2022, but lower than three years ago. The annual rise of 2.3 ppm also marks the twelfth consecutive year of an increase of at least 2 ppm.

"Another year, another record. This should alarm those making key decisions. We are clearly not on track to meet the Paris Agreement goals of limiting global warming to below 2 °C while also striving to keep it to a maximum of 1.5 °C compared with the pre-industrial era. These are not just statistics. Every part per million and every fraction of a degree of warming has a real impact on our lives and our planet," said WMO Secretary-General Celeste Saulo.

According to the WMO, the continued rise in atmospheric greenhouse gas concentrations is the result of major vegetation fires last year, a likely decline in forests’ ability to absorb CO2 emissions, and persistently high CO2 emissions from burning fossil fuels.

Carbon dioxide is not the only gas whose concentration is rising. The largest relative increase compared with the pre-industrial era (the period before 1750) was recorded for methane, at 265%. Nitrous oxide concentrations rose by 125% over the same period.

The WMO analysis focuses on greenhouse gas concentrations rather than emissions, since less than half of CO2 emissions remain in the atmosphere. Around one quarter is absorbed by the oceans and just under 30% by land ecosystems. These figures can, however, vary significantly from year to year depending on phenomena such as El Niño and La Niña.

"Natural climate variability plays a major role in the carbon cycle. In the near future, however, climate change may cause ecosystems to become a greater source of greenhouse gases. Fires can release more carbon emissions into the atmosphere, while warmer oceans absorb less CO2. More CO2 will therefore remain in the atmosphere, accelerating global warming. These climate feedbacks are critical for human society," warned WMO Deputy Secretary-General Ko Barrett.