Carbon dioxide levels in the atmosphere soared by a record amount to new highs in 2024, committing the planet to more long-term temperature increases over many centuries, the World Meteorological Organisation (WMO) has warned.
In its annual Greenhouse Gas Bulletin published on Wednesday, the WMO said the world is threatened by “a vicious climate cycle”.
This is due to a combination of continued CO2 emissions from human activities and an upsurge from wildfires. It is exacerbated by reduced CO2 absorption by “carbon sinks” such as land ecosystems including forestry and boglands as well as oceans.
Growth rates of CO2 have tripled since the 1960s, the bulletin adds. It accelerated from an annual average increase of 0.8 parts per million (ppm) per year to 2.4ppm from 2011 to 2020. From 2023 to 2024, global average concentration of CO2 surged by 3.5ppm – the largest increase since modern measurements started in 1957.
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“The heat trapped by CO2 and other greenhouse gases is turbocharging 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 wellbeing,” said WMO deputy secretary general Ko Barrett.
Concentrations of methane and nitrous oxide – the second and third most important long-lived greenhouse gases related to human activities – have also risen to record levels.
The WMO released the bulletin to provide authoritative scientific information for the UN climate change conference in November (Cop30), in Belém, Brazil.
“Sustaining and expanding greenhouse gas monitoring are critical to support such efforts,” said Oksana Tarasova, co-ordinator of the bulletin.
When the bulletin was first published in 2004, the annual average level of CO2 measured at WMO monitoring stations was 377.1ppm. In 2024, it was 423.9ppm.
About half of the total CO2 emitted each year remains in the atmosphere; the rest is absorbed by Earth’s land ecosystems and oceans. However, this storage is not permanent. As global temperature rises, oceans absorb less CO2 because of decreased solubility at higher temperatures, while land sinks are impacted negatively, including more persistent drought.
The likely reason for record growth between 2023 and 2024 is a surge in wildfire emissions and a reduced uptake of CO2 by land and the oceans, combined with a natural warming phenomenon.
“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 Ms Tarasova.
Methane accounts for about 16 per cent of the warming but has a lifetime of about nine years. Approximately 40 per cent of methane is emitted by natural sources (such as wetlands) which are sensitive to climate as well. About 60 per cent comes from anthropogenic sources such as cattle, rice farming, fossil fuel exploitation, landfills and biomass burning.
Nitrous oxide comes from both natural sources and human activities including biomass burning, fertiliser use and industrial processes.
Meanwhile, the UK Climate Change Committee has warned Britain must prepare for global heating far in excess of the level scientists have previously suggested as the limit of safety, as current plans to protect against extreme weather are inadequate. This could mean a two-degree rise by 2050.
Heatwaves will occur in at least four of every five years in England by 2050 and time spent in drought will double, it predicted. The number of days of peak wildfire conditions in July will nearly treble, while floods will increase in frequency throughout the year, with some peak river flows increasing by 40 per cent.
