Levels of the three most abundant long-lived greenhouse gases (GHG) in the world's surface atmosphere "reached unprecedented highs in 2024", with the CO2 increase the largest recorded, the World Meteorological Organisation (WMO) said today.
The level of CO2 rose between 2023-24 by 3.5 parts per million (ppm), the biggest yearly increase since modern measurements began in 1957, the WMO said in its Greenhouse Gas Bulletin, which it releases ahead of annual UN Cop climate conferences. This was "most likely due to a combination of natural variability and continued emissions of fossil fuel CO2", it said.
CO2 stood at 423.9 ppm, methane at 1,942 parts per billion (ppb) and nitrous oxide at 338 ppb in 2024, WMO data show, respectively 152pc, 266pc and 125pc of pre-industrial levels.
CO2 is the "dominant [long-lived GHG] driving global climate change", and CO2 emissions from fossil fuels "represent the vast majority of overall [GHGs]", the WMO said. CO2 is "responsible for about 79pc of the increase in radiative forcing over the past decade", it said.
Around half of CO2 emissions have been absorbed by land ecosystems and oceans, but this is not necessarily permanent sequestration, the WMO said. Climate change leads to lower CO2 uptake, as weather extremes and rising ocean temperatures put land ecosystems under stress and cause decreased solubility in oceans. Carbon sinks can be reduced through forest fires and wildfires, which also produce CO2 emissions.
The increase in methane and nitrous oxide in 2023-24 was lower than that recorded for 2022-23, and also below the average annual growth rate in 2014-23, WMO said.
Worldwide temperatures hit record highs last year. The average global temperature in 2024 was also likely to have breached 1.5°C above pre-industrial levels — the more ambitious temperature threshold sought by the Paris climate agreement.
