Global greenhouse gas concentrations set another record high last year.
The global average concentration of carbon dioxide reached 426.8 parts per million last year, with methane at 1,948 parts per billion and nitrous oxide at 339.1 ppb, according to the 22nd Greenhouse Gas Bulletin released by the World Meteorological Organization on the 27th. The levels stand at 153%, 267% and 126%, respectively, of concentrations in 1750, before industrialization, and mark the highest readings since observations began in 1957. A concentration of 1 ppm means one in every million air particles is a greenhouse gas particle, while 1 ppb means one in every billion.
The pace of increase slowed somewhat. The annual average rise in carbon dioxide was 2.8 ppm, down from 3.5 ppm a year earlier. The WMO attributed the slowdown to the recovery of forests and soils that had been weakened by high temperatures and drought caused by a strong El Nino in 2023 and 2024. Carbon emissions from wildfires also declined.
Methane concentrations rose 6 ppb from a year earlier, below the average annual increase of 10 ppb over the past decade. Nitrous oxide rose 1.1 ppb, in line with the 1.1 ppb average annual increase over the same period.
Background concentrations of all three gases in Korea were higher than the global averages. Domestic carbon dioxide measured 432.7 ppm last year, with methane at 2,023 ppb and nitrous oxide at 340.6 ppb. Average annual increases over the past decade were 2.7 ppm, 9 ppb and 1.2 ppb, respectively. The Korea Meteorological Administration calculates domestic concentrations by averaging background readings taken at Anmyeondo, Gosan on Jeju Special Self-Governing Province and Ulleungdo.
The bulletin placed particular emphasis on the need to monitor sulfur hexafluoride and hydrogen. Sulfur hexafluoride remains in the atmosphere for more than 1,000 years and has about 24,300 times the impact on global warming over a 100-year period as the same amount of carbon dioxide. Its concentration has risen over the past three decades, and last year's annual increase was the largest on record. Hydrogen is not a greenhouse gas but contributes indirectly to global warming by slowing the breakdown of methane in the atmosphere.
Sulfur hexafluoride is used as an insulating gas in power transmission and distribution equipment, while hydrogen serves as an energy carrier replacing fossil fuels. Both are used in the energy transition, but leaks into the atmosphere could partly offset the emissions reductions the transition is meant to deliver.
The Korea Meteorological Administration has monitored sulfur hexafluoride since 2007 and has operated the WMO's World Calibration Centre for the gas since being designated in 2012. "Based on the agency's long-term continuous observation data and its capacity to operate the World Calibration Centre for sulfur hexafluoride, we will deepen scientific understanding of greenhouse gas changes globally and in Korea and support the country's carbon neutrality policy," KMA Administrator Lee Mi-sun said.
