1362. Atmospheric Greenhouse Gas Concentrations Reach New Records in 2024

According to the latest observations from the World Meteorological Organization (WMO) network, global mean surface concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) reached unprecedented levels in 2024, measuring 423.9±0.2 ppm for CO2, 1942±2 ppb for CH4, and 338.0±0.1 ppb for N2O. These values represent 152%, 266%, and 125%, respectively, of pre-industrial levels (before 1750).

In particular, global atmospheric CO2 concentrations increased by 3.5 ppm from 2023 to 2024, marking the largest annual increase since modern observations began in 1957. This increase was driven by continued fossil fuel CO2 emissions, increased emissions from fires, and a decrease in terrestrial and marine carbon sinks in 2024, and may be a sign of climate feedback. Given the dominant role of atmospheric CO2 increases in global climate change, continued and expanded greenhouse gas monitoring is essential to support efforts to achieve net-zero anthropogenic CO2 emissions.

For CH4, the increase from 2023 to 2024 was lower than the increase observed from 2022 to 2023 and lower than the average annual increase rate over the past decade (2014 to 2023).For N2O, the increase from 2023 to 2024 was also lower than the increase observed from 2022 to 2023 and slightly lower than the average annual increase rate over the past decade. According to the National Oceanic and Atmospheric Administration's (NOAA) Annual Greenhouse Gas Index (AGGI), radiative forcing from long-lived greenhouse gases (LLGHGs) increased by 54% between 1990 and 2024, with CO2 accounting for approximately 81% of this increase.

Contributor: IIYAMA Miyuki IIYAMA, Information Program