Concentrations of CO2, methane and nitrous oxide climbed to record levels in the global atmosphere in 2023, contributing ever more to the climate crisis. This is according to scientists from the US National Oceanic and Atmospheric Administration (NOAA).

The rise in these gases, as detected in air samples by NOAA's Global Monitoring Laboratory (GML) last year, didn't reach the record surges seen in recent times. Nonetheless, they mirrored the steep inclines observed over the past decade.

“NOAA’s long-term air sampling programme is essential for tracking causes of climate change and for supporting the US efforts to establish an integrated national greenhouse gas measuring, monitoring and information system,” said GML director Vanda Grubišić. “As these numbers show, we still have a lot of work to do to make meaningful progress in reducing the amount of greenhouse gases [GHGs] accumulating in the atmosphere.” 

CO2 levels averaged 419.3 parts per million across all twelve months of 2023, marking an annual increase of 2.8 ppm. This marked the 12th consecutive year of CO2 surging by over 2 ppm, representing the longest sustained increase recorded in the 65-year monitoring history. This notable surge in CO2 hadn't been observed prior to 2014.

 

Xin Lan, a CIRES scientist leading the synthesis of data from NOAA's Global Greenhouse Gas Reference Network, attributed the third-largest increase in 2023 to ongoing rises in fossil fuel CO2 emissions, possibly compounded by heightened fire emissions due to transitioning climatic conditions.

“The 2023 increase is the third-largest in the past decade, likely a result of an ongoing increase of fossil fuel CO2 emissions, coupled with increased fire emissions possibly as a result of the transition from La Nina to El Nino,” said Lan.

Methane, though less prevalent than CO2, displayed an average concentration of 1922.6 parts per billion in 2023. This marked a rise of 10.9 ppb from the previous year, ranking as the fifth highest since the resurgence of methane growth in 2007.

Nitrous oxide levels, another significant human-induced greenhouse gas, increased to 336.7 ppb in 2023, reflecting a rise of 1 ppb from the preceding year. Notably, the years with the highest growth since 2000 occurred in 2020 and 2021, primarily attributed to agricultural activities.

NOAA's Global Monitoring Laboratory collected over 15,000 air samples globally in 2023, analysing them in its advanced laboratory in Boulder, Colorado. These samples, drawn from sites in NOAA's Global Greenhouse Gas Reference Network, including cooperative sites, tall tower sites, and routine aircraft operation sites, are pivotal in tracking greenhouse gas trends and understanding carbon cycle dynamics.

CO2 emissions from fossil fuels, by far the main contributor to climate change, reached a new record of about 33.2 tonnes per year (tpy) in 2023. This trend, as noted by the Global Carbon Project, which uses NOAA data, underscores the urgent need for concerted efforts to mitigate carbon emissions.

The amount of CO2 in the atmosphere today is comparable to where it was around 4.3mn years ago during the mid-Pliocene epoch, said NOAA, when sea level was about 22.9 metres higher than today. Additionally, the average temperature was 3.9 degrees Celsius higher than in pre-industrial times, and large forests occupied areas of the Arctic that are now tundra, said the agency.