A significant anomaly in the climate system has emerged with a record annual increase in the global mean concentration of carbon dioxide in 2024.
Since the mid-1800s, when human activity began burning coal and oil, the atmospheric concentration of carbon dioxide has risen sharply from the pre-industrial level of 280 parts per million (ppm).
In recent years, annual increases were typically 1 to 2 ppm. However, the National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory reported a 3.75 ppm increase last year, based on early April data.
This brings the global concentration close to 430 ppm, marking a 40% rise since pre-industrial times, sufficient to raise the planet’s temperature by about 2.7 degrees Fahrenheit (1.5 degrees Celsius). This trend challenges the Paris Agreement target to limit warming to 2.7 degrees Fahrenheit above pre-industrial levels.
“The large increase in 2024 is concerning,” said Berkeley Earth climate researcher Zeke Hausfather. “While expected due to ongoing emissions and El Niño effects, 2024’s increase was unusually high.”
El Niño, the warm phase of the tropical Pacific Ocean cycle, often results in higher ppm increases, as seen in 1998 and 2016 with about 3 ppm increases, Hausfather noted.
“Given stable emissions and ocean absorption, this suggests a weakening land sink,” he said, referring to carbon absorption by ecosystems like forests. While these ecosystems still absorbed carbon last year, the land sink was the weakest since 1998 and 1987.
Even if growth slows in 2025, Hausfather warned that factors beyond El Niño, such as temperature responses from soils, may persist or intensify with warming.
The exceptional rise in atmospheric CO2 is among several climate indicators raising concern.
Other concerns include the 2023-2024 surge in global surface temperature and the continuous breach of the Paris Agreement’s 2.7 degree Fahrenheit target over the past 21 months. Additionally, polar sea ice extent has reached record lows, diminishing Earth’s heat shields.
NOAA traditionally shares annual greenhouse gas updates via press releases, but internal communication might change due to recent staffing shifts, according to Tom Di Liberto, a former NOAA public affairs specialist.
“NOAA’s usual reports might not be publicized as before,” he said. NOAA did not comment on the 2024 CO2 increase.
Climate scientist Michael Mann from the University of Pennsylvania suggested the CO2 spike could reflect emissions rebounding post-COVID, anticipating emissions to plateau soon due to global decarbonization efforts.
James Hansen of Columbia University linked the 2024 CO2 rise to ongoing high emissions and warm oceans. However, he noted that the airborne fraction of emissions is declining, hinting at potential decreases in CO2 growth with reduced emissions.
Original Story at insideclimatenews.org