The change measured by the Mauna Loa Observatory was likely driven by wildfires and continued burning of fossil fuels, scientists say

Sara Hashemi

January 21, 2025 3:53 p.m.

Earth has broken another greenhouse gas emissions record: The levels of carbon dioxide in the atmosphere above Hawaii made an unprecedent jump in 2024, according to a new analysis by the Met Office, the United Kingdom’s national climate and weather service.

Between 2023 and 2024, the concentration of carbon dioxide in the atmosphere rose by 3.58 parts per million (ppm), to reach a total of 427 ppm—the largest increase between calendar years, as measured by Hawaii’s Mauna Loa Observatory, since records began 67 years ago.

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Scientists say that a “safe” concentration of atmospheric carbon dioxide is 350 ppm and that keeping this number below 430 ppm is essential for limiting warming to 1.5 degrees Celsius above pre-industrial levels, as directed in the Paris Agreement.

The new numbers signal that atmospheric carbon dioxide concentrations are not only rising—they’re doing so faster than ever, as the scientists involved in the analysis write in Carbon Brief.

“We’re still going in the wrong direction,” says Richard Betts, a climate scientist at the Met Office who worked on the analysis, to New Scientist’s Michael Le Page.

The Mauna Loa Observatory is one of the longest-running carbon dioxide monitors in the world. While its data reveal trends in global atmospheric carbon dioxide over long time periods, the scientists note that its year-to-year measurements can fluctuate as a result of localized phenomena, such as fires. Case in point: Satellites calculated the annual rise in atmospheric carbon dioxide to be 2.9 ppm over the same period—a lower number than Mauna Loa recorded, but still the second largest jump on record, after 2015 to 2016.

Scientists suggest the rise is the result of a year filled with major wildfires, record-breaking fossil fuel emissions and ongoing deforestation. Wildfires alone released billions of tons of carbon dioxide into the atmosphere—a studypublished in October found that carbon emissions from forest fires increased by 60 percent globally between 2001 and 2023. An El Niño event was also in progress for part of the year, bringing warmer and drier weather to an already warming planet.

These trends are not compatible with any of the pathways set by the Intergovernmental Panel on Climate Change (IPCC) to limit global temperature rise to 1.5 degrees Celsius (2.7 Fahrenheit), the team writes in Carbon Brief. In fact, 2024 was the first calendar year warm enough to cross that threshold. Though a single year above that marker does not mean the world breached the Paris Agreement, many top climate scientists predict temperatures will rise to at least 2.5 degrees Celsius (4.5 Fahrenheit) above pre-industrial levels.

The Met Office analysis also forecasts a further rise in atmospheric carbon dioxide concentrations for 2025. “You could regard [these findings] as another nail in the coffin of 1.5C,” says Betts to New Scientist. “That’s now vanishingly unlikely.”

Still, scientists say the work underscores the need to take climate action. “Countries have agreed to the 1.5C global warming limit not out of convenience but out of necessity to limit harm and suffering of people,” Joeri Rogelj, director of research at the Grantham Research Institute on Climate Change and the Environment who was not involved in the analysis, says in a statement. “Even if we are on track to surpass 1.5C, these reasons don’t change and only make a stronger case for focused action on reducing greenhouse gas pollution.”

Betts offers some hope to the Guardian’s Damian Carrington: “Even if it looks like we won’t meet the ambitious Paris goal of 1.5C, it is still worth making every effort to limit the rise. 1.5C is not a cliff-edge after which all is lost. There are lots of solutions already available without any new inventions. This must be extra motivation to work even harder.”