The Mauna Loa Observatory in Hawaii has been recording atmospheric carbon dioxide levels since 1958.
COURTESY OF FRED ESPENAK/SCIENCE PHOTOGRAPHY
A weather station at Hawaii’s Mauna Loa Observatory predicted atmospheric carbon dioxide levels would increase by 3.58 parts per million in 2024, the largest jump since records began in 1958.
“We are still going in the wrong direction,” says the climate scientist Richard Betts At the Met Office, the UK weather service.
The record increase is partly due to CO2 emissions from burning fossil fuels and other human activities such as deforestation, which reached a record in 2024. world temperature record driven by El Niño weather pattern on long-term warming.
It’s Betts predicts atmospheric CO2 levels As measured at Mauna Loa, this year it will rise by 2.26 parts per million (ppm), with a margin of error of 0.56 ppm. That’s well short of the 2024 record, but it would put us well over the last possible path to limiting the rise in global surface temperatures to 1.5°C above pre-industrial levels.
“You can think of it as another nail in the coffin of 1.5°C,” says Betts. “Now it’s very difficult to disappear.”
Atmospheric CO2 levels are the most important measure of climate change, as the increase in atmospheric CO2 is the main factor driving both short-term and long-term warming. The first measurements of CO2 levels were made at Mauna Loa.
“Because this station has the longest time record and is far from major anthropogenic and natural CO2 emissions and sinks, it is often used to represent global change in CO2 concentrations,” he says. Richard Angels In the EU’s Copernicus Atmospheric Monitoring Service.
With satellite observations, however, it is now possible to directly measure the global average level of CO2 in the atmosphere. According to CAMS, it increased to 2.9 ppm in 2024. That’s not a record, but it’s one of the biggest increases since satellite observations began.
“The reason for this larger increase needs further investigation, but it is likely to be a combination of the rebound in emissions in large parts of the world after the covid pandemic together with inter-annual changes in the natural carbon sink,” says Engelen. The carbon sink refers to the oceans and ecosystems on land, which have absorbed about half of human-caused CO2 emissions.
It has long been predicted that as the planet warms, less of this excess CO2 will be absorbed. “Whether or not this is the start of it is worrying,” says Betts. “We don’t know.”
At Mauna Loa, the increase in CO2 is higher than the global average level in 2024 because of the number of fires in the northern hemisphere, says Betts. It takes time for CO2 plumes from sources like wildfires to mix evenly in the atmosphere around the world. “Fire emissions in the Northern Hemisphere were particularly high last year,” he says.
Although it is now certain that global warming will exceed the 1.5°C limit, Betts believes it was still right to set this as a target. “The Paris Agreement was written very carefully: to achieve the results of limiting warming to 1.5. It was recognized at the beginning that it was going to be a challenge,” he says. ».
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