In a year marked by record-breaking heat, another alarming milestone has quietly fallen: carbon dioxide levels in Earth’s atmosphere rose faster in 2024 than ever before recorded.
Scientists tracking the data say the leap in CO₂ the main gas driving global warming casts serious doubt over the world’s ability to meet the Paris Agreement goal of limiting temperature rise to 1.5°C above pre-industrial levels.
“Limiting global warming to 1.5C would require the CO₂ rise to be slowing. But in reality, it’s accelerating,” said Professor Richard Betts of the UK’s Met Office. “That’s simply not compatible with the goal we set in Paris.”
Record Heat, Record Emissions
Last year was officially the hottest ever recorded, with average global temperatures breaching 1.5°C for the first full calendar year. While this does not yet violate the Paris Agreement which is based on longer-term trends the trajectory is worrying.
The jump in atmospheric CO₂ was driven by a combination of record fossil fuel use, more carbon-releasing wildfires, and droughts that limited nature’s ability to absorb emissions.
Data from the Global Carbon Project shows emissions from oil, gas, and coal reached unprecedented levels in 2024. But natural systems that usually soak up around half of those emissions forests, soil, and oceans struggled under the heat.
In total, CO₂ concentrations rose by nearly 3.6 parts per million (ppm) in a single year, hitting a new high of over 424ppm, according to readings from Mauna Loa Observatory in Hawaii. That’s the largest annual jump since records began in 1958.
Nature’s Sinks Under Strain
This spike was partly fuelled by El Niño, a natural climate pattern that warms ocean waters in the Pacific and disrupts weather globally. The added heat intensified drought and fire conditions, weakening ecosystems that usually absorb carbon.
Wildfires many sparked or worsened by the heat spread across the Amazon, Canada, and parts of Europe, releasing more carbon than normal. The Amazon, often called “the lungs of the Earth,” is showing signs of strain.
“Drought, fire, and deforestation are taking a toll on the Amazon’s ability to act as a carbon sink,” said Professor Ralph Keeling of the Scripps Institution of Oceanography. “We’re seeing parts of it shift from absorbing CO₂ to releasing it.”
The Arctic tundra is also changing. According to the US National Oceanic and Atmospheric Administration (NOAA), it is becoming a net source of carbon, as permafrost thaws and fires become more common.
“These ecosystems aren’t limitless buffers. They have breaking points, and we’re pushing them,” said Betts.
A Glimpse Into the Past — and the Future
Analysis of ancient ice cores and sediments confirms what scientists have long feared: CO₂ levels are now higher than at any point in at least two million years. The last time Earth had similar concentrations, sea levels were metres higher, and temperatures much warmer.
What’s changed now is the speed. Never in recorded geological history has CO₂ risen this fast.
“This is uncharted territory,” said Keeling. “We’ve left the range of natural variability far behind.”
The Met Office predicts that the rise in CO₂ could ease slightly in 2025, thanks to the shift from El Niño to La Niña, which tends to cool global temperatures and help forests and oceans absorb more carbon. But this relief may be temporary.
“Even if next year’s increase is smaller, the long-term trend is still going the wrong way,” Betts warned. “And every tonne we add makes it harder to turn around.”
A Turning Point — or Tipping Point?
As countries prepare for the next UN climate summit later this year, pressure is mounting to close the gap between climate pledges and actions.
Cutting fossil fuel use is still seen as the most effective way to reduce CO₂. But many nations continue to approve new oil and gas projects, even as global temperatures rise.
Scientists say the world is rapidly approaching or may already have passed thresholds that could lead to irreversible environmental changes.
“We know what needs to happen: emissions must fall, fast and steeply,” said Betts. “But year after year, the numbers tell a different story.”
With CO₂ rising faster than ever, the path to 1.5°C is narrowing. And time, scientists warn, is running out.
