In 2024, the level of carbon dioxide that will warm the planet has increased more than ever

Levels of the most significant planet-warming gas in our atmosphere have risen faster than ever before, scientists say, leaving a key global climate target hanging in the balance.

Carbon dioxide (CO2) concentrations are now more than 50% higher than before humans began burning large amounts of fossil fuels.

Fossil fuel emissions were at a record high last year, while nature struggled to absorb as much CO2 as possible due to factors such as wildfires and drought, so more accumulated in the atmosphere.

The rapid rise in CO2 is “incompatible” with an international pledge to try to limit global warming to 1.5 degrees above pre-industrial levels, according to the Met Office.

It was an ambitious goal set by nearly 200 countries at a landmark UN meeting in Paris in 2015 in hopes of averting some of the worst effects of climate change.

This was confirmed last week The year 2024 became the hottest in the entire history of observationsand the first calendar year in which the average annual temperature was above 1.5C above pre-industrial levels.

It has not breached the Paris target, which refers to the long-term average value over decades, but the steady increase in atmospheric CO2 is effectively forcing the world to do so.

“To limit global warming to 1.5 degrees Celsius, it would be necessary to slow the growth of CO2, but in fact the opposite is happening,” says Richard Betts of the Met Office.

The long-term increase in CO2 is undoubtedly due to human activity, mainly through the burning of coal, oil and gas and deforestation.

Records of Earth’s climate in the distant past from ice cores and marine sediments show that CO2 levels are currently at their highest level in at least two million years, according to the UN.

But growth varies from year to year due to differences in how nature absorbs carbon, as well as fluctuations in human emissions.

CO2 emissions from fossil fuels hit new highs last year, according to preliminary data from the Global Carbon Project.

There were also consequences of art the natural phenomenon of El Niño – where surface waters in the eastern tropical Pacific become unusually warm, which affects weather conditions.

Nature has absorbed about half of humanity’s CO2 emissions, for example through additional plant growth and most of the gas that dissolves in the ocean.

But this extra burst of warmth from El Niño amid climate change meant that natural carbon sinks on land weren’t taking in as much CO2 as they normally would last year.

Large wildfires, including in regions not normally affected by El Niño, also caused additional CO2 emissions.

“Even without a stronger El Niño effect last year, the rise in CO2 from fossil fuel burning and deforestation would now be ahead of the IPCC’s (UN Climate Body) 1.5C scenarios,” says Professor Betts.

These factors mean that between 2023 and 2024, CO2 levels increased by almost 3.6 ppm to a new high of more than 424 ppm.

This is a record annual increase since atmospheric measurements were first taken at the remote Mauna Loa research station in Hawaii in 1958. Located high on a volcanic slope in the Pacific Ocean, the station is far from major sources of pollution, making it ideal for monitoring global CO2 levels.

“These latest results further confirm that we are moving into uncharted territory faster than ever as growth continues to accelerate,” says Professor Ralph Keeling, who leads the measurement program at the Scripps Institution of Oceanography in the US.

The record increase raises concerns that nature may become less able to absorb the planet-warming gases in the long term.

According to the US scientific group NOAA, the arctic tundra is becoming a common source of CO2 due to warming and frequent fires.

The the ability of the Amazon rainforest to absorb CO2 also suffers from drought, forest fires and deliberate deforestation.

“It’s an open question, but it’s something we have to keep a close eye on and look at very carefully,” Professor Betts tells the BBC.

The Met Office predicts that the increase in CO2 concentrations in 2025 will be less extreme than in 2024, but still well outside the 1.5C target plan.

La Niña conditions — when surface waters in the eastern tropical Pacific are cooler than normal — have replaced El Niño, which typically allows the natural world to absorb more CO2.

“While there may be a temporary respite with slightly cooler temperatures, warming will resume because CO2 is still building up in the atmosphere,” says Professor Betts.