In 2024, wildfires raging across the globe contributed to an unprecedented surge in atmospheric carbon dioxide levels, catching scientists off guard.

This data highlights how humanity is plunging further into a world of intensified extreme weather events driven by climate change.

Measurements from the Mauna Loa Observatory in Hawaii showed a striking increase in CO2 concentrations, rising by 3.6 parts per million (ppm) to reach 427ppm. This level far exceeds the pre-industrial figure of 280ppm, which marked the period before large-scale fossil fuel consumption triggered the climate crisis. These measurements, known as the Keeling Curve, have been continuously recorded since 1958, making them the longest-running direct CO2 data series.

The steep rise in CO2 was largely attributed to emissions from forest fires, which compounded ongoing pollution from coal, oil, and gas—sources that also hit record emission levels in 2024.

The natural El Niño climate pattern exacerbated the situation by creating hotter and drier conditions in tropical regions. However, scientists indicated that even without El Niño, a record increase would likely have occurred.

Simultaneously, the global average temperature reached a new peak in 2024, intensifying heatwaves, storms, and floods that impacted billions worldwide. This year marked the first time the planet exceeded the 1.5°C (2.7°F) threshold established as a target under the Paris Climate Agreement.

UN Secretary-General António Guterres condemned the fossil fuel industry, accusing it of prioritising profits while its products wreaked havoc on the environment.

Though the 1.5°C limit is a long-term target that requires sustained warming over a decade or more to be considered officially breached, scientists noted that the CO2 surge in 2024 made staying within that target increasingly unlikely. Projections indicate that while CO2 levels may rise more slowly in 2025, they will still remain significantly above the trajectory required to keep warming below 1.5°C.

“This is obviously bad news,” said Prof Richard Betts at the UK Met Office, whose team analysed the CO₂ rises. “But 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.”

Because global heating is directly tied to rising emissions, every reduction in CO2 output translates to reduced human suffering. Effective solutions to curb carbon emissions are already available. However, an investigation in May revealed that most climate experts expect the planet to surpass the 1.5°C threshold due to continued political inaction.

In 2024, wildfires released billions of tonnes of CO2, particularly in the Americas, with climate change exacerbating their frequency and severity. Although El Niño played a role in fuelling these fires, many blazed outside its direct influence, such as those in Canada. Additionally, El Niño’s hot and dry conditions suppressed plant growth, limiting nature’s ability to absorb human-generated CO2.

The 3.6ppm increase in CO2 in 2024 was double the 1.8ppm annual rise needed to align with net-zero emissions and limit warming to 1.5°C. This spike also exceeded the UK Met Office’s prediction of 2.8ppm, likely due to wildfire emissions reaching Mauna Loa. For 2025, the Met Office forecasts a lower rise of 2.3ppm as La Niña, El Niño’s counterpart, fosters increased vegetation growth.

Addressing the UN General Assembly on Wednesday, Guterres emphasised the climate crisis as a central priority for 2025, calling for urgent global action to combat escalating emissions and environmental destruction.

“Who pays the price for climate destruction around the globe? Not the fossil fuel industry pocketing profits and taxpayer subsidies as their products wreak havoc,” he said. “Every day people suffer: with their lives and livelihoods; with higher insurance premiums, volatile energy bills, and higher food prices.”

“Today, governments around the globe spend nine times more making fossil fuels cheaper than they do on making clean energy more affordable for consumers,” blocking climate action, Guterres said. “We must tear down these walls.”