Carbon dioxide emissions to hit 429.6 ppm in May 2025, highest in over 2 million years

Atmospheric carbon dioxide levels, which registered the steepest annual increase between 2023 and 2024, are projected to remain alarmingly high this year as well, according to a forecast of measurements from Mauna Loa Observatory in Hawaii published by the Met Office, UK, on January 17, 2025.

In May 2025, atmospheric carbon dioxide levels are forecast to be 429.6 ppm. This will be the highest atmospheric CO2 concentration for over 2 million years.

This is an increase of approximately 2.26 ppm between 2024 and 2025 and do not align with the Intergovernmental Panel on Climate Change (IPCC) scenarios for limiting global warming to 1.5°C.

To limit global warming to 1.5°C, as outlined in the Paris Agreement, the accumulation of CO2 and other greenhouse gases in the atmosphere must first decelerate and then reverse. According to the IPCC, this requires the current CO2 build-up in the atmosphere to slow to approximately 1.8 ppm per year.

However, the atmospheric CO2 concentrations continue to rise with no signs of slowing. In 2024, carbon dioxide levels increased at the fastest annual rate ever recorded in the long-standing measurements at Mauna Loa, Hawaii, which began in 1958, exceeding projections by the Met Office.

The recorded annual rise of 3.58 parts per million (ppm) between 2023 and 2024 surpassed the predicted increase of 2.84 ppm, with satellite data confirming substantial increases worldwide.

The record increase in atmospheric CO2 concentrations was driven by a combination of factors, including record-high fossil fuel emissions, reduced carbon capture by natural sinks such as tropical forests, and massive CO2 releases from wildfires, according to a study by the Met Office.

When forests burn, they release vast amounts of stored CO2.  For instance, global wildfires in 2023 emitted 7.3 billion tonnes of CO2, as per the EU’s Copernicus Atmosphere Monitoring Service (CAMS).

The global carbon emissions from fossil fuels hit a record high in 2024 and are estimated to be 41.6 billion tonnes in 2024, up from 40.6 billion tonnes in 2023.

While the annual average CO2 concentration is projected to further increase to 426.6 ppm this year, it is slower as compared to last year’s record increase.

But even this slower rise will still be too fast to track the IPCC’s scenarios that limit global warming to 1.5°C with little or no overshoot.

What this means

Carbon dioxide in the atmosphere acts as a heat trap, with higher concentrations trapping more heat and gradually raising global temperatures. This leads to increasingly severe impacts, including rising sea levels, more extreme droughts, storms, and floods, as well as harm to wildlife and essential natural systems.

The accumulation of CO2 and other greenhouse gases in the atmosphere has already pushed global climate to dangerously high temperatures. In 2024, global temperatures surpassed those of 2023, making it the warmest year on record. According to the World Weather Attribution’s annual analysis, extreme weather events reached unprecedented levels in 2024, highlighting the escalating risks of climate change.

The record-breaking temperatures in 2024, fueled unrelenting heatwaves, drought, wildfire, storms and floods that killed thousands of people and forced millions from their home.

In India, at least 3,200 were killed due to extreme weather events as per the India Meteorological Department’s (IMD) Annual Climate Summary, 2024.

The World Meteorological Organization (WMO) predicts that global temperatures will keep rising through 2025, making it likely one of the three hottest years on record. This trend is expected to intensify the effects of extreme weather events, which are ranked as the second most severe global risk for 2025-2027. The risk also appears in the top five across 28 countries, up from 24 last year.

Professor Richard Betts, who leads the forecast production at the Met Office, stated, “The long-term warming trend will persist because CO2 continues to accumulate in the atmosphere.”

He added, “While La Niña conditions are expected to result in forests and other ecosystems absorbing more carbon than last year, temporarily slowing the rise of atmospheric CO2, halting global warming requires a complete stop in the buildup of greenhouse gases followed by a reduction. Significant and rapid cuts in emissions could help limit how much global warming exceeds 1.5°C, but this demands urgent international action.”