Planet-Warming Greenhouse Gas Concentrations Surged to Historic Levels in 2025, WMO Says

In 2025, atmospheric concentrations of major greenhouse gases surged to record levels, according to the World Meteorological Organization (WMO). Carbon dioxide (CO2) concentrations, a byproduct of burning fossil fuels, reached a record high of 426.8 parts per million (ppm) - a 153% increase since the pre-industrial baseline in 1750.

CO2 is the principal anthropogenic greenhouse gas, responsible for about three-quarters of planet-warming emissions. Its long atmospheric lifespan commits the planet to rising temperatures not just for years, but for decades and even centuries.

Methane concentrations in 2025 were 1,948 parts per billion (ppb), marking a 267% increase since 1750. As the second most significant greenhouse gas, methane is 84 times more potent than CO2 in trapping heat over a 20-year period. Nitrous oxide, the third-most significant human-caused greenhouse gas, climbed to 339.1 parts per billion (ppb), 126% higher than pre-industrial levels. This gas is mainly associated with the use of nitrogen fertilizers and manure from intensified agriculture.

Despite the increase in greenhouse gas concentrations, the burning of coal, natural gas, and oil remains the single-largest source of global greenhouse gas emissions. Scientists have long warned that curbing fossil fuel extraction and consumption is crucial to halting global warming and securing a livable future. The International Energy Agency has called for an end to new gas and oil field projects to keep the 1.5C-compatible net-zero emissions scenario viable.