🫧 Why has the amount of methane increased sharply since 2019?

In the atmosphere, the amount of methane, the second most significant human-made greenhouse gas after carbon dioxide, increased at an unprecedented rate in the early 2020s.

An international study published on February 5, 2026 in the journal Science, involving scientists from the Climate and Environmental Sciences Laboratory (LSCE - CEA/CNRS/UVSQ), now sheds light on the mechanisms behind this surge. The results show that the combination of the global health crisis and extreme climate events profoundly altered the atmosphere's balance.


In the early 2020s, the amount of methane increased at a rate unprecedented since the beginning of measurements, before slowing down from 2023. By analyzing satellite observations, ground measurements, atmospheric chemistry data, and using advanced computer models, a study led by the LSCE highlighted two factors: its reduced uptake in the atmosphere due to lower pollutant emissions and increased emissions from wetlands.

A decrease in emissions of certain pollutants during lockdown

The study shows that a sharp decline in hydroxyl radicals between 2020 and 2021 explains about 80% of the annual variation in methane growth. Indeed, these radicals are produced by ultraviolet radiation which transforms certain air pollutants into highly reactive molecules and play a key role in the "cleansing" of the atmosphere by destroying methane. When their concentration decreased, methane accumulated much faster.

This decline in radicals is partly linked to the lockdowns during the Covid-19 pandemic. The reduction in emissions of certain atmospheric pollutants, such as nitrogen oxides and carbon monoxide, indeed altered air chemistry and temporarily weakened the atmosphere's ability to remove methane by reducing the concentration of these radicals.

Amplifying role of climate and wetlands

To this first factor was added a real increase in natural methane emissions, particularly those from wetlands (marshes, lakes, water-saturated soils). Between 2020 and 2023, a climatic period marked by wetter conditions (La Niña) favored microbial activity in these environments, particularly in tropical Africa and Southeast Asia, leading to a rise in methane emissions. Conversely, wetlands in South America experienced a marked decline in 2023, during an extreme drought linked to the El Niño phenomenon.

The researchers point out that current methane emission models still largely underestimate the role of wetlands and flooded ecosystems. These results argue for strengthening environmental monitoring, a better understanding of microbial processes, and a finer integration of atmospheric chemistry and climate variability.

Contrary to some hypotheses, the study shows that emissions from fossil fuels and forest fires played a limited role in the recent increase in methane. Isotopic analyses confirm that microbial sources (wetlands, inland waters, and agriculture) were the main drivers of the observed increase.

A warning signal for research and climate policies

"By providing the most recent global methane budget, our study demonstrates that methane reacts very quickly to global changes, whether climatic or related to human activities. Understanding these mechanisms is essential to better anticipate climate evolution and guide emission reduction policies," explains Philippe Ciais, a CEA climatologist at the LSCE and lead author of the study.

By providing an integrated view of the interactions between climate, atmospheric chemistry, and natural emissions, this study provides essential keys to better track the evolution of methane on a global scale. It also reminds us that the fight against climate change requires a detailed understanding of our planet's natural, sometimes fragile, balances.