Methane, the second most significant anthropogenic greenhouse gas after carbon dioxide, increased at an unprecedented rate in the early 2020s, before slowing down from 2023 onwards. An international study led by the LSCE (CEA/CNRS/UVSQ) sheds light on the mechanisms behind this surge. The results show that the combination of the global health crisis and extreme weather events has profoundly disrupted the balance of the atmosphere.
By analysing satellite observations, ground measurements and atmospheric chemistry data, and using advanced computer models, researchers have identified two factors: lower uptake in the atmosphere due to reduced 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 accounts for about 80% of the annual variation in methane growth. These radicals play a key role in ‘cleaning’ the atmosphere by destroying methane. When their concentration decreased, methane accumulated much more rapidly.
This decline in radicals is partly linked to lockdowns during the COVID-19 pandemic. The reduction in emissions of certain air pollutants, such as nitrogen oxides and carbon monoxide, has altered the chemistry of the air and temporarily weakened the atmosphere’s ability to remove methane.
The amplifying role of climate and wetlands
Added to this first factor was a real increase in natural methane emissions, particularly those from wetlands (marshes, lakes, waterlogged soils). Between 2020 and 2023, a climatic period marked by wetter conditions (La Niña) promoted microbial activity in these environments, particularly in tropical Africa and South-East Asia, leading to an increase in methane emissions. Conversely, wetlands in South America experienced a marked decline in 2023 during an extreme drought linked to the El Niño phenomenon.
Researchers emphasise that current methane emission models still significantly underestimate the role of wetlands and flooded ecosystems. These findings call for enhanced environmental monitoring, a better understanding of microbial processes, and more detailed integration of atmospheric chemistry and climate variability.
Contrary to some assumptions, the study shows that emissions from fossil fuels and forest fires have played only a minor role in the recent increase in methane. Isotopic analyses confirm that microbial sources (wetlands, inland waters and agriculture) have been the main drivers of the observed increase.
A warning signal for climate research and policy
“By providing the most recent global assessment of methane, our study demonstrates that methane reacts very quickly to global changes, either linked to climate or related to human activities. Understanding these mechanisms is essential for better anticipating climate change and guiding emission reduction policies” explains Philippe Ciais, CEA Research Director at LSCE.
By providing an integrated view of the interactions between climate, atmospheric chemistry and natural emissions, this study provides essential keys to better monitoring methane trends on a global scale. It also serves as a reminder that fighting climate change requires a detailed understanding of our planet’s natural balances, which are sometimes fragile.
Références
“Why methane surged in the atmosphere during the early 2020s”, Science, février 2026. DOI
Reproduced from: https://www.cea.fr/drf/Pages/Actualites/En-direct-des-labos/2026/dans-les-coulisses-de-l-envolee-du-methane.aspx.
