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\t\t\t\t\t\t06\/02\/2026<\/span> With fewer cars on the road, planes in the air and factories running, the skies seemed cleaner during the Covid-19 pandemic. However, while there was a decline in pollutants such as nitrogen dioxide, scientists were surprised to see that methane surged in the early 2020s and then dropped \u2013 and now they know why.<\/p>\n<\/div>\n Methane is a powerful greenhouse gas and is the second-largest contributor to climate warming after carbon dioxide.<\/p>\n A tonne of methane, despite its shorter lifespan of about 10 years in the atmosphere, can retain about 30 times more heat than a tonne of carbon dioxide over the course of a century. This means that when it comes to warming our planet, methane is a potent player.<\/p>\n Between 2020 and 2022, global concentrations surged at the fastest rate ever recorded, peaking at 16.2 parts per billion per year, before easing back to 8.6 ppb per year by 2023.<\/p>\n Using methodologies developed within the European Space Agency\u2019s Climate Change Initiative\u2019s RECCAP-2 project, a new international study, published in the journal Science<\/i>, reveals why.<\/p>\n<\/p><\/div>\n For a brief period, the atmosphere became less efficient at cleaning methane away \u2013 just as natural emissions from wetlands surged under unusual climatic conditions.<\/p>\n Philippe Ciais, from France\u2019s Laboratory for Climate and Environmental Sciences (LSCE) and lead author of the paper, explained, \u201cOur research combined satellite data, ground-based measurements, atmospheric chemistry data and advanced computer models to reconstruct the global methane budget from 2019 to 2023.<\/p>\n \u201cThe results point to a powerful and temporary shift in atmospheric chemistry as the main driver of the methane spike.\u201d<\/p>\n At the heart of the story are hydroxyl radicals \u2013 highly reactive molecules often described as the atmosphere\u2019s \u2018detergent\u2019. These radicals normally break down methane, limiting how long it remains in the atmosphere.<\/p>\n During 2020\u20132021, however, hydroxyl radicals levels around the world dropped. This is because the ingredients needed to make them were reduced when human activity slowed down.<\/p>\n<\/p><\/div>\n Hydroxyl radicals form through chemical reactions involving sunlight, ozone, water vapour and gases such as nitrogen oxides, carbon monoxide and volatile organic compounds.<\/p>\n As a result of the Covid-19 lockdowns, the emission of these gases dropped, and hence the hydroxyl radicals, which would normally destroy methane, also reduced \u2013 slowing the atmosphere\u2019s ability to remove methane.<\/p>\n According to the study, this weakening of the atmosphere\u2019s oxidising capacity explains around 80% of the year-to-year variation in methane growth over the period.<\/p>\n With fewer hydroxyl radicals available, methane accumulated faster than usual.<\/p>\n This chemical slowdown coincided with major changes in the climate. An extended La Ni\u00f1a phase from 2020 to 2023 brought wetter-than-average conditions across much of the Tropics.<\/p>\n<\/p><\/div>\n Flooded soils and expanded wetlands provided ideal conditions for methane-producing microbes, boosting emissions from wetlands and inland waters. The largest increases were seen in tropical Africa and Southeast Asia, while Arctic wetlands and lakes also released more methane as temperatures rose.<\/p>\n In contrast, South American wetlands showed a sharp drop in emissions in 2023, linked to extreme El Ni\u00f1o-related drought.<\/p>\n Crucially, the study finds that fossil fuel emissions and wildfires only played a minor role in the surge. Isotopic fingerprints in atmospheric methane instead point strongly towards microbial sources \u2013 wetlands, inland waters and agriculture \u2013 as the dominant contributors to the observed changes.<\/p>\n The findings expose important gaps in current methane emission models, many of which underestimated emissions from wetlands during this period.<\/p>\n<\/p><\/div>\n The authors highlight the need for better monitoring of flooded ecosystems, improved representation of soil and water processes, and closer integration of atmospheric chemistry with climate variability.<\/p>\n \u201cBy providing the most up-to-date global methane budget through 2023, this research clarifies why methane rose so rapidly \u2013 and why it has recently slowed,\u201d added Philippe Ciais.<\/p>\n According to Clement Albergel, ESA\u2019s Actionable Climate Information Section Head, \u201cThe study underscores the growing importance of satellites \u2013 not only for tracking greenhouse gases, but for revealing the subtle chemical processes that govern their fate in the atmosphere. It shows that climate surprises are not always about what we emit, but about how the atmosphere responds.\u201d<\/p>\n The message is clear: future methane trends will depend not only on how well humanity controls emissions, but also on air-quality policies and climate-driven changes in the planet\u2019s natural methane cycle.<\/p>\n<\/p><\/div>\n
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