New Delhi: The concentration of methane in the atmosphere accelerated sharply in the early 2020s, reaching unprecedented levels in comparison to prior decades. Then methane spike intensified global warming during a critical time for climate action. Now, a team of researchers from Peking University, in collaboration with international partners have identified the key mechanism driving this dramatic surge. The researchers combined satellite data, ground-based observations and advanced models to show that a temporary weakening of methane removal, combined with climate-driven natural emissions drove the surge. Methane is the second most important greenhouse gas than carbon dioxide, and has about 80 times more warming power than carbon dioxide over a period of 20 years.

Methane accounts for about one-third of the current contribution to global warming, and exerts a powerful short-term climate effect. Methane is also far more difficult to scrub from the atmosphere than carbon dioxide. The study found that atmospheric hydroxyl radicals, the primary oxidant responsible for removing methane declined sharply between 2020 and 2021. The temporary weakening of the methane sink explains about 80 per cent of the yearly variability in methane between 2019 and 2023. The COVID-19 pandemic also resulted in reduced nitrogen oxide emissions, that contributed to the lower hydroxyl levels, allowing methane to build up more rapidly in the atmosphere.

A cascade of natural causes

There was an extended La Nina event between 2020 and 2023, bringing wetter-than-average conditions across tropical regions. Expanded wetlands and inland waters in tropical Africa and Southeast Asia, along with increased emissions from Arctic wetlands and lakes significantly boosted the production of microbial methane. Fossil fuel and wildfire emissions played only a minor role in the surge. The research indicates that future methane trends will not depend only on anthropogenic emissions, but also on natural sources of methane, providing scientific evidence for future methane mitigation plans, and responses to climate change. A paper describing the research has been published in Science.