Why global methane levels spiked during COVID lockdowns

Six years ago, as countries around the world went into COVID lockdowns, the air got cleaner. Factories slowed down, roads emptied and aeroplanes were grounded. As people stayed home, the world burned fewer fossil fuels and so carbon dioxide emissions dropped – by around 7% in 2020.

But something else was also happening in the atmosphere. Levels of methane – an extremely potent greenhouse gas that warms the planet even faster than CO₂ – rose faster in 2020 than at any point since records began in the 1980s. And methane levels kept on rising during 2021 and 2022.

Ever since, scientists have been trying to piece together what caused this sudden mysterious increase in methane. Now, they think they have the answer, and it was partly due to COVID lockdowns.

In this episode of The Conversation Weekly podcast, we speak to Philippe Ciais, a researcher at the Laboratory for Climate and Environmental Sciences at Université Paris-Saclay in France, and one of the authors of a new study in the journal Science about the spike in methane levels, who explains how they solved the mystery.

The atmosphere contains a special type of cleaning agent called hydroxyl radical (OH) which is capable of breaking down methane. Ciais calls it the “pacman of the atmosphere”. The production of these OH particles is facilitated by pollution, including nitric oxide and nitrogen dioxide (known collectively as NOx) from combustion processes.

“ In the chain of complex chemical reactions in the atmosphere that leads to the formation of NOx, OH is generated,” says Ciais. “When you have a reduced emission of NOx, as it was the case during the COVID, you have a weakening of OH … less concentration of this cleaning agent, and as a result, methane increasing faster in the atmosphere”.

The study found that around 80% of the spike in methane was caused by a reduction in OH, but increases in methane from wetlands and from agriculture also played a role.

Ciais says understanding where the growth in methane came from doesn’t mean the world should go on polluting. Rather, it’s a wake-up call. “ It’s not by continuing to drive more that we will reduce methane. It’s by reducing [methane] emissions,” he said. “That’s the ultimate way we have to prevent methane from increasing and amplify the warming of the climate.”

Listen to the interview with Philippe Ciais on The Conversation Weekly podcast. This episode was written and produced by Mend Mariwany, Katie Flood and Gemma Ware. Mixing by Eleanor Brezzi and theme music by Neeta Sarl.

Listen to The Conversation Weekly via any of the apps listed above, download it directly via our RSS feed or find out how else to listen here. A transcript of this episode is available via the Apple Podcasts or Spotify apps.

Philippe Ciais a reçu des financements de la Fondation BNP Paribas (don philanthropique pour le Global Carbon Altas), du projet financé par 4C EU Horizon2020 et du projet Climate Change Initiative de l'Agence spatiale européenne.