Scientists have finally explained the mysterious increase in the concentration of methane, a powerful greenhouse gas, in the atmosphere in 2020: The increase was caused by wetter and warmer conditions in some regions and, ironically, by lower emissions of the polluting gas, two studies published this week. show

Researchers were surprised by the sudden increase in the concentration of methane (CH4) in the atmosphere in 2020, despite the isolation measures introduced due to the Covid-19 pandemic, reports Agerpres.

The slowdown in economic activity has indeed led to a reduction in methane emissions associated with the fossil fuel industry.

In a study published in the journal Nature, led by Professor Shushi Peng of Peking University, an international team of scientists revealed the key to the puzzle, which is explained by two phenomena.

Paradox

The first factor is represented by the lower presence in 2020 of the hydroxyl radical (OH), the main responsible for removing methane in the atmosphere.

These hydroxyl radicals, present in small quantities and with a lifetime of less than a second, are “the Pacman of the atmosphere: as soon as they detect something, they eat it and disappear,” explained French researcher Philippe Sieu of the Commissariat. de Energie Atomic and Alternative Energies (CEA), which conducted research at the Laboratory for Climate and Environmental Sciences (LSCE).

But these scavenging OH are linked to emissions of nitrogen oxide (NOx), a pollutant that is mainly a result of the transport sector, whose emissions have been reduced during isolation. Therefore, the researchers discovered a paradox: when pollution decreases, the concentration of methane increases.

Wet areas

The second identified factor is related to the increase in natural emissions of methane from the marshes. Microorganisms present in swamps or peatlands naturally produce this gas.

These areas are “very sensitive to climate,” said Mariel Sonois of the LSCE. “Microorganisms will produce more methane in warmer, wetter climates.”

In 2020, wetter and warmer conditions in northern latitudes and in the Northern Hemisphere tropics explain the higher methane production, the researchers estimate.

Vicious circle

Thus, the lessons of 2020 have very important implications for the climate: they signal a possible “packaging” of climate warming, which in turn could cause more harmful emissions, fueling a vicious cycle.

The study also points to the paradoxical effect of reducing pollution. “When we reduce NOx emissions by about 20%, the amount of methane can increase twice as fast, and we were very surprised by this,” noted Philippe Siais.

Therefore, emission control programs risk increasing the amount of methane in the future. “So if we’re going to meet the goals of the Paris Agreement, we’re going to have to move faster and faster to reduce methane sources,” he added.

Methane is the target of special attention in the fight against climate change because, even though it has a much shorter lifetime in the atmosphere (about ten years) than CO2, its heating capacity is much higher. This gas is responsible for about a third of global warming since the Industrial Revolution.

Its emissions are mainly related (60%) to human activities, which can therefore be influenced: industry using fossil fuels, agriculture, livestock, waste… The rest comes from wetlands.