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 – and now they know why.
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.
At the heart of the story are hydroxyl radicals – the atmosphere’s ‘detergent’ that normally breaks down methane. They declined globally during this period because reduced human activity lowered the chemicals needed to form them, allowing methane to persist longer in the air. This chemical slowdown coincided an extended La Niña phase from 2020 to 2023 that brought wetter-than-average conditions across much of the Tropics and this provided ideal conditions for methane-producing microbes, boosting emissions from wetlands and inland waters.
Read full story: The curious case of why methane spiked around Covid