The world breathed a collective sigh of relief as COVID-19 ravaged the globe, causing widespread lockdowns and plummeting emissions. Satellite sensors captured the dramatic decline in nitrogen dioxide levels, a telltale sign that industry and travel had come to a near standstill. For the first time in decades, the air seemed cleaner.
But amidst the pandemic-induced respite, a disturbing trend emerged: methane emissions surged to record highs. The second most significant greenhouse gas after carbon dioxide, methane's growth rate soared by 16.2 parts per billion in 2020 – a jump not seen since systematic records began in the early 1980s.
Researchers have long known that atmospheric methane doesn't simply vanish; it undergoes a complex chemistry that involves the hydroxyl radical, a highly reactive molecule that breaks down methane into water vapor and carbon dioxide. However, when nitrogen oxide levels plummeted during lockdowns, the production of this radical slowed to a crawl. Without enough hydroxyl radicals to go around, methane molecules lingered in the atmosphere for longer – allowing the potent greenhouse gas to warm the planet.
A new study published in Science sheds light on the tangled web of factors driving this phenomenon. The results suggest that while the weakened atmospheric sink explained the bulk of the 2020 surge, it wasn't the only factor at play. Tropical African and Asian wetlands alone were responsible for roughly 30 percent of the global methane emissions increase during the 2020-2022 period.
The surge was triggered by La Niña, a relatively rare meteorological event that led to record-breaking rainfall in the tropics. In these waterlogged environments, microbial methanogens thrived, churning out methane at an accelerated pace. The findings highlight the complex interplay between human activities and natural processes – a reminder that solving the methane problem won't be as simple as turning off infrastructure leaks.
As policymakers grapple with the implications of this study, they'll face two major challenges: climate feedbacks and the clean air paradox. Climate feedbacks refer to the unintended consequences of warming temperatures on natural systems; in this case, it may lead to an increase in biogenic methane emissions that we cannot simply turn off. The clean air paradox arises from the fact that improved urban air quality – a byproduct of reducing fossil fuel use – will also decrease the atmosphere's capacity to scrub methane.
Peng and his team emphasize that while reduced anthropogenic methane emissions are necessary, they may not be enough on their own. "I think that's the only choice for policymakers," he says. In reality, we'll need even more aggressive reductions than previously thought – a daunting task in an increasingly complex climate landscape.
The COVID-19 pandemic may have slowed human activity, but it has also highlighted the intricate web of relationships between human emissions and natural systems. As we move forward, it's crucial that policymakers recognize these connections and work towards a comprehensive solution that addresses both human activities and climate feedbacks – before the clean air paradox turns into a ticking time bomb.
But amidst the pandemic-induced respite, a disturbing trend emerged: methane emissions surged to record highs. The second most significant greenhouse gas after carbon dioxide, methane's growth rate soared by 16.2 parts per billion in 2020 – a jump not seen since systematic records began in the early 1980s.
Researchers have long known that atmospheric methane doesn't simply vanish; it undergoes a complex chemistry that involves the hydroxyl radical, a highly reactive molecule that breaks down methane into water vapor and carbon dioxide. However, when nitrogen oxide levels plummeted during lockdowns, the production of this radical slowed to a crawl. Without enough hydroxyl radicals to go around, methane molecules lingered in the atmosphere for longer – allowing the potent greenhouse gas to warm the planet.
A new study published in Science sheds light on the tangled web of factors driving this phenomenon. The results suggest that while the weakened atmospheric sink explained the bulk of the 2020 surge, it wasn't the only factor at play. Tropical African and Asian wetlands alone were responsible for roughly 30 percent of the global methane emissions increase during the 2020-2022 period.
The surge was triggered by La Niña, a relatively rare meteorological event that led to record-breaking rainfall in the tropics. In these waterlogged environments, microbial methanogens thrived, churning out methane at an accelerated pace. The findings highlight the complex interplay between human activities and natural processes – a reminder that solving the methane problem won't be as simple as turning off infrastructure leaks.
As policymakers grapple with the implications of this study, they'll face two major challenges: climate feedbacks and the clean air paradox. Climate feedbacks refer to the unintended consequences of warming temperatures on natural systems; in this case, it may lead to an increase in biogenic methane emissions that we cannot simply turn off. The clean air paradox arises from the fact that improved urban air quality – a byproduct of reducing fossil fuel use – will also decrease the atmosphere's capacity to scrub methane.
Peng and his team emphasize that while reduced anthropogenic methane emissions are necessary, they may not be enough on their own. "I think that's the only choice for policymakers," he says. In reality, we'll need even more aggressive reductions than previously thought – a daunting task in an increasingly complex climate landscape.
The COVID-19 pandemic may have slowed human activity, but it has also highlighted the intricate web of relationships between human emissions and natural systems. As we move forward, it's crucial that policymakers recognize these connections and work towards a comprehensive solution that addresses both human activities and climate feedbacks – before the clean air paradox turns into a ticking time bomb.