Impact of Air Pollution on Methane Budget: New International Study

An international research collaboration involving scientists from the Institute of Climate and Energy Systems – Stratosphere at Forschungszentrum Jülich in Germany has unveiled critical insights into how air pollutants such as carbon monoxide, ozone, and nitrogen oxides influence the natural breakdown of methane in the atmosphere. The study, published on May 28, 2025, in the renowned journal Nature, highlights the complex interplay between air quality and methane's atmospheric lifetime, emphasizing the importance of understanding these dynamics in the context of climate change.

Methane is recognized as one of the most potent greenhouse gases, contributing significantly to global warming. The atmosphere’s chemistry, particularly concerning methane, is intricately linked to the presence of hydroxyl radicals (OH), which are responsible for the removal of approximately 90% of methane in the lower atmosphere. According to Dr. Michaela Hegglin, a researcher at Forschungszentrum Jülich, "The atmosphere is a highly non-linear and complex chemical system. Even small changes in its composition can have a large impact on how long methane persists."

The researchers conducted a comprehensive analysis using atmospheric observations and modeling data to assess how varying levels of air pollutants from 2005 to 2021 have influenced hydroxyl concentrations. Their findings revealed that declining carbon monoxide emissions, attributed to advancements in cleaner combustion technologies, have enhanced methane breakdown. Simultaneously, increases in ozone and water vapor have also elevated OH levels, collectively strengthening the global methane sink by an estimated 1.3 to 2.0 teragrams per year—equivalent to a 10 to 20 percent increase.

However, the relationship between air quality and methane removal is not linear. Significant events, such as the COVID-19 pandemic and widespread wildfires, have been shown to cause dramatic fluctuations in OH levels. For instance, during the pandemic, nitrogen oxides emissions fell sharply due to reduced human activity, which led to lower ozone levels and consequently weakened the methane sink. This resulted in a faster accumulation of methane in the atmosphere.

The study emphasizes the critical link between air pollution and climate action. It suggests that while reducing ozone precursors can improve air quality, it may inadvertently slow methane removal, thereby complicating climate strategies. Researchers argue for a more integrated approach that considers the interactions between air quality and methane dynamics, particularly in tropical regions where ozone and water vapor significantly influence hydroxyl levels.

Climate change further complicates these dynamics, introducing opposing effects. Rising temperatures contribute to increased water vapor, which promotes methane breakdown, while intensified wildfires, exacerbated by climate change, elevate carbon monoxide emissions that inhibit OH levels and slow methane removal.

This research underscores the necessity for policymakers to adopt a comprehensive view of air quality management in the context of climate change mitigation. By acknowledging the interdependencies between air pollutants and greenhouse gases such as methane, effective strategies can be developed to address both environmental health and climate stability.

The findings of this study are foundational for future research and policy-making efforts aimed at reducing methane emissions and improving air quality, both of which are vital for sustainable climate action. As the global community grapples with the challenges posed by climate change, understanding the intricacies of atmospheric chemistry will play a crucial role in shaping effective environmental policies.