Understanding the Methane Surge During COVID-19
During this global freeze due to the COVID-19 pandemic, researchers observed something quite interesting – a very sudden increase in atmospheric methane emissions. The greenhouse gas methane is so active that it can actually play a pivotal role in affecting the global climate; thus, sources of methane will become highly influential in lowering the effects of this gas.
Between 2020 and 2022, methane emissions suddenly spiked, causing speculation about the reason behind the spurt. New study led by Zhen Qu, assistant professor at North Carolina State University, finally unmasks the mystery. Analyzing satellite data and atmospheric simulations, it has been established that increased methane emissions during that period were driven mainly by inundation of tropical wetlands along with a slight decrease in atmospheric hydroxide (OH) levels.
What Caused the Methane Surge?
The context needs to be set before diving into findings. Why was this an unexpected rise in methane? Methane, in its atmospheric levels, had grown regularly between 2010 and 2019, from 499 Tg to 550 Tg. But between 2020 to 2022, it almost sharply shot up to 570-590 Tg. This made a huge slowdown in industrial and transportation activities across the world so that many were expecting its reduction instead of growth in the case of green house gas emissions.
One hypothesis was that the decline in anthropogenic air pollution led to a decline in hydroxyl radicals (OH), which degraded methane in the atmosphere. There would, therefore be a fewer supply of OH, implying that methane molecules stayed longer in the atmosphere. This indeed was true, but not the main cause.
Role of Wetlands in Methane Production
Methane is produced in wetlands through a process called anaerobic microbial activity, where microbes break down organic matter in areas that have very little oxygen in them. It enriches the process when wetlands become more waterlogged, providing ideal conditions for the production of methane.
It was found by the scientists led by Qu that greater flooding and the storage of water in tropical wetlands are particularly responsible for the surge of methane during 2020-2022 in equatorial regions of Asia and Africa. The authors noted that the increase in methane emission was mainly of these regions origin – 43 and 30%, respectively. Probably more flooding was caused by heavy precipitation associated with La Niña conditions during this period, which increased the activities of microbes and further enhanced the emission of methane.
More detailed information on wetland methane emissions can be accessed through NASA’s Earth Observatory, with resources on the role of tropical wetlands in methane production.
Decline of Hydroxide and its Effect on Methane Levels
Although the basic cause of the rise in wetland methane emissions contributed to the rise, the scientists found that OH levels in the atmosphere had decreased as well. There are several roles these hydroxyl radicals have. One such role is to break up the methane molecules in the atmosphere and regulate levels of methane. The 28% rise in the methane level was due to the lowered OH concentrations due to reduced air pollution by the pandemic.
However, according to Qu, the wetland emissions were dominant. “Our results identify the wet tropics as the key drivers of the rise in methane concentrations since 2010,” he said.
For more on how hydroxyl radicals interact with methane and other gases in the atmosphere, visit NCAR’s Climate & Global Dynamics Laboratory.
Research Methodology: A Deep Dive into the Data
To obtain these results, Qu’s team simulated conditions of the atmosphere from 2010 through 2019 using satellite data and chemical transport models and overlaid these conditions onto those during the methane surge from 2020 through 2022. They simulated levels of both methane and OH, creating a model that let them pinpoint specific sources of methane emissions during the period.
According to their analysis, they found that the dominant role of tropical wetlands fueling the methane increase marks a call to understand precisely how climate patterns, including La Niña, drive wetland dynamics. Their research was published in the Proceedings of the National Academy of Sciences, titled \\”Inverse Modeling of 2010–2022 Satellite Observations Shows that Inundation of the Wet Tropics Drove the 2020–2022 Methane Surge.\\”
In order to access the full research, you can visit PNAS
Climate Change and Implications of Methane Surge
Increases in methane emissions during a pandemic shutdown have critical implications for climate change. Methane has 28 times the global warming potential of CO2 over a 100-year time frame, making it a very critical target area for emissions reductions. These observations caution that wetland dynamics, especially in tropical regions, should be monitored to predict and mitigate emissions better in the near future.
Heavy flooding in wetland and rice cultivation areas as a result of La Niña conditions, which prevailed during parts of the 2020-early 2023 period, is expected to continue influencing methane production. Understanding how precipitation influences methane emissions informs the development of effective climate strategies.
Wetlands, Methane, and the Future of Climate Mitigation
The study conducted by Zhen Qu and his co-authors has given better insights into the contributors to the tremendous increase in methane during the global COVID-19 lockdown. Although a decrease in atmospheric hydroxide was an insignificant contributor, it is the increased flooding of tropical wetlands that created a perfect scenario for the production of methane-producing microbes.
These remind us of the complexity with which natural systems interact and the role of greenhouse gases in climate patterns. As we forge ahead, it would be important to learn more about wetland ecosystems and how these respond to climate patterns, which will be key in developing strategies meant to mitigate methane’s impact on global warming.
Researchers, now better equipped than at any other time with advanced satellite technology and atmospheric simulations, are now well-positioned to detect the origin of methane and examine varied means toward decreasing atmospheric methane levels. To catch up on the latest research and ingenuity about reducing methane emissions, you may follow updates from the Proceedings of the National Academy of Sciences.
This project received funding through NASA’s Early Career Investigator Program and represents an important step toward one of the most pressing climate issues of our generation.
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