Earth’s atmosphere photographed from space.
At the beginning of the decade, one of the most important greenhouse gases in the Earth’s atmosphere, methane (CH4), surged in volume, puzzling the global science community. Debates began on what the culprit was for this unexpected spike, making it a concerning topic of international discussion and further research. An Auburn University professor at the College of Forestry, Wildlife and Environment (CFWE) who participated in the worldwide study found that this flux in greenhouse gases occurred beyond the control of human intervention.
Atmospheric methane is naturally broken down in the atmosphere by reactions with hydroxyl radicals (OH) formed by ultraviolet radiation. These radicals act as a ‘detergent,’ cleansing the excess methane and regulating its levels. This relationship between the radicals and CH4 supports a more balanced atmospheric methane concentration, protecting the Earth and its life from climate warming. However, this balance was altered when, in 2020, it was found that methane, the second most important greenhouse gas just behind carbon dioxide, reached a peak increase of 16.2 parts per billion (ppb) per year and progressively dipped to an increase of 8.6 ppb per year by the end of 2023.
Amid the COVID-19 pandemic, the Earth’s atmosphere experienced a dramatic slowdown in the emission of global air pollution. Fewer people were driving cars, and some industries scaled back production or stopped completely. The reduction of OH produced by these activities, which acts as the CH4 or methane cleanser, pushed atmospheric methane to increase during this period.
While this atmospheric chemistry shift was occurring above, back on Earth, other influences were contributing to this change. Meteorologically, the planet was also undergoing an extensive La Niña, making the climate wetter. This pattern brought heavier-than-normal precipitation, particularly in the tropic regions, flooding landscapes and creating more wetlands. These water systems hosted an influx of microbes that naturally produce methane. Some of the most affected areas included tropical Africa, Southeast Asia and arctic regions with warmer soils.
Zutao Ouyang, a CFWE assistant professor of ecosystem modeling, contributed geospatial science expertise to this project titled “Why methane surged in the atmosphere during the early 2020s,” recently published in Science, one of the world’s top peer-reviewed academic journals. His expertise in artificial intelligence (AI) models revolutionized the study by providing new, innovative ways to monitor global methane emissions.
“We trained an AI model using a large field-observed emissions dataset to simulate how much methane is emitted from rice paddies,” Ouyang said. “This bottom-up estimate based on source emissions helps cross-validate sources inferred from top-down estimates derived from atmospheric measurements of methane concentrations, enabling us to arrive at the source of the likely origins.”
The findings within the study, co-led by Ouyang, also pointed to a need for better data-farming tools, especially in remote and rapidly changing environments. Using the geospatial model created by Ouyang for monitoring methane emissions from rice agriculture, the research team was able to extract key data that explained the increased methane emissions experienced between 2020 and 2023.
“Both our AI models and others consistently show higher rice paddy emissions during 2020-2023 relative to 2019, strengthening our conclusion that rice production also contributes to the surge of CH4 during this period, beyond the reduction that would be expected from changes in the atmospheric cleansing processes,” Ouyang said.
The necessity of cutting-edge data tools is at the forefront of today’s scientific community. Auburn faculty such as Ouyang serve as an invaluable resource to the global science stage, creating the necessary tools for solving, quite literally, the world’s issues.
“These next-generation geo-spatial emission models will integrate earth foundation models and physical constraints to conduct near-real-time monitoring of greenhouse gas emissions,” Ouyang said. “We will be providing more timely and actionable information for policymakers and environmental management professionals.”
