It is estimated that up to 60 percent of methane in the atmosphere is the result of human activities; however, researchers have found it difficult to predict future trends due to both lack of measurements and incomplete understanding of carbon-climate feedbacks.
Now, researchers at NASA's Goddard Space Flight Center have combined a number of data sets—including domestic field campaigns and international satellites—with a computer model that accurately estimates methane emissions based on known processes for certain land-cover types, such as wetlands. The model also simulates the atmospheric chemistry that breaks down methane and removes it from the air.
"Methane is a gas that's produced under anaerobic conditions, so that means when there's no oxygen available, you'll likely find methane being produced," said Goddard research scientist Ben Poulter. “In addition to fossil fuel activities, primarily from the coal, oil and gas sectors, sources of methane also include the ocean, flooded soils in vegetated wetlands along rivers and lakes, agriculture, such as rice cultivation, and the stomachs of ruminant livestock, including cattle.”
Based on simulation results, the researchers then used a weather model to see how methane travels and behaves over time while in the atmosphere. The data visualization of their results shows methane's ethereal movements and illustrates its complexities both in space over various landscapes and with the seasons.
This 3D view led researchers to pinpoint global methane hotspots, including the Amazon River Basin, India and the Arctic. In South America, the Amazon River Basin and its adjacent wetlands flood seasonally, creating an oxygen-deprived environment that is a significant source of methane. In fact, about 60 percent of global methane emissions come from the tropics. In India, rice cultivation and livestock are the two driving sources of methane, including enteric fermentation—or the processing of food in the guts of cattle.
Like India, the Arctic and high-latitude regions are responsible for about 20 percent of global methane emissions.
“There's a massive amount of carbon that's stored in the northern high latitudes,” said research meteorologist Lesley Ott with the Global Modeling and Assimilation Office at Goddard. “One of the things scientists are really concerned about is whether or not, as the soils warm, more of that carbon could be released to the atmosphere. Right now, what you're seeing in this visualization is not very strong pulses of methane, but we're watching that very closely because we know that's a place that is changing rapidly and that could change dramatically over time.”
The new 3D model is the missing piece in the full methane puzzle. Previous data have revealed emission levels and atmospheric conditions separately, but this model helps researchers understand where methane is coming from and, most importantly, where it is going. Additionally, the model will help the planning of future field and satellite missions. Currently, NASA’s satellite GeoCarb is planned for a 2023 launch to provide geostationary space-based observations of methane in the atmosphere over much of the western hemisphere.
Photo credit: NASA/Scientific Visualization Studio