Researchers from the Max Planck Institute of Chemistry identified methane concentrations in the Amazon that significantly exceed the estimates provided by climate and Earth system models. In certain areas of wetlands, recorded emissions reached up to four times the value calculated by the models. These findings were published in the journal Geophysical Research Letters in July 2026.
Details of the Research and Data Collection
Linda Ort, an atmospheric chemist and lead author, led the international study. The team dedicated two months, spanning from December 2022 to January 2023, to collect data. This period is notable for coinciding with the transition between the dry and rainy seasons in the region, a time when biomass burning generally does not occur, minimizing the impact of human activities on measurements.
Although methane emissions tend to be higher during the rainy season and lower in the dry season, the two months of collection represent an approximation of the annual average emissions from wetlands.
Results of Atmospheric Measurements
During the collection period, the background level of methane in the atmosphere was around 1.907 parts per billion (ppb). Since then, this value has shown an increase. On average, the methane levels measured above this atmospheric background were about twice as high as the values predicted by the models.
It was observed that the difference between measured and modeled data increases as altitude decreases. However, at altitudes of six kilometers or more, the data align well with the models, which Ort attributes to the efficient mixing of methane in the atmosphere at those heights, allowing the models to correctly represent air mass transport. At levels closer to the surface, however, the models show failures.
Variations by Wetland Type
By analyzing different types of wetlands, scientists found higher emissions: 26% more in river deltas, 19% more in reservoirs, and 13% more in frequently flooded river areas, compared to previous projections.
Analysis Methodology
Measurements were taken using sensors installed on the HALO research aircraft, which operated at altitudes ranging from 200 meters above the tree canopy to over 14 kilometers. At more than seven thousand measurement points, a specific absorption spectrometer for HALO was used, designed to detect methane accurately even under low atmospheric pressures found at high altitudes.
For the analysis, the Amazonian area was segmented into grid cells of 0.1 degree by 0.1 degree, which constitutes a high resolution for emission mapping. To correlate the methane measured in the air with its sources on the ground, the team applied an atmospheric transport model to track air masses to the corresponding grid cell. Subsequently, a NASA ensemble model was used to estimate the wetlands, complemented by a complex numerical method to calculate the actual amounts of methane release.
Limitations and Need for More Data
A factor contributing to the data limitation in the region is the persistence of cloud cover, which hinders satellite observations, coupled with the low frequency of terrestrial measurements in the tropics. Ort told Phys.org that the results indicate the existence of numerous underestimated methane sources in tropical wetlands, such as the Amazon rainforest, emphasizing the need for more data to refine these points and improve climate and Earth system models.
Eric Kort, director of the Department of Atmospheric Chemistry at the Max Planck Institute of Chemistry and co-author of the study, endorsed this assessment, stating that to determine the global methane balance reliably, more measurements are needed, not only in the Amazon but also in other tropical regions with little information, such as Central Africa and Southeast Asia.
Global Context of Methane
Methane is a potent greenhouse gas whose atmospheric concentration has increased drastically in recent decades. Approximately 65% of global emissions originate from anthropogenic sources, coming from sectors such as agriculture, fossil fuel production and consumption, and waste management. The remaining 35% comes from natural processes.
This gas is generated in large volumes by the decomposition of organic matter, such as dead leaves and plants, carried out by aquatic microorganisms. Wetlands represent the main natural source of methane to the atmosphere, as do reservoirs, where the flooding of large forest areas for hydroelectric power causes methane release through the decomposition of submerged organic matter. Despite this, there are still major doubts about the total volume of methane coming from wetlands and how these emissions might intensify in response to climate change.
