What is it about?
Our study investigates how ammonia (NH₃) emissions from human activities—mainly agriculture—affect aerosol formation high in the atmosphere, in the upper troposphere and lower stratosphere. Using the EMAC Earth system model and experimental data from CERN CLOUD project, we show that NH₃ transported upward by convection can significantly enhance the formation of new particles. These particles grow to become cloud condensation nuclei (CCN), which seed clouds. Our results reveal that anthropogenic NH₃ can double particle numbers and increase CCN concentrations in the upper atmosphere by up to 2.5 times, and boost aerosol optical depth (AOD) by as much as 80%, indicating strong impacts on clouds and climate.
Featured Image
Photo by Randy Fath on Unsplash
Why is it important?
Ammonia emissions are expected to rise throughout the century due to global agricultural intensification. While the role of NH₃ in surface air pollution is well known, its influence higher in the atmosphere has been largely overlooked. Our study shows that these emissions affect not only air quality but also the aerosol–cloud interactions in the upper troposphere. Including NH₃-driven upper-tropospheric aerosol formation in climate models will improve predictions of cloud properties, radiative forcing, and climate change. These insights are timely for designing air quality and agricultural policies that also consider their broader climate implications.
Perspectives
As lead author, I was fascinated by how something as common as agricultural ammonia could reach the upper atmosphere and change global aerosol behavior. Working with the CLOUD team and the EMAC Earth system model revealed a hidden climate pathway connecting farming practices to high-altitude aerosol formation. This work highlights the need for interdisciplinary approaches—linking atmospheric chemistry, satellite observations, and climate modeling—to fully understand human influence on the atmosphere from the ground to the upper troposphere.
Christos Xenofontos
Cyprus Institute
Read the Original
This page is a summary of: Global impact of anthropogenic NH
3
emissions on upper tropospheric aerosol formation, Proceedings of the National Academy of Sciences, October 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2506658122.
You can read the full text:
Contributors
The following have contributed to this page
