Research challenges long-held assumptions on organic aerosols and provides critical empirical data to refine global climate predictions
A landmark international study led by the Indian Institute of Technology Madras (IIT Madras) has highlighted the significant role of human activity in influencing aerosols—tiny suspended particles in the atmosphere crucial for cloud formation and rainfall.
The findings, published in the American Chemical Society’s ES&T Air Journal, provide vital empirical data that could help reduce uncertainties in global climate models, long considered one of the most complex areas in climate science.
The study, conducted along India’s coastal regions between March and July 2020, found a startling 80–250% surge in cloud condensation nuclei (CCN) following the COVID-19 lockdown.
This increase, researchers said, was driven by new particle formation as human-caused emissions rebounded after the lockdown. The results underscore how quickly atmospheric conditions respond to human behavior.
“Our research reveals that anthropogenic emissions strongly influence aerosol behaviour, particularly in how they form clouds. These findings challenge existing models and propose new avenues for understanding how human activities shape climate patterns,” said Prof. Sachin S. Gunthe, lead researcher and Coordinator, Center for Atmospheric and Climate Sciences, IIT Madras.
One of the most groundbreaking insights from the study is that organic aerosols—previously thought to hinder cloud formation—can actually enhance it under certain conditions.
Researchers observed that despite their lower ability to attract water compared to inorganic particles, the sheer number of organic particles in the atmosphere enabled them to significantly contribute to cloud development.
This challenges a long-standing scientific belief and highlights the complexity of aerosol-cloud interactions, which remain a major source of uncertainty in climate predictions.
Key Findings of the Study:
- Human activities significantly increase CCN concentrations, altering cloud formation.
- Organic aerosols, contrary to traditional assumptions, can promote cloud development.
- Post-lockdown conditions provided a “natural experiment” revealing the sensitivity of clean atmospheres to new emissions.
- Real-world measurements offer crucial clarity that computer-based simulations alone cannot achieve.
Dr. M. Ravichandran, Secretary, Ministry of Earth Sciences, Government of India—who was not involved in the research—praised the study, stating:
“Aerosol-cloud interactions are intrinsically complicated, and these findings underscore that human activities can dramatically influence underlying processes. This is critical information for negotiating future atmospheric dynamics.”
The research team included national and international collaborators such as Aishwarya Singh, a former IIT Madras PhD scholar now at the Max Planck Institute for Chemistry in Germany, and Prof. R. Ravikrishna of IIT Madras.
Singh emphasized the importance of the lockdown observations:
“We witnessed firsthand how a cleaner atmosphere can be highly sensitive to new emissions, significantly altering aerosol-cloud interactions. This has profound implications for future climate predictions.”
The researchers stress that climate science must adopt a dual approach—using advanced simulations while grounding them in empirical data. By blending these methods, they believe climate projections will become more reliable, aiding global efforts to mitigate climate change.
Prof. Ravikrishna summed it up:
“We cannot predict the future of our climate without rigorously understanding the current state of our environment. Measurements provide an essential context to refine and enhance climate models.”
The study not only advances scientific understanding but also serves as a reminder of the deep impact of human activity on climate systems. It paves the way for more accurate models that can guide environmental policy and sustainable practices worldwide.