A new international study led by researchers at the Indian Institute of Technology Madras (IIT Madras) has revealed compelling evidence that human activity plays a pivotal role in shaping the behaviour of aerosols—tiny particles suspended in the atmosphere—directly influencing cloud formation and climate predictions.

Published in the prestigious ACS ES&T Air journal, the study was conducted between March and July 2020, a period that spanned the COVID-19 lockdown and subsequent easing of restrictions. Researchers closely monitored cloud condensation nuclei (CCN)—the aerosol particles responsible for cloud formation—along India’s coastal regions.

The findings show that as human-caused emissions rebounded following the lockdown, CCN concentrations increased dramatically by 80 to 250 percent. This spike was attributed to a process known as new particle formation (NPF), in which atmospheric gases undergo chemical transformation into aerosol particles.

“Our observations show clear evidence that anthropogenic emissions strongly influence aerosol behaviour and cloud formation,” said Professor Sachin S. Gunthe, the study’s lead author and faculty member at IIT Madras. “These findings could significantly reduce the uncertainty in climate models related to aerosol-cloud interactions.”

One of the most striking conclusions of the study is the role of anthropogenic organic matter in the growth of aerosol particles. Traditionally, organic aerosols were thought to inhibit cloud formation due to their lower efficiency in attracting water compared to inorganic particles. However, the new research suggests that when present in large numbers, these organic particles actually promote cloud formation.

This discovery challenges long-held assumptions and provides fresh insights into the complex interactions between human emissions, atmospheric chemistry, and climate systems.

The study arrives at a critical time, as the scientific community continues to grapple with one of the greatest uncertainties in climate modeling—understanding how aerosols interact with clouds and affect global climate patterns.

The research team included collaborators from multiple international institutions and highlights the growing importance of interdisciplinary global efforts to tackle the climate crisis.