IIT-Madras study shows human activity can alter couds, shake up climate models

NEW DELHI: Human activity can change the very building blocks of clouds, with far-reaching consequences for rainfall and climate. An international study led by IIT-Madras has found that once the Covid-19 lockdown lifted in 2020, cloud-forming particles over coastal India shot up by as much as 250%, overturning long-held assumptions about aerosols and their role in climate change.Published in the American Chemical Society’s ES&T Air Journal, the study provides rare field evidence on how emissions shape aerosols — tiny particles suspended in the air that act as cloud seeds. The findings, scientists say, could help reduce uncertainties in global climate models that have so far relied heavily on computer simulations.“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 Professor Sachin S Gunthe, who led the study at IIT-Madras.Measurements taken in Chennai between March and July 2020 showed that during the lockdown, cleaner marine air dominated. Once restrictions eased, polluted continental air took over, sparking frequent “new particle formation” events.

These fresh particles, rich in organic matter, quickly grew into cloud condensation nuclei (CCN), boosting their concentrations by 80–250%.Contrary to earlier belief that organic aerosols hinder cloud growth, the study found that their sheer numbers can actually promote cloud formation. “The lockdown acted like a natural experiment, showing how sensitive the atmosphere is to sudden changes in human activity,” said co-author Aishwarya Singh, now with the Max Planck Institute for Chemistry.Dr M Ravichandran, Secretary, Ministry of Earth Sciences, who was not involved in the study, called the results “critical information for negotiating future atmospheric dynamics,” noting that the work highlights the complicated but crucial link between pollution and climate.With climate change debates hinging on accurate forecasts, the IIT Madras-led study underscores a simple but unsettling truth: the way we pollute—or clean—the air today could decide how clouds, rainfall, and even temperatures behave tomorrow.