ERC grant helps to quantify the impact of anthropogenic air pollution particles on climate

Estonian Research Council

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Velle Toll, Associate Professor in Climate Physics at the University of Tartu

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Credit: The author of the photo is Andres Tennus

University of Tartu Associate Professor in Climate Physics Velle Toll received the Consolidator Grant from the European Research Council (ERC) to quantify the extent to which air pollution particles cool the Earth’s climate. The results of Toll’s work would help fill a gap in our detailed understanding of human-induced climate change and improve the accuracy of climate projections. 

The main cause of anthropogenic climate change is the greenhouse gases released by burning fossil fuels, and the magnitude of their warming effect has been accurately quantified. However, burning fossil fuels also emits large quantities of air pollution particles (aerosols), which act as cloud condensation nuclei, influence cloud properties, and cool the Earth’s climate. Unfortunately, it remains unclear to what extent these particles cool the climate, leaving a gap in current physical understanding. 

According to Toll, reducing air pollution is essential to save lives. Yet, when the air is cleaned of these particles, global warming can speed up because the cooling effect of anthropogenic air pollution particles diminishes, while emissions of anthropogenic greenhouse gases that cause warming continue to rise.  

“It is necessary to close this gap in our current knowledge. If we get confirmation that the cooling effect of air pollution particles on the climate is greater than previously thought, it would mean that the Earth’s climate is more sensitive to anthropogenic greenhouse gases than we currently know. Therefore, reducing the emissions of air pollution particles speeds up global warming, and each tonne of greenhouse gases released into the atmosphere warms the climate more than we now assume,” explained Toll. 

Factory chimney as a laboratory 

One reason why the climate impact of anthropogenic air pollution particles are relatively poorly quantified is that, until recently, researchers lacked reliable methods to distinguish the effect of pollution particles on clouds from the impact of natural variability of weather conditions. Velle Toll’s research, which compares the properties of clouds near large factories with those of nearby unpolluted clouds, has led to a breakthrough. Toll’s approach is analogous to a controlled experiment, but laboratory-like conditions arise naturally around factory chimneys without any intervention by the researcher. 

In their previous studies, using factory chimneys as real-world laboratories, Toll’s team analysed hundreds of polluted cloud regions near large factories. In the new project, Toll plans to expand the research to millions of cases by modelling the wind-driven spread of air pollution and applying machine learning. To achieve this, the team uses public databases on industrial sites and ship movements and compares the physical properties of polluted and unpolluted clouds based on satellite data. A global analysis will enable to assess whether anthropogenic air pollution particles have reduced the warming effect of greenhouse gases more than previously assumed. 

Velle Toll’s research project “Tracking Polluted Clouds: the Plausibility of a Strong Aerosol Cooling Effect on Earth’s Climate” lasts for five years, and its budget is nearly two million euros. In the latest call for proposals for the European Research Council’s Consolidator Grant, 3,121 proposals were submitted, and 349 projects from 25 countries received funding.