Microplastics trigger cloud formation and alter weather patterns 

Microplastics have been found in some of the world’s most remote environments, from the snow-capped peaks of Mount Everest to the ocean depths of the Mariana Trench, infiltrating ecosystems and even human bodies. 

Now, new research led by scientists at Pennsylvania State University (Penn State) reveals that these tiny plastic particles may also be affecting the atmosphere and climate. 

The study shows that microplastics can act as ice nucleating particles, potentially altering cloud formation, precipitation, and even global climate patterns.

Microplastics as ice nucleators

Microplastics – tiny plastic particles less than 5 millimeters in size – were found to act as ice nucleating particles, which are microscopic aerosols that allow ice crystals to form in clouds. 

“Throughout the past two decades of research into microplastics, scientists have been finding that they’re everywhere, so this is another piece of that puzzle,” said Miriam Freedman, a professor of chemistry at Penn State and senior author of the study. 

“It’s now clear that we need to have a better understanding of how they’re interacting with our climate system, because we’ve been able to show that the process of cloud formation can be triggered by microplastics.”

How the research was conducted

In their experiments, the researchers examined four types of microplastics: low-density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). 

By suspending each plastic in small water droplets and slowly cooling them, the team observed how these particles influenced ice formation. 

They found that droplets containing microplastics froze at temperatures between -22 and -28 degrees Celsius, much warmer than the typical -38 degrees Celsius required for droplets without defects to freeze.

“Any kind of defect in the water droplet, whether that’s dust, bacteria, or microplastics, can give ice something to form – or nucleate – around,” said study lead author Heidi Busse, a graduate student at Penn State.

Microplastics and weather patterns

The ability of microplastics to initiate ice formation in clouds could have widespread consequences for weather and climate. When clouds contain more ice, it can affect precipitation patterns, often leading to heavier rainfall events as water droplets are delayed in their descent until they reach a larger size. 

“In a polluted environment with many more aerosol particles, like microplastics, you are distributing the available water among many more aerosol particles, forming smaller droplets around each of those particles,” said Busse. 

“When you have more droplets, you get less rain, but because droplets only rain once they get large enough, you collect more total water in the cloud before the droplets are large enough to fall and, as a result, you get heavier rainfall when it comes.”

Microplastics and cloud structure

The influence of microplastics on cloud structure may also affect how much solar radiation is reflected back into space or retained in Earth’s atmosphere. 

Clouds at higher altitudes can help trap heat emitted from the Earth, which in some cases can contribute to warming. Freedman emphasized that the ratio of liquid water to ice within clouds plays a crucial role in determining whether clouds have a net cooling or warming effect. 

As microplastics accumulate in the atmosphere, their potential influence on mixed-phase clouds may mean they are already impacting global climate in ways that are not yet fully understood.

Changing behavior of aging microplastics

The researchers also investigated how “environmental aging” -the natural processes that particles undergo when exposed to sunlight, ozone, and other elements in the atmosphere – affects the ice-nucleating properties of microplastics. 

The analysis revealed that aging generally reduced the ice-forming ability of LDPE, PP, and PET, while PVC’s ice-forming potential actually increased due to changes on its surface caused by environmental aging. 

This variation suggests that over time, as microplastics are exposed to the atmosphere, their impact on cloud formation may change.

“We know that the fact that microplastics can nucleate ice has far-reaching effects; we’re just not quite sure yet what those are,” Busse said. 

“We can think about this on many different levels, not just in terms of more powerful storms but also through changes in light scattering, which could have a much larger impact on our climate.”

Future research on microplastic additives

Next, the team plans to study common additives found in plastics, such as plasticizers, to gain a more comprehensive understanding of how these substances might further influence atmospheric behavior. 

Many plastics contain a variety of additives that can affect their physical and chemical interactions within the environment. Analyzing these additional factors may reveal more about how microplastics in the atmosphere could influence weather and climate dynamics.

“We know the full lifecycle of these plastic items we use every day could be changing the physical and optical properties of the Earth’s clouds and, therefore, changing the climate in some way, but we still have a lot to learn about exactly what they are doing,” Busse said. 

As scientists continue to unravel the atmospheric behavior of microplastics, new findings may add to the growing list of impacts these particles have on global systems – from terrestrial and marine ecosystems to human health and now, potentially, the climate.

A growing area of concern 

Microplastics are a relatively new area of concern within atmospheric and climate science, and researchers like Freedman are now beginning to connect their widespread presence in the atmosphere to possible impacts on large-scale weather patterns and climate systems. 

The study highlights the importance of understanding the full life cycle and environmental behavior of plastics, especially as evidence mounts that microplastics influence processes fundamental to Earth’s climate. 

While much is still unknown, Freedman’s team hopes to advance climate models that incorporate microplastics, allowing scientists to better predict how these particles could alter the planet’s delicate atmospheric balance.

As studies like this continue, microplastics might not only reshape our understanding of environmental pollutants but also inform future regulations aimed at reducing their release and mitigating their long-term impacts.

The study is published in the journal Environmental Science and Technology: Air.

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