Their impact is still small, but could become greater in the coming years as the concentration in the atmosphere increases.

All kinds of small dust or liquid particles float in the air. For example, think of clouds and fog, but also soot particles from traffic. These aerosols then influence our climate by absorbing or reflecting incident radiation from the sun. Meanwhile, the amount of microplastics in our atmosphere is also increasing. And so researchers asked themselves a new study wonder whether these polluting plastics also affect our climate.

Aerosols

In recent years, numerous researchers have told us that microplastics are present in the air we breathe. However, little is known about how these microplastics behave in the atmosphere. We do know that about other types of fabrics. “Aerosols actually behave like little disco balls,” explains researcher Laura Revell. “That means they reflect sunlight back into space. This then has a cooling effect on the earth. Most types of aerosols in the atmosphere reflect light, so aerosols in general have partially offset the warming caused by greenhouse gases in recent decades. Soot (or black carbon) is an exception, because it absorbs sunlight and thus has a warming effect.”

microplastics

In the new study, the researchers decided to map the impact of microplastics on our climate. Because do they reflect sunlight – which has a cooling effect – or do they absorb sunlight – which has a warming effect? “In the study, we examined how microplastic fragments and fibers – two types of microplastics commonly found in the atmosphere – interact with light,” Revell said. “We then fed this information into a global climate model to calculate the overall impact of microplastics in the air on Earth’s climate.”

What are microplastics?
Microplastics are small (often microscopic) pieces of plastic, which are in any case no larger than 5 millimeters. They arise when they are intentionally produced in that size, or when larger pieces of plastic are broken down into smaller and smaller pieces. Microplastics are in all kinds of products, including clothing and cosmetics. Because they are hardly broken down in the environment, they in principle never disappear and they end up in our own drinking water and food. For example, microplastics have already been found in various foods, including honey, milk, beer and seafood. But they are also in the air and are transported across the earth by the wind. That is why we find microplastics in the atmosphere above urban areas as well as in remote, less populated regions.

The researchers discovered that microplastics actually have both a cooling and a warming effect. “In general, microplastics reflect sunlight,” Revell says. “However, they can also absorb the radiation emitted by the Earth. And that means they contribute very little to the greenhouse effect.”

Small

At the moment, the impact of microplastics on our climate is still small. But that may not last. “Their impact is expected to increase in the future,” Revell said. “At present, an estimated five billion tons of plastic waste have accumulated in landfills and in the environment. But in the next three decades, this figure may triple. Because plastic breaks down with age and exposure to light, creating microplastics, we expect these tiny pieces of plastic to remain in the Earth’s atmosphere for many years to come.” And that means that as the concentration of microplastics in the atmosphere increases, their impact on the climate threatens to become a lot bigger in the coming years.

climate

If the global average concentration increases to values ​​already detected in some megacities, the effect of microplastics in the air on the climate will be significant, according to the researchers. “It may be similar to other atmospheric aerosols that are regularly included in climate models,” Revell predicts.

Overall, the researchers conclude that mismanaged plastic waste could have a stronger impact on our climate in the future. Moreover, they suspect that microplastics already contribute locally to atmospheric heating or cooling. “Unless we take serious action to address microplastic pollution, plastic production and waste management, microplastics in nature will continue to increase and contribute to future climate change,” Revell concludes.