American scientists have found that the presence of microplastics is affecting cloud formation, impacting Earth’s weather and climate.
Clouds form when water vapor, an invisible gas in the atmosphere, attaches to small floating particles like dust and transforms into liquid water droplets or ice crystals. A recent study by a team of scientists from the University of Chicago has shown that microplastics can create ice crystals at temperatures 5 to 10 degrees Celsius higher than droplets of water without microplastics.
Earth continuously receives energy from the Sun, which is then reflected back into space, with clouds playing a role in warming and cooling during this process. (Photo: NOAA)
This indicates that microplastics in the atmosphere can influence weather and climate by facilitating cloud formation under conditions where they typically do not form.
Atmospheric chemists study how different types of particles form ice when they come into contact with liquid water. This ongoing process in the atmosphere is known as nucleation.
To determine whether microplastic fragments can act as nuclei for water droplets, scientists tested four of the most common plastics found in the atmosphere: low-density polyethylene, polypropylene, polyvinyl chloride, and polyethylene terephthalate. Each type was tested in both its pristine state and after exposure to ultraviolet light, ozone, and acid. All these substances are present in the atmosphere and can affect the composition of microplastics.
The researchers suspended microplastic particles in small water droplets and gradually cooled the droplets to observe when they froze. They also analyzed the surfaces of the plastic fragments to determine their molecular structure, as ice nucleation can depend on the chemical properties of the microplastic surface.
For most of the plastics studied, 50% of the water droplets froze at -22 degrees Celsius. These results are consistent with another recent study by Canadian scientists, who also found that some types of microplastics nucleate ice at warmer temperatures compared to droplets without microplastics.
Exposure to ultraviolet light, ozone, and acid tends to reduce ice nucleation activity on the particles. This suggests that ice nucleation is highly sensitive to small chemical changes on the surface of microplastics. However, these types of plastics still facilitate ice nucleation, meaning they can still influence the amount of ice in clouds.
According to the research team, to better understand how microplastics affect weather and climate, it is necessary to know their concentrations at altitudes where clouds form. Additionally, it is important to understand the concentration of microplastics compared to other particles that can nucleate ice, such as mineral dust and biological particles, to see if microplastics are present at comparable levels. These measurements will allow us to model the impact of microplastics on cloud formation.
