The impact of microplastics on heavy rainfall 🌧️

As they accumulate in the atmosphere, microplastics could influence weather and climate, as suggested by a recent study published in Environmental Science & Technology: Air.

Their presence promotes the formation of ice crystals, which are essential for the formation of clouds and precipitation. Microplastics may therefore play a novel role in climate processes.


These tiny fragments, often smaller than 100 micrometers, travel with the wind and reach surprising heights. They have been found in mountain clouds in Asia. These data demonstrate their systematic infiltration into atmospheric processes.

Their ability to induce ice crystal formation relies on a phenomenon known as nucleation. Typically, pure water only freezes at extremely low temperatures, but the presence of solid particles like dust or bacteria raises this threshold. According to the study, microplastics make crystallization possible at just -7.6°F (-22°C), much "warmer" compared to the -36.4°F (-38°C) required otherwise.

These crystals play a crucial role in cloud dynamics by altering their structure and behavior. By promoting cloud growth, they increase the likelihood of heavy precipitation.

In practical terms, these crystals act as condensation nuclei: water droplets present in the atmosphere form around these solid particles, allowing a larger amount of water vapor to cling to them. As the droplets grow and clump together, they eventually become heavy enough to overcome the updrafts that had kept them suspended within the cloud.

This accelerated coalescence process results in larger drops, which then fall as rain, often more abundant and intense than normal.


Clouds also play a key role in regulating the Earth's temperature. Their composition, combining liquid water and ice, determines their ability to reflect or absorb sunlight. By altering this balance, microplastics could disrupt the planet's energy balance, amplifying certain climatic effects.

The study examined four common types of plastics, such as polypropylene and PVC, and simulated their "aging" in the atmosphere. When exposed to ozone or UV rays, some plastics see their nucleation ability change, making their climate effects harder to predict.

Nonetheless, many unknowns remain. What is the actual concentration of microplastics in clouds? How do they compare to other atmospheric particles? These are some of the questions scientists hope to answer to better understand these invisible but influential climate agents.

Why do clouds need solid particles?

Clouds do not form solely from water vapor. Solid particles like dust or crystals serve as nuclei around which moisture can condense. These nuclei, known as condensation nuclei, reduce the energy needed to transform moisture into water droplets. Without them, clouds would have a hard time forming.

The size and composition of these particles directly influence cloud dynamics. Some particles promote larger droplets, while others limit their growth. The abundance of these particles, often caused by human or natural activities, alters cloud structure and their ability to produce precipitation.