Clouds form when water vapor - an invisible gas in the atmosphere - sticks to tiny floating particles, such as dust, and turns into liquid water droplets or ice crystals. In a newly published study, we show that microplastic particles can have the same effects, producing ice crystals at temperatures 5 to 10 degrees Celsius (9 to 18 degrees Fahrenheit) warmer than droplets without microplastics. This suggests that microplastics in the air may affect weather and climate by producing clouds in conditions where they would not form otherwise.
We are atmospheric chemists who study how different types of particles form ice when they come into contact with liquid water. This process, which occurs constantly in the atmosphere, is called nucleation. Clouds in the atmosphere can be made up of liquid water droplets, ice particles or a mixture of the two. In clouds in the mid- to upper atmosphere where temperatures are between 32 and minus 36 F (0 to minus 38 C), ice crystals normally form around mineral dust particles from dry soils or biological particles, such as pollen or bacteria.
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Many cloud tops in nontropical zones around the world extend high enough into the atmosphere that cold air causes some of their moisture to freeze. Then, once ice forms, it draws water vapor from the liquid droplets around it, and the crystals grow heavy enough to fall. If ice doesn't develop, clouds tend to evaporate rather than causing rain or snowfall.
While children learn in grade school that water freezes at 32 F (0 C), that's not always true. Without something to nucleate onto, such as dust particles, water can be supercooled to temperatures as low as minus 36 F (minus 38 C) before it freezes. For freezing to occur at warmer temperatures, some kind of material that won't dissolve in water needs to be present in the droplet. This particle provides a surface where the first ice crystal can form. If microplastics are present, they could cause ice crystals to form, potentially increasing rain or snowfall.
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https://theconversation.com/microplastics-promote-cloud-formation-with-likely-effects-on-weather-and-climate-240192