Direct radiative effects of airborne microplastics

• Published in: Nature (London) Vol. 598; no. 7881; pp. 462 - 467
• Main Authors: Revell, Laura E., Kuma, Peter, Le Ru, Eric C., Somerville, Walter R. C., Gaw, Sally
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.10.2021; Nature Publishing Group
• Subjects: 119/118; 639/766/400; 704/106/35; 704/106/694/1108; 704/172/169/895; Aerosol-cloud interactions; Aerosols; Airborne particulates; Airborne wastes; Atmosphere; Atmospheric aerosols; Boundary layers; Climate change; Contaminants; Cooling; Environmental aspects; Fourier transforms; General circulation models; Geographical distribution; Global climate; Humanities and Social Sciences; Microplastics; multidisciplinary; Optical properties; Particulate emissions; Particulate matter; Plastic pollution; Polyethylene; Radiation; Radiative forcing; Radiative transfer; Science; Science (multidisciplinary); Short wave radiation; Simulation; Spectrum analysis; Vertical distribution; New Zealand; Beijing China; China
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-021-03864-x

Microplastics are now recognized as widespread contaminants in the atmosphere, where, due to their small size and low density, they can be transported with winds around the Earth 1 – 25 . Atmospheric aerosols, such as mineral dust and other types of airborne particulate matter, influence Earth’s climate by absorbing and scattering radiation (direct radiative effects) and their impacts are commonly quantified with the effective radiative forcing (ERF) metric 26 . However, the radiative effects of airborne microplastics and associated implications for global climate are unknown. Here we present calculations of the optical properties and direct radiative effects of airborne microplastics (excluding aerosol–cloud interactions). The ERF of airborne microplastics is computed to be 0.044 ± 0.399 milliwatts per square metre in the present-day atmosphere assuming a uniform surface concentration of 1 microplastic particle per cubic metre and a vertical distribution up to 10 kilometres altitude. However, there are large uncertainties in the geographical and vertical distribution of microplastics. Assuming that they are confined to the boundary layer, shortwave effects dominate and the microplastic ERF is approximately −0.746 ± 0.553 milliwatts per square metre. Compared with the total ERF due to aerosol–radiation interactions 27 (−0.71 to −0.14 watts per square metre), the microplastic ERF is small. However, plastic production has increased rapidly over the past 70 years 28 ; without serious attempts to overhaul plastic production and waste-management practices, the abundance and ERF of airborne microplastics will continue to increase. Preliminary modelling of airborne microplastics suggests that they may be exerting a minor cooling influence on the present-day atmosphere, and continued production could have increasing effects on the climate system in future.