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^{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25}. 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) metric²⁶. 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 interactions²⁷ (−0.71 to −0.14 watts per square metre), the microplastic ERF is small. However, plastic production has increased rapidly over the past 70 years²⁸; without serious attempts to overhaul plastic production and waste-management practices, the abundance and ERF of airborne microplastics will continue to increase.

微塑料现在被认为是大气中广泛存在的污染物，由于它们体积小、密度低，它们可以随风在地球周围^{传播 1,2,3,4,5,6,7,8,9,10 ,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25}。大气气溶胶，例如矿物粉尘和其他类型的空气悬浮颗粒物，通过吸收和散射辐射（直接辐射效应）影响地球气候，它们的影响通常用有效辐射强迫 (ERF) 指标进行量化²⁶. 然而，空气中微塑料的辐射效应以及对全球气候的相关影响尚不清楚。在这里，我们介绍了空气中微塑料的光学特性和直接辐射效应的计算（不包括气溶胶-云相互作用）。假设每立方米 1 个微塑料颗粒的均匀表面浓度和高达 10 公里的高度垂直分布，则空气中微塑料的 ERF 在当今大气中计算为每平方米 0.044 ± 0.399 毫瓦。然而，微塑料的地理和垂直分布存在很大的不确定性。假设它们被限制在边界层内，短波效应占主导地位，微塑料 ERF 约为每平方米 −0.746 ± 0.553 毫瓦。²⁷（每平方米 -0.71 至 -0.14 瓦），微塑料 ERF 很小。然而，塑料产量在过去 70 年里增长迅速²⁸；如果不认真尝试彻底改革塑料生产和废物管理做法，空气中微塑料的丰度和 ERF 将继续增加。