Airborne microplastic radiative effects: a sensitivity study

Microplastics and nanoplastics are recognised as common airborne pollutants, capable of being transported over large distances and altering the radiative properties of the atmosphere, with implications for global climate. Work in recent years has provided new constraints on many aspects of the spatial and temporal distribution of airborne plastics and their physical and optical properties. Using these updated findings, we perform simulations with the HadGEM3-GA7.1 atmospheric model to investigate the sensitivity of the direct radiative effect of airborne microplastics to these factors. Our ERF estimates range from -0.89 to +0.63 mW m^-2 assuming an average surface concentration of 1 MP particle per cubic meter. We show that the sign of the radiative forcing depends on the colour of microplastic particles, and that the abundance of nanoplastics has the strongest influence on the magnitude of their radiative effect, emphasising the importance of experimental work to constrain the micro- and nanoplastic size distribution.