Not sure about airborne microplastic. But research suggest that microplastic in Marine environment may contribute to increased levels of CO2. The Marine phytoplankton which consume CO2 during photosynthesis are affected by presence of microplastics and their productivity may decrease due to the presence of microplastics in their ecosystem, thereby increasing the CO2 levels, which otherwise would have been fixed. This link may be of further help
Knowledge of the existence of microplastics in the atmosphere is fairly recent. As a result, it is not yet known whether these microplastics contribute to climate change or not. Research is needed on this subject.
Mannan.... Plastic fine particles are even more effective than dust particle suspended in air. Their chemical composition suggests that they may affect even the UV radiation passing through them as a result of the possible light absorption of their components. However, this may be a good topic to study... Good luck
Useful link, please see the following paper it include excellent information about the airborne microplastic analysis , occurrence, movement and risks.
Article Airborne microplastics: a review study on method for analysi...
Plastic particles in air can absolutely affects the climate their effects on UV radiation, on the light absorption, and CO2 but more question is 'to what extent' and this can open new line of research based on their chemical compositions