環境：空気中のマイクロプラスチックが気候に及ぼす影響を評価する

Airborne microplastics may have a minor cooling effect on the climate by reflecting solar radiation, suggests a modelling study in Nature. However, as plastic continues to accumulate in the Earth’s environment, a stronger climate effect could be exerted in the future, the paper suggests. The findings present the first calculations of the direct global climate effects of airborne microplastics.

Microplastics are emerging as widespread contaminants in the atmosphere that, owing to their small size and low density, can be transported by winds around the Earth. London, UK and Beijing, China have the highest measured concentrations of airborne microplastics reported to date. Atmospheric aerosols are known to warm or cool the Earth’s climate by absorbing and scattering radiation. However, the radiative effects of airborne microplastics and associated implications for the global climate are currently unknown.

Laura Revell and colleagues used climate modelling to determine the radiative effects of commonly found airborne microplastics. Overall, these microplastics were predominantly found to scatter solar radiation within the lowest part of the atmosphere, suggesting that microplastics may exert a minor cooling influence on the surface climate. However, there are uncertainties in the exact magnitude of this effect owing to a current lack of data, the authors note. They also find that the warming effect of microplastics can, depending on assumptions, counteract much of the cooling.

The abundance of plastic accumulated in landfills and the environment is projected to double over the next three decades. Without serious efforts to address microplastic pollution, mismanaged plastic waste could influence the climate in the future, the authors warn, and may already contribute locally to atmospheric heating and/or cooling.