A groundbreaking study reveals that microplastic and nanoplastic particles in the air may significantly contribute to global warming, rivalling the impact of black carbon emissions.
Key Points
- Airborne microplastics and nanoplastics may contribute significantly to global warming.
- Coloured plastic particles absorb more sunlight, increasing their warming effect.
- The warming effect of microplastics can be higher in ocean regions with high plastic concentrations.
- Further research is needed to fully understand the impact of microplastics on climate change.
Airborne micro- and nanoplastic particles may contribute to global warming at over 16 per cent of the impact of black carbon, or 'soot', with higher values observed above ocean garbage patches, according to a study.
The findings, published in the journal Nature Climate Change, suggest that the plastic particles might previously have been unrecognised contributors to climate warming, but their role should be considered in future climate assessments, researchers said.
The Impact of Coloured Microplastics
The team, including researchers from China's Fudan University and the US, examined the behaviour of individual micro- and nanoplastic particles and found that black and coloured particles strongly absorb sunlight compared to white particles.
The authors "show that coloured MNPs (microplastic and nanoplastic particles) exhibit strong light absorption, with a mean refractive index of 1.49-0.22i at 550 nm (nanometres) and absorption coefficients 74.8 times higher than those of pristine particles."
Microplastics and nanoplastics are formed when larger plastic waste fragments. They are sized between one nanometre (one billionth of a metre) to up to 500 micrometres (one millionth of a metre) in diameter.
Studies have detected microplastics and nanoplastics in varied environments, including the human brain.
Re-evaluating Atmospheric Warming
Previous studies have suggested that the contribution of airborne plastics to atmospheric warming is minimal, but such analyses often assumed that they were uncoloured, despite real-world plastics commonly containing pigments, the researchers said.
The team said that the effective radiative forcing -- the difference between solar radiation absorbed and released by a planet's atmosphere -- for microplastic and nanoplastic particles is equivalent to 16.2 per cent of that from black carbon emissions, a well-known air pollutant that contributes to warming.
"Resulting simulations yield mean DRF (direct radioactive forcing) of 0.039±0.019 Wm-2 (Watts per square metre) for MNPs, equivalent to 16.2 per cent of black carbon forcing," the authors wrote.
Regional Climate Impact
Although the warming effect is small at the global level, it can exceed that of black carbon by up to a factor of 4.7, especially over ocean regions with high concentrations of plastic, such as the North Pacific Garbage Patch, they said.
The study's findings indicate that airborne plastic particles, particularly coloured nanoplastics, contribute to atmospheric warming and may influence regional climate patterns, the researchers said.
They noted that the laboratory experiments are a simplified version of atmospheric processes and that the global distribution of micro- and nanoplastic particles needs to be better estimated by observations.
The team said further research is required to fully determine how micro and nanoplastics contribute to Earth's warming and to improve their representation in climate models.
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