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タイトル：マイクロプラスティックが地球温暖化にどのように貢献しているか
記事によると、中国の復旦大学を中心に研究された新しいNature Climate Changeの論文は、空気中のマイクロプラスチックが反射するよりも吸収する熱が多い可能性があることを示しています。特に濃色や彩色された粒子は、ブラックカーボン（化石燃料を燃やす際に生成される煙の一部）と比較して大さな暖房源ではないとしても無視できるものでもないとされています。
研究者たちは、マイクロプラスチックが大気中で地球温暖化にどれほど寄与しているかを推定し、その影響はブラックカーボンの約六分の一であると推測しました。この推定値によると、1年間の世界中のマイクロプラスティックスの排出量は200基の石炭火力発電所が同一年間稼働した場合に匹敵する据え置き効果があります。
研究者たちはまた、粒子が老いていくと吸収度がどのように変わるかも調査しました。黒や彩色された粒子は、白色の粒子よりも75倍以上の吸収度を示すことが明らかになりました。この推定値は未だに不確実性が高く、より多くの研究が必要であることも強調されています。
この論文は現在の気候モデルで考慮されていない大気中の微細な粒子による追加的な暖房効果についても更なる研究が必要であると述べています。
A new Nature Climate Change study suggests airborne microplastics -- especially darker and colored particles -- are likely contributing to atmospheric warming by absorbing more heat than they reflect. Researchers estimate the effect could be roughly one-sixth that of black carbon, though outside experts say the uncertainties remain large and more study is needed before drawing firm policy conclusions. "We can say with confidence that overall they are warming agents," said Drew Shindell, a Duke University earth science professor and co-author of the study. "To me, that's the big advance." The Washington Post reports: To undertake their study, a group led by researchers at Fudan University in China examined how different colors and sizes of microplastics interact with light across the spectrum, while combining that information with simulations of how particles get dispersed in the air across the planet. "Black, yellow, blue and red [particles] absorb sunlight much more strongly than the white particles," Yu Liu, a Fudan professor and study co-author, said in a call with reporters. In fact, the study details how black and colored particles showed "absorption levels nearly 75 times higher than pristine, non-pigmented plastics." The scientists also found that different sizes of particles absorb light at different intensities -- and that how they absorb light can change as they age.
The authors estimate that microplastics suspended in the atmosphere could be contributing to global warming at about one-sixth the amount of black carbon, also known as soot, a pollutant generated largely from burning fossil fuels. If the latest estimates are right, Shindell said, microplastics might not be an enormous source of atmospheric warming, compared with massive contributors such as cars and trucks, belching industrial plants or even burping cows. "But not a trivial one, either," he said.
By his calculation, the effect of one year's microplastic emissions globally is approximately equivalent to 200 coal-fired power plants running for that year. But that rough estimate does not factor the longer-term repercussions of microplastics decaying and persisting in the environment for decades to come. Whatever the exact impact, the topic deserves further study, the authors say, because current climate modeling does not account for any additional warming that these tiny particles might be causing.
Read more of this story at Slashdot.
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