Polluted clouds at air pollution hot spots help to better understand anthropogenic impacts on Earth’s climate
Date
2022-07-13
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Abstract
Inimtekkelised õhusaasteosakesed jahutavad Maa kliimat ja kompenseerivad osa kasvuhoonegaaside soojendavast kliimamõjust. Õhusaasteosakeste jahutava kliimamõju täpne ulatus on ebaselge, kusjuures määramatus võrreldes kasvuhoonegaaside soojendava efektiga palju suurem. Kõige ebaselgem on seejuures õhusaasteosakeste mõju pilvedele. Pilved ja sademed tekivad Maa atmosfääris tänu sellele, et õhku on pihustunud tahkeid või vedelaid väikeseid osakesi, mille ümber veeaur kondenseerub. Inimtekkelise õhusaaste tõttu on atmosfääris selliseid väikeseid osakesi rohkem, ning see põhjustab muutusi pilvede omadustes. Antud töös võrdleme isoleeritud saasteallikate heitmetest tugevalt saastunud pilvede omadusi kõrvalasuvate saastumata pilvedega. Täpsustame inimtekkeliste õhusaasteosakeste kliimamõju ulatust, analüüsides kui sagedasti ja millistes ilmaoludes on inimtekkelistel õhusaasteosakestel tugev mõju pilvede omadustele. Näitame, et vastupidi kliimamudelites kasutatud eeldusele, saasteosakeste mõjul pilvede keskmine paksus ei kasva. See tulemus viitab, et õhusaasteosakeste jahutav mõju ei ole nii tugev nagu seni on arvatud. Doktoritöö tulemused aitavad luua usaldusväärsemaid tuleviku kliima projektsioone.
It is unknown to what extent the cooling effect of the anthropogenic air pollution particles called aerosols offsets the warming effect of greenhouse gases. It is especially uncertain how strong is the cooling effect exerted by aerosol-induced changes in cloud properties. Clouds and precipitation can form in the Earth’s atmosphere thanks to the fine solid and liquid particles suspended in the atmosphere. Due to anthropogenic air pollution, there are more aerosol particles in the atmosphere leading to changes in cloud properties. Here, we compare the properties of clouds polluted by emissions from strong isolated aerosol sources to the nearby unpolluted clouds. We show that strong anthropogenic cloud perturbations occur intermittently and only in the case of favourable meteorological conditions. We challenge the assumption of unidirectional increases in cloud thickness in contemporary climate models and show that the cloud thickness does not increase in response to aerosols on average. This indicates that the cooling effect of anthropogenic aerosols on Earth’s climate might not be as strong as previously assumed. Our results will ultimately lead to more reliable climate projections.
It is unknown to what extent the cooling effect of the anthropogenic air pollution particles called aerosols offsets the warming effect of greenhouse gases. It is especially uncertain how strong is the cooling effect exerted by aerosol-induced changes in cloud properties. Clouds and precipitation can form in the Earth’s atmosphere thanks to the fine solid and liquid particles suspended in the atmosphere. Due to anthropogenic air pollution, there are more aerosol particles in the atmosphere leading to changes in cloud properties. Here, we compare the properties of clouds polluted by emissions from strong isolated aerosol sources to the nearby unpolluted clouds. We show that strong anthropogenic cloud perturbations occur intermittently and only in the case of favourable meteorological conditions. We challenge the assumption of unidirectional increases in cloud thickness in contemporary climate models and show that the cloud thickness does not increase in response to aerosols on average. This indicates that the cooling effect of anthropogenic aerosols on Earth’s climate might not be as strong as previously assumed. Our results will ultimately lead to more reliable climate projections.
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Keywords
industry, discharge, air pollutants, air quality, clouds, aerosols, human impact, climate change