It is an everyday affair; tackling it is at the heart of morning rituals across cultures and continents. In its vile form, dust can take a big toll on economic activity, such as when ash from Eyjafjallaj?kull brought air traffic across Europe to a halt. But it can also deliver intercontinental miracles. For example, while the soil of the Amazon rainforest is deficient in minerals, it is able to thrive thanks to the bounty flying in from the distant Sahara. Ultimately, understanding how dust works is imperative because of how it impacts climate and ocean ecology, understanding which is in turn key to better climate modelling, more accurate predictions. Two recently published papers show important advances in causes and effects of dust.
Anthropomorphic Aerosols
Research led by a Cornell University atmospheric scientist Natalie Mahowald, published in Atmospheric Chemistry and Physics,shows there is twice as much desert dust in the atmosphere than there used to be around a century ago. The researchers looked at an array of data pertaining to the 1900-2000 period, like data about remnants of South American soil found in the ice cores of Antarctica. Agriculture, pasture use and other human activities have contributed to this trend. The complication comes from how desert particles affect the atmosphere, both raising and lowering temperatures depending on context. Studies of sediment deposited at the bottom of a Tibetan lake, for example, reveal fine particulate flow from distant deserts. Broadly, we know that when such dust darkens ice, radiation absorption accelerates as does glacial melting. Dust also disrupts cloud formation and thus aids desertification. On the other hand, iron-rich dust can encourage plankton growth in the oceans, allowing them to pull in more carbon from the air. Dust can also reflect sunlight back into space. There is a lot of ambivalence at play here, which seems to be par for the course as far as climate change is concerned. No wonder Mahowald has said that her team puts big uncertainty bars on everything and underlines that more data is needed. Still, the Mahowald study suggests that, even as atmospheric dust levels doubled during the last century, they helped offset up to a third of the impact of global warming.
Like Broken Glass
As the need to know why some dust particles cool the planet while others trap heat grows, a study by Jasper Kok of the National Centre for Atmospheric Research in Colorado, published in Proceedings of the National Academy of Sciences, makes a helpful contribution to figuring out the behaviour of dust. He begins with the finding that if you drop a glass on the floor, it doesn?t crack randomly but in a mathematically predictable way. What is more, dust in dust storms acts as per the same mathematical principles. Like Mahowald, Kok underlines that more extensive studies will be needed to confirm that when dust particles strike the soil, they create cracks in exactly the same way as broken glass. But if this is indeed the case, then it will represent a big breakthrough for climate modelling, not least because the same model would actually work for different soils!
Albeit to a very different end, the Magisterial Emissary in The Golden Compass declares, ?If we can protect our children from the corrupting influence of Dust… then we will nurture a generation at peace with itself.? Whatever the scientists are up to, common folk are busy (vainly) wiping out dust. Well, it?s a comfort that some smart people are on our side: Malay Mazumdar, electrical and computer engineering professor at Boston University, has found that a dust layer of merely 4g per square metre decreases solar power output by more than 40%. So keep wiping away.