What is dust and what does it do?

Dust might drive you nuts, coating everything in a fine layer of gray film that makes your mother shudder in dismay, but it's actually an incredibly diverse collection of matter -- everything from cat dander to cotton lint and pollen particles to persistent bacteria. Strands of hair, spider webs, insect corpses and mold spores are also among the myriad substances that might be lurking in those tumbling dust bunnies.

And while dust might just seem like a nuisance, it's really a very important facet of our atmosphere and climate.

Sitting Around Collecting Dust
Airborne dust particles and water vapor -- also known as aerosols -- waft around the sky along with other substances like ozone and a host of atmospheric gasses. Typically not the same composition as what you'll find in your home, this kind of dust is generally a combination of soot, smoke, pollen, sea salts, soil, sand, ash and all sorts of microorganisms.

The level of particles in the atmosphere varies greatly, both by time and location. Following a volcanic eruption, for example, the number of particles is kicked up considerably. After Krakatau blew its top in 1883, the effects of increased air particles were dramatically enhanced -- sunsets were brilliantly unparalleled for years, and many observers noted eerie, pearly-blue and white clouds feathered across the upper reaches of the atmosphere -- called noctilucent clouds -- for the first time.

These phenomena highlight two of the actions of dust in the atmosphere: light refraction and cloud formation. Water vapor needs particles to condense around and light bounces and bends as it travels through everything suspended in the sky.

Another One Bites the Dust
As with Krakatau, natural events can be a catalyst in changing levels of atmospheric aerosols, but in recent centuries humans have been making quite a contribution too. Growing urban metropolises send huge quantities of dust and other particle emissions up from roadways and factories, along with massive amounts of carbon dioxide. Overgrazing and other poor land management practices also deteriorate soil quality and exacerbate erosion.

Besides aggravating allergy sufferers everywhere, there are other sinister side effects to increasing levels of aerosols in the atmosphere. The planet's climate is incredibly complex, but one of the resulting trends scientists are beginning to see is a vicious cycle of drought, dust storms and desertification emerging in locations around the world.

A recent study done by three research scientists -- Richard Seager of Columbia University's Lamont-Doherty Earth Observatory; Ben Cook from NASA's Goddard Institute for Space Studies and an NOAA global change postdoctoral scholar; and Ron Miller, also from NASA's Goddard Institute for Space Studies -- concluded that during the Dust Bowl of the 1930s, the storms actually compounded this cycle.

"By adding in a dust source over the main region of dust emissions during this period, the model generates a much more intense drought," according to the paper published in the April 2008 Geophysical Research Letters. "These results support the notion that wind erosion and atmospheric dust concentrations were unprecedented in the historical record could have acted as a positive feedback to drought during the Dust Bowl."

More to Explore from HowStuffWorks.com

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Does smog make for beautiful sunsets? 

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How to Allergy-Proof Your Home 

Article posted March 23, 2009.

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