A rarely-considered aspect of global warming

If all we are is dust in the wind, it turns out we could be pretty lasting and important. Dust plays a major role in climate - possibly more of one than we give it credit for.

Fit of rage, moment of clumsiness, evening in a Greek restaurant; we've all smashed something in our time. We're used to seeing the uneven pieces with their uneven distribution coat our floor. We're also used to finding a few slivers of glass or ceramic left over, even when we're sure that we've cleaned up every last piece. When it comes to shattering, most people think of big objects, like stones or plates. But small objects like pebbles, sand and tiny pieces of clay, shatter and scatter in similar ways. The main difference is, their shards are light enough to waft through the air.


These tiny shards range from 2 to 50 microns wide. The upper limit of 50 is about the diameter of a human hair. The lower one is far below the limit visible to the eye. They're all visible to the sun, though, and they do their part in making the planet a hotter or cooler place. Smaller is better. Tiny pieces of clay, 2 microns wide, are light enough to drift through the air for a long time. While there, they dutifully reflect sunlight back up through the atmosphere, and slightly cool the planet. Heavier pieces of dust, however, soak up the heat and keep it in the atmosphere.

These heavy pieces only stay airborne for a few days, but some scientists think they have been greatly under-represented in current computer models. The ratio of large to small particles in the sky may be up to eight times greater than currently thought. What's more, the bigger pieces of silt congregate near regions that are already hot and dry, like deserts and plains. These means that these places will be even more greatly affected by climate change than currently predicted. Even wet and snowy areas aren't safe. When these pieces of dust settle in snow, they absorb heat from sunlight more readily than the snow itself, meaning the snow has little heaters embedded in it. It will melt more quickly than pure snow.

New mathematical formulas are being devised to reassess the way things shatter, and the way that the detritus left behind affects global temperature. With luck, we will be able to get much more accurate weather information, climate change predictions, and materials research. It's time to literally see the world in a grain of sand.

Via UCAR and PNAS.


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