Dust particles in the atmosphere can influence climate

Jasper Kok said there are several times more dust particles in the atmosphere than previously thought. This can be a problem because dust particles can contribute to heating and cooling of the planet on an atmospheric level depending on their size and other characteristics. Some dust particles can reflect solar energy and cool the planet, while others trap the energy as heat.

The study focuses on a type of airborne particle known as mineral dust, which is usually emitted when grains of sand are blown, sending dirt fragments into the air. These fragments can be as tiny as 2 microns in diameter or as large as about 50 microns in diameter – about the thickness of a strand of human hair.

Depending on their size, the particles stay in the atmosphere for different durations and can have a cooling or a warming influence in the air. The smallest particles, or clay, stay in the atmosphere for about a week and reflect heat back for a cooling effect, while the larger particles, or silt, remain only for a few days, creating a heating effect.

The ratio of silt particles to clay particles is two to eight times greater than represented in climate models, and the study suggests that current models most likely commit error when it comes to the number of silt particles.

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Higher dust concentration occurs because shattered dust appears to produce a higher amount of large dust fragments, Mr. Kok said. He compared the shattered dust to fragment patterns of broken glass and other brittle objects.

Brittle objects fracture in predictable patterns called scale invariance or self-similarity that follows a certain predictable range of sizes. Physicists have devised mathematical formulas that allow them to predict scale invariance and Mr. Kok used the same formulas to estimate the range of dust particle sizes.

“As small as they are, conglomerates of dust particles in soils behave the same way on impact as a glass dropped on a kitchen floor,” he explained. “Knowing this pattern can help us put together a clearer picture of what our future climate will look like.”

By applying this new knowledge to their climate models, climate scientists would be able to better determine the influence of dust on the climate.

The National Science Foundation, which sponsors the National Center for Atmospheric Research, supported the study. Mr. Kok’s findings were published in the Proceedings of the National Academy of Sciences.



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