Climate Change Uncertainty Cleared Up by Broken Glass

A new understanding of climate change comes from an unlikely source: broken glass. A major uncertainty in climate modeling is dust’s exact role in past and future changes. New research provides some clarity and also has strong implications for regional weather forecasting.

The research published in this week’s Proceedings of the National Academy of Sciences focuses on the ratio of different sizes of dust particles, particularly clay and silt. Of the two, clay is smaller than silt.

How small are they exactly? Clay particles are less than two microns across while silt is anything larger, up to 20 microns. A human hair is 50 microns wide so clearly we’re talking about a very tiny scale here.

The way these particles reach the atmosphere is pretty amazing. Dust particles smaller than 20 microns tend to be so cohesive that wind doesn’t move them. Larger particles between 70-500 microns (roughly the size of sand) are more easily lifted by the wind, though, and when they come crashing to the ground, they break apart smaller particles and send them flying into the air.

The ratio of the different sized particles has been poorly understood, though. Knowing that ratio is important. The size of the particles, or aerosols, affects whether they have a net warming or cooling effect. Smaller particles have a stronger cooling effect. More them means dust clouds will help cool the Earth more.

Drinking Glasses: More Like Dust Than You’d Expect

So where does the broken glass fit in? When you drop a glass, it shatters into pieces of a variety of shapes and sizes. It’s not as random as it seems, though. There are equations that explain the fracture patterns and ratios. Jasper Kok, the researcher at the National Center for Atmospheric Research who did the study, thought to apply these equations to the interaction of sand and dust.

The results were striking. It turns out shards of glass and pieces of dust follow the same distribution pattern. That ratio also happens to be dramatically different from current estimates. The results show that climate models have been overestimating the portion of clay to silt aerosols by a factor of two to eight. They also show that models underestimate the volume of large particles in dust clouds.

The Benefits for Climate and Weather Predictions

The findings advance our understanding of climate change in a number of ways. Because there are fewer small aerosols in dust clouds, it’s possible that climate models have been overestimating their cooling properties. Larger particles also tend to stay in the atmosphere within 1000 miles of the region they came from. Using the new findings could improve the accuracy of climate projections for desert regions.

Another modeling improvement that could come out of this research is the transfer of nutrients to the ocean. Dust particles help fertilize plant life in the ocean by depositing iron. Because there are more large particles than previously thought, it means there might be substantially more iron reaching the ocean. This would translate more plant life which sucks up carbon dioxide from the atmosphere.

Finally, there’s the benefit to local weather forecasting in dust-prone areas. Aerosols play a key role in cloud formation and precipitation. Their exact effect depends in large part on their size. Having a better idea of the composition of dust clouds could improve forecasts to the benefit people in places like the American Southwest and northern Africa, particularly those in precipitation-dependent lines of work like farming.

The research goes to show that applying a simple idea to a complex problem can provide a major breakthrough. Who knows? Maybe the solution to addressing climate change is sitting in your living room right now.

Photo credits: Brian Kahn and University Corporation for Atmospheric Research