By Laura Paddison, CNN
(CNN) — Out in the Pacific Ocean, between Hawaii and California, is the Great Pacific Garbage Patch, a swirl of plastic trash more than twice the size of Texas. As pieces of plastic tumble against each other, they break down into particles tiny enough to be borne aloft on the wind. Once in the air, they have a climate impact that could affect us all, according to new research.
The Great Pacific Garbage Patch is a significant source of airborne microplastics and nanoplastics, but there are many other places where tiny plastic particles can be whipped up into the skies, including from landfills, roadside litter and car tires.
A team of scientists from China and the US have studied the makeup and behavior of these plastics, and found they are contributing to global heating, according to the study published Monday in the journal Nature.
Most microplastics research has focused on their health and environmental dangers, but this report “reveals a long overlooked link between plastic pollution and climate change,” said Hongbo Fu, a study author and an atmospheric scientist at Fudan University in Shanghai.
The scientists zoomed in on microplastics, usually the size of a pencil eraser or smaller, and nanoplastics, which are the tiniest particles, many times smaller than the width of a human hair. They analyzed color, size and chemistry to understand more about how they interact with sunlight.
They wanted to know whether particles scattered sunlight back into space — meaning they would have a cooling influence on the planet — or whether they absorbed sunlight, which would have a warming impact.
Previous research has suggested microplastics’ contribution to global warming was negligible, but analyses have often assumed particles were clear, the report scientists said. What they found was a rainbow of colors.
Colored plastics, especially red, yellow, blue and black, absorbed around 75 times more light than pristine, non-pigmented plastics, the study found. They “act like black T-shirt; they soak up heat,” Fu said.
Size is also a factor, although to a lesser extent. The smaller the particle, the more sunlight it was able to absorb, the report found. “Nanoplastics are tiny but powerful. They stay in the air longer and, for the same mass, they absorb much more sunlight than microplastics,” Fu said.
The scientists also found the plastics’ warming impact could change over time. They artificially aged them in the lab using ultraviolet lamps and found that white particles tended to yellow, meaning they absorbed more sunlight. Red particles, on the other hand, sometimes bleached, meaning they scattered more light.
Most particles are darker, either because they start that way or darken as they float around the atmosphere and age, said Drew Shindell, a study author and a professor of Earth science at Duke University. The big advance of the paper, is that “we can pin down that the net effect is that almost all of these particles are warming more than cooling,” he said.
The warming effect may be small at a global level but it’s not insignificant, the scientists said. Microplastics and nanoplastics produce roughly 16% the warming impact of black carbon, or soot, a powerful airborne pollutant.
In ocean areas where plastic gets caught in spinning currents, such as the Great Pacific Garbage Patch, the warming impact is particularly pronounced and may exceed black carbon, the study found. It’s “bits of plastic hitting other bits of plastic that causes the extra-large flux of material out into the atmosphere,” Shindell said.
Experts told CNN the study results are interesting and build on previous findings, but do have significant li