A new Nature Climate Change study suggests airborne microplastics -- especially darker and colored particles -- are likely contributing to atmospheric warming by absorbing more heat than they reflect. Researchers estimate the effect could be roughly one-sixth that of black carbon, though outside experts say the uncertainties remain large and more study is needed before drawing firm policy conclusions. "We can say with confidence that overall they are warming agents," said Drew Shindell, a Duke University earth science professor and co-author of the study. "To me, that's the big advance." The Washington Post reports: To undertake their study, a group led by researchers at Fudan University in China examined how different colors and sizes of microplastics interact with light across the spectrum, while combining that information with simulations of how particles get dispersed in the air across the planet.…