Black carbon, or soot, is created primarily by either natural sources such as forest fires, or man-made sources, such as industrial pollution caused by burning fossil fuels like coal. Ice core samples taken from Greenland show that between 1880 and the 1950s, the amount of soot that fell on Greenland's glaciers and ice sheets dramatically increased.

During this time, the amount of soot from industrial pollution was seven times greater than the amount of soot from forest fires. New research shows that most of this industrial soot came from North America, and was moved by wind patterns into Greenland.

When soot gathers on snow and ice, it reduces the amount of sunlight the frozen surfaces can reflect, causing them to absorb more of the energy from the sun. This causes ice and snow to melt faster, which exposes rocks, dirt and sea ice that absorbs even more sunlight. New research shows this process lead to increased temperatures in Greenland during this time of increased man-made soot.

Credit: Zina Deretsky, National Science Foundation