Vast stretches of northern Greenland looked like anything but the snowy white North this summer.
That's because huge amounts of soot — from the burning of coal, wood, diesel and dung — have been deposited in the snow and ice.
Danish-based scientist Jason Box says the problem is worse than he ever imagined.
As the snow is darkened by soot, it absorbs more incoming sunlight, causing it to heat up and melt faster.
"Melting in Greenland will affect sea level rise around the planet," Box says.
Watch Duncan McCue's report above or click here to see more.