When it comes to global warming, some of the most dramatic images come from Greenland, where melting glaciers are breaking apart and sending rivers of water into the ocean.
Greenland's ice sheets are receding at least twice as fast at at any time in the past 9,500 years, according to a new study from Columbia University's Earth Institute.
The changes taking place could have big impacts for sea level rise and coastal cities, including those along the California coast.
"What happens in the ice sheets of Greenland and Antarctica affect all of us all around the world," said Laurence Smith, chair of Geography at UCLA and author of 'The World in 2050.' "These ice sheets are losing mass to the ocean, which raises sea level."
Smith led a research team to Greenland this summer as part of an ongoing study to compare on-the-ground conditions to computer modelling and satellite images of the area.
"To my knowledge, we collected the first-ever direct measurements of melt water runoff flowing off the surface of the ice sheet," said Smith.
The bottom line?
"If Greenland were to somehow disappear right now, it would not reform," said Smith. And that is worth paying attention to, he said.