The fate of the Arctic island has massive implications, regardless of who owns it, writes Andrew Freedman.
While Greenland has experienced the most significant ice loss since the record melt year of 2012, Donald Trump has tried to make light of his interest in buying the island.
The United States under President Donald Trump might not own Greenland (yet), but decisions made by his Administration will help determine the ice-covered island's long-term fate and that of other countries.
US emissions of greenhouse gases, as well as emissions from other countries, have tipped the balance to make Greenland a major contributor to global sea-level rise.
White House sources said last week Trump had asked for information about buying Greenland, the semi-autonomous Danish territory in the Arctic, from Denmark. Trump, who tweeted an image of a Trump Tower in Greenland, said on Monday: "Strategically it's interesting and we'd be interested, but we'll talk to them a little bit. It's not No. 1 on the burner, I can tell you that."
Mette Frederiksen, Denmark's Prime Minister, described the whole affair as "an absurd discussion".
It's no secret that the Greenland ice sheet is in trouble.
This melt season, which is wrapping up, has brought the most significant ice loss, and related sea-level increase, since the record melt year of 2012. Much of the ice melted in a one-week period when the island was in the throes of a heat wave that had moved in from Europe.
According to Ted Scambos, a senior research scientist at the University of Colorado, this year Greenland will add about 1mm to global sea levels through glacial outflow and melt runoff, which translates to about 325 gigatonnes of water entering the North Atlantic Ocean. In addition, the injection of cold freshwater is disrupting ocean circulation, specifically causing a slowdown in the Atlantic Meridional Overturning Circulation, which could alter weather patterns and fisheries.
Greenland ice melt, triggered by increased amounts of carbon dioxide and other greenhouse gases in the atmosphere, has worsened coastal flooding in the United States and elsewhere.
Changes to the island's gravitational pull as a result of shedding so much ice means that some areas are being affected more than others. In Miami, where coastal flooding on sunny days has become a regular hazard, Greenland ice melt has greater effects than in other vulnerable coastal cities, such as Boston.
"Greenland really holds the fate of Miami in its hands in terms of how much sea-level rise is going to come out of there," Scambos said.
Richard Alley, an expert on ice sheets at Penn State University, put the gravitational effects of Greenland ice loss into perspective: "The ice sheet is so massive that its gravity affects the sea level — the ocean is attracted to Greenland's ice enough to raise the sea level around Greenland.
"If the ice melts, the mass is spread out into the world ocean very rapidly, but then the extra water that was held near Greenland also spreads out," Alley said.
Studies have shown that during past periods when Earth was about as warm as it is today, the entire Greenland ice sheet was lost, raising global sea levels by about 7m. With the world on course to experience about 4C of warming above pre-industrial levels by 2100, it's possible we'll pass a critical threshold beyond which there's no preventing a complete or near-complete disappearance of the ice sheet.
"The critical threshold temperature is poorly known, but is not too many degrees above modern, [and] almost surely can be reached by human-caused warming if we continue to emit carbon dioxide rapidly from fossil-fuel burning and other processes," Alley said.
Already, Greenland's rate of ice loss has increased sixfold since the 1980s, going from 37 gigatonnes per year during the 1990s to 259 gigatonnes per year during the period from 2010.
The rate and extent of surface melting across the Greenland ice sheet can quickly change with even a small amount of warming. "Raising the temperature by a degree or two more in summer means that a huge area of the ice sheet will begin to melt," Scambos said.
A recent study in the journal Proceedings of the National Academy of Sciences found that in a high-emissions scenario, Greenland could contribute up to 60cm of global sea-level rise by 2100.
Other studies have shown that if significant emissions cuts are made in the next decade or two, the total amount of sea-level rise from Greenland, as well as Antarctica and other sources, could still be limited.
But time is running out, regardless of who "owns" Greenland.