At the end of December, we posted about a disturbing report that Greenland’s glaciers are melting 100 times faster than previously calculated. Now, a new study published this week in the journal Nature reveals that Greenland is warmer than it has been in more than 1,000 years, according to new ice core data.

Newly drilled and analyzed ice cores were used to make a chart of proxy temperatures for Greenland running from the year 1000 to 2011. The plot shows temperatures gently sloping cooler for the first 800 years, then wiggling up and down while sloping warmer until a sharp and sudden spike hotter from the 1990s on. One scientist compared it to a hockey stick, a description used for other long-term temperature data showing climate change.

“We should be very concerned about North Greenland warming because that region has a dozen sleeping giants in the form of wide tidewater glaciers and an ice stream,” said Danish Meteorological Institute ice scientist Jason Box. When awakened, this will ramp up melt from Greenland, he said.

As we noted in our previous post, the melting of the Greenland ice sheet is a major predictor of sea level rise. This frozen stretch of glaciers is the second-largest on Earth and covers about 80% of the Nordic nation. If it melts entirely, as it did at the height of the Eemian interglacial period about 125,000 years ago, global sea levels could rise by 20 feet—or approximately 6.1 meters.

Greenland warming up, experiencing warmest temperatures in 1,000 years