A sharp spike in Greenland temperatures since 1995 showed the giant northern island 2.7 degrees hotter than its 20th-century average, the warmest in more than 1,000 years, according to new ice core data.
Until now Greenland ice cores — a glimpse into long-running temperatures before thermometers — hadn’t shown much of a clear signal of global warming on the remotest north central part of the island, at least compared to the rest of the world. But the ice cores also hadn’t been updated since 1995. Newly analyzed cores, drilled in 2011, show a dramatic rise in temperature in the previous 15 years, according to a study in Wednesday’s journal Nature.
Felipe Dana, AP file photo
A boat navigates at night next to large icebergs on Aug. 15, 2019, near the town of Kulusuk in eastern Greenland.
“We keep on (seeing) rising temperatures between 1990s and 2011,” said study lead author Maria Hoerhold, a glaciologist at the Alfred Wegener Institute in Germany. “We have now a clear signature of global warming.”
It takes years to analyze ice core data. Hoerhold has new cores from 2019 but hasn’t finished studying them yet. She expects the temperature rise to continue as Greenland’s ice sheet and glaciers have been melting faster recently.
“This is an important finding and corroborates the suspicion that the ‘missing warming’ in the ice cores is due to the fact that the cores end before the strong warming sets in,” said climate scientist Martin Stendel of the Danish Meteorological Institute, who wasn’t part of the research.
The ice cores are used to make a chart of proxy temperatures for Greenland running from the year 1000 to 2011. It 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.
The jump in temperature after 1995 is so much larger than pre-industrial times before the mid-19th century that there is “almost zero” chance that it is anything but human-caused climate change, Hoerhold said.
The warming spike also mirrors a sudden rise in the amount of water running off from Greenland’s melting ice, the study finds.
What had been happening in Greenland is that natural weather variability, undulations because of an occasional weather system called Greenland blocking, in the past had masked human-caused climate change, Hoerhold said.
But as of about 25 years ago, the warming became too big to be hidden, she said.
Past data also showed Greenland not warming as fast as the rest of the Arctic, which is now warming four times faster than the global average. But the island appears to be catching up.
Ice core data for years showed Greenland acted a bit differently from the Arctic. That’s likely because of Greenland blocking, Hoerhold said. Other scientists said as a giant land mass Greenland was less affected by melting sea ice and other water factors compared to the rest of the Arctic, which is much more water-adjacent.
Hoerhold’s team drilled five new cores near old cores so as to match established ice core records. They use the difference between two different types of oxygen isotopes found in the ice to calculate temperature, using an already established formula that is checked against observed data.
Hoerhold and outside scientists said the new warming data is bad news because Greenland’s ice sheet is melting. In fact, the study ends with data from 2011. The next year had a record melt across Greenland, and the island’s ice loss has been high since then, she said.
“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, it will ramp up melt from Greenland, he said.
And that means “rising seas that threaten homes, businesses, economies and communities,” said U.S. National Snow and Ice Data Center Deputy Lead Scientist Twila Moon.
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Sandy Virgo
The world's largest island sits between the Atlantic and Arctic oceans. A 1.7-million-square-kilometer (660,000-square-mile) ice sheet covers 80 percent of the Arctic territory.
In this image taken on June 13, 2019 small pieces of ice float in the water off the shore in Nuuk, Greenland. (AP Photo/Sandy Virgo)
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Keith Virgo
Greenland's 56,000 residents are mainly Inuits, the indigenous people. They are concentrated on the west coast in small towns and hamlets or remote coastal settlements where life revolves around fishing and the hunting of seals and whales.
In this image taken on June 20, 2019 Sadelo mountain, also known as Sermitsiaq, can be seen surrounded by Nuup Kangerlua fjord, in Nuuk, Greenland. (AP Photo/Keith Virgo)
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Felipe Dana
Greenland is part of the Danish realm along with the Faeroe Islands and has its own government and parliament, the 31-seat Inatsisartut. In 1979, Greenland gained home rule from Denmark. Its premier is Kim Kielsen of the left-leaning Siumut party. A police officer-turned politician, Kielsen has been in office since 2014.
In this photo from Thursday, Aug. 15, 2019, dogs sit outside a home in Kulusuk, Greenland. (AP Photo/Felipe Dana)
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Felipe Dana
Greenland's economy depends of fisheries and related industries, as well as annual subsidies of 4.5 billion kroner ($670 million) from Denmark, which handles its foreign affairs and defense matters.
In this photo taken Thursday, Aug. 15, 2019, an iceberg floats near a cemetery in Kulusuk, Greenland. (AP Photo/Felipe Dana)
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Felipe Dana
The effects of climate change have been particularly dramatic for Greenland, which has seen one of its biggest ice melts on record this summer, contributing to a global rise in sea levels.
In this photo taken on Wednesday, Aug. 14, 2019, Icebergs are covered by clouds near Kulusuk, Greenland. (AP Photo/Felipe Dana)
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Linda Kastrup
Due to global warming, it is believed that oil and other mineral wealth could become more accessible in the Arctic — and Greenland. Nations including Russia, China, the U.S., and Canada are racing to stake as strong a claim as they can to Arctic lands, hoping they will yield future riches.
This July 11, 2015 file photo shows a general view of the town of Upernavik in western Greenland. (Linda Kastrup/Ritzau Scanpix via AP)
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Felipe Dana
If these resources are successfully tapped, they could dramatically change the island's fortunes. However, no oil has yet been found in Greenlandic waters and the thickness of the ice means exploration is only possible in coastal regions.
In this photo from late Friday, Aug. 15, 2019, a boat navigates at night next to a large iceberg in eastern Greenland. (AP Photo/Felipe Dana)
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Felipe Dana
In 2013, the sparsely populated island removed a 25-year-old ban on uranium mining since the element is often found mixed with other rare earth metals used for smartphones and weapons systems. A southern Greenland mine could be the largest rare-earth metals deposit outside China, which currently accounts for more than 90 percent of global production.
Photo: A local man smokes a cigarette as he rides on a boat past icebergs in eastern Greenland, late Friday, Aug. 15, 2019. (AP Photo/Felipe Dana)
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Felipe Dana
Conditions are far from ideal and searches for minerals have stalled. Chiefly because of poor infrastructure, lack of sufficient manpower and long winters with frozen ports, 24-hour darkness and temperatures often below minus 30 Celsius (minus 20 Fahrenheit) in the northern parts.
Photo: A boat navigates at night between icebergs in eastern Greenland, late Friday, Aug. 15, 2019. (AP Photo/Felipe Dana)
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Felipe Dana
The United States also tried to buy the world's largest island in 1946. Washington offered Denmark $100 million for Greenland after flirting with the idea of swapping land in Alaska for strategic parts of the Arctic island. Denmark turned the offer down then as well.
Photo: A boat navigates at night between icebergs in eastern Greenland, late Friday, Aug. 15, 2019. (AP Photo/Felipe Dana)
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Felipe Dana
Under a 1951 deal, Denmark allowed the U.S. to build rent-free bases and radar stations on Greenland. The U.S. Air Force currently maintains only one base in northern Greenland, Thule Air Force Base, 1,200 kilometers (745 miles) south of the North Pole. Former military airfields in Narsarsuaq, Kulusuk and Kangerlussuaq have become civilian airports.
Photo: An aerial view of large Icebergs floating as the sun rises near Kulusuk, Greenland, early Friday, Aug. 16, 2019. (AP Photo/Felipe Dana)
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Felipe Dana
The Thule base, constructed in 1952, was originally designed as a refueling base for long-range bombing missions. It has been a ballistic missile early warning and space surveillance site since 1961.
In this photo taken late Friday, Aug. 16, 2019, homes are illuminated after the sunset in Tasiilaq, Greenland. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, large Icebergs float away as the sun rises near Kulusuk, Greenland. Scientists are hard at work, trying to understand the alarmingly rapid melting of the ice. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, a boat navigates at night next to a large iceberg in eastern Greenland. Summer 2019 is hitting Greenland hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons (400 billion metric tons) of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, a helicopter carrying New York University air and ocean scientist David Holland and his team sits on the ice as they install a radar and GPS at the Helheim glacier, in Greenland. Scientists are hard at work there, trying to understand the alarmingly rapid melting of the ice. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, a boat navigates at night next to large icebergs near the town of Kulusuk, in eastern Greenland. Greenland's ice has been melting for more than 20 years, but in 2019, it's as if Earth's refrigerator door has been left open, and it means a potentially large rise in the world's sea levels. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, a woman stands next to an antenna at an NYU base camp at the Helheim glacier in Greenland. Summer 2019 is hitting the island hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, a boat navigates next to a large iceberg in eastern Greenland. Greenland's ice has been melting for more than 20 years, but in 2019, it's as if Earth's refrigerator door has been left open, and it means a potentially large rise in the world's sea levels. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, early morning fog shrouds homes in Kulusuk, Greenland. In tiny Kulusuk, resident Mugu Utuaq says the winter that used to last as long as 10 months when he was a boy, can now be as short as five months. Scientists are hard at work in Greenland, trying to understand the alarmingly rapid melting of the ice. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, Brian Rougeux, NYU Field Safety Officer, installs a GPS antenna at the Helheim glacier, in Greenland. An NYU team is tracking what's happening in Greenland from both above and below. The head of the New York University team, air and ocean scientist David Holland, calls Greenland "the end of the planet" referring to geography more than the future. Yet in many ways Greenland is where the planet's warmer and watery future is being written. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, NYU student researchers sit on top of a rock overlooking the Helheim glacier in Greenland. Summer 2019 is hitting the island hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. Helheim glacier has shrunk about 6 miles (10 kilometers) since scientists visited in 2005. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, New York University air and ocean scientist David Holland, left, and field safety officer Brian Rougeux, right, are helped by pilot Martin Norregaard as they carry antennas out of a helicopter to be installed at the Helheim glacier, in Greenland. Holland and his NYU team are tracking what's happening in Greenland from both above and below. He calls it "the end of the planet" referring to geography more than the future. Yet in many ways Greenland is where the planet's warmer and watery future is being written. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, a boat navigates at night next to large icebergs in eastern Greenland. Greenland's ice has been melting for more than 20 years. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, a helicopter flies over hundreds of icebergs floating near the Helheim glacier, in Greenland. Summer 2019 is hitting the island hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. Helheim glacier has shrunk about 6 miles (10 kilometers) since scientists visited in 2005. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, Brian Rougeux, NYU Field Safety Officer, walks after installing a flag to help identify a GPS position at the Helheim glacier, in Greenland. Summer 2019 is hitting the island hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. Helheim glacier has shrunk about 6 miles (10 kilometers) since scientists visited in 2005. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, Mugu Utuaq, left, reloads his rifle as he rides with other boats hunting whales near Kulusuk, Greenland. Summer in 2019 is hitting the island hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, a boat navigates at night next to a large iceberg in eastern Greenland. Summer 2019 is hitting Greenland hard with record-shattering heat and extreme melt. By the end of the summer, about 440 billion tons (400 billion metric tons) of ice, maybe more, will have melted or calved off Greenland's giant ice sheet, scientists estimate. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, boys carry plastic bags full of fish in Kulusuk, Greenland. According to local resident Mugu Utuaq, the winter that used to last as long as 10 months when he was a boy can now be as short as five months. Scientists are hard at work in Greenland, trying to understand the alarmingly rapid melting of the ice. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, crosses stand in a cemetery as an iceberg floats in the distance during a foggy morning in Kulusuk, Greenland. Kulusuk's resident Mugu Utuaq says the winter that used to last for as long as 10 months when he was a boy can now be as short as five months. Scientists are hard at work in Greenland, trying to understand the alarmingly rapid melting of the ice. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 15, 2019, photo, a large Iceberg floats away as the sun sets near Kulusuk, Greenland. Greenland is where Earth's refrigerator door is left open, where glaciers dwindle and seas begin to rise. Scientists are hard at work there, trying to understand the alarmingly rapid melting of the ice. For Greenland is where the planet's future is being written. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, a helicopter carrying New York University air and ocean scientist David Holland and his team sits on the ice as they install a radar and GPS at the Helheim glacier, in Greenland. Scientists are hard at work there, trying to understand the alarmingly rapid melting of the ice. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, a helicopter carrying New York University air and ocean scientist David Holland and his team sits on the ice as they install a radar and GPS at the Helheim glacier, in Greenland. Scientists are hard at work there, trying to understand the alarmingly rapid melting of the ice. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, New York University student researchers sit on a rock overlooking the Helheim glacier in Greenland. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, Mugu Utuaq, holds his rifle as he rides in his boat hunting whales near Kulusuk, Greenland. Summer in 2019 is hitting the island hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, a woman stands next to an antenna at an NYU base camp at the Helheim glacier in Greenland. Summer 2019 is hitting the island hard with record-shattering heat and extreme melt. Scientists estimate that by the end of the summer, about 440 billion tons of ice, maybe more, will have melted or calved off Greenland's giant ice sheet. (AP Photo/Felipe Dana)
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David Goldman
FILE - In this Monday, July. 31, 2017 file photo the sun sets over Nuuk, Greenland.
A spokeswoman for Denmark's royal palace says U.S. President Donald Trump's decision to postpone a visit to Denmark next month was "a surprise." Trump announced his decision by tweet after the Danish prime minister dismissed the notion of selling Greenland to the U.S. as "an absurd discussion." (AP Photo/David Goldman, File)
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Felipe Dana
In this Aug. 15, 2019, photo, a boat navigates at night next to icebergs in eastern Greenland.
U.S. President Trump announced his decision to postpone a visit to Denmark by tweet on Tuesday Aug. 20, 2019, after Danish Prime Minister Mette Frederiksen dismissed the notion of selling Greenland to the U.S. as "an absurd discussion." (AP Photo/Felipe Dana)
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Felipe Dana
In this Aug. 16, 2019, photo, New York University student researchers sit on a rock overlooking the Helheim glacier in Greenland.
U.S. President Trump announced his decision to postpone an early September visit to Denmark by tweet Tuesday Aug. 20, 2019, after Danish Prime Minister Mette Frederiksen dismissed the notion of selling Greenland to the U.S. as "an absurd discussion." (AP Photo/Felipe Dana)
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Felipe Dana
Dogs sit outside a home in Kulusuk, Greenland, Thursday, early Aug. 15, 2019. Greenland has been melting faster in the last decade and this summer, it has seen two of the biggest melts on record since 2012. (AP Photo/Felipe Dana)
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Felipe Dana
In this photo taken late Friday, Aug. 16, 2019, homes are illuminated after the sunset in Tasiilaq, Greenland. (AP Photo/Felipe Dana)
