According to Greenland ice record, 2001-2011 was the hottest decade in the past 1,000 years: study

Rivers of meltwater (Greenland's ice sheet) (Alfred-Wegener-Institut / S. Kipfstuhl)

According to the ice record of Greenland’s massive ice sheet, 2001-2011 was the hottest decade in the past 1,000 years — and new data shows there’s clear evidence that recent warming is increasing at a rate far outside of regular climate fluctuations.

The Greenland ice sheet is the glacier covering around 80 per cent of inland Greenland, and it’s been around for millions of years, providing a frozen snapshot of global temperature through history in its layers of ice.

Researchers have been drilling down and analyzing ice cores from the Greenland ice sheet for years, but a of lack long-term data has made it difficult to isolate signs of global warming versus the Earth’s natural variability in temperature.

However, new data shows that global warming has definitely hit Greenland, according to a study published Wednesday in the peer-reviewed journal Nature.

“The time series we recovered from ice cores now continuously covers more than 1,000 years, from year 1000 to 2011,” Maria Hörhold, a glaciologist with the Alfred Wegener Institute and lead author of the study, said in a press release.

“This data shows that the warming in 2001 to 2011 clearly differs from natural variations during the past 1,000 years. Although grimly expected in the light of global warming, we were surprised by how evident this difference really was.”

The temperatures recorded between 2001-2011 were, on average, 1.5 degrees Celsius warmer than those of the twentieth century as a whole, the study found, and 1.7 degrees Celsius warmer than the 1961-1990 period.

They also found that there was increased meltwater run-off along with the disproportionate warming of recent years, a warning sign that Greenland’s loss of mass through its ice could be starting to accelerate.

Greenland’s ice sheet is the second largest mass of ice globally, second only to the ice covering Antarctica, containing around three million cubic kilometres of frozen water. Not only does the presence of this massive ice sheet play a key role in the planet’s overall climate, but it has the ability to cause a huge shift in sea level if it were to melt.

If global emission rates do not change, this single ice sheet is estimated to add 50 centimetres to the sea level worldwide by 2100.

Currently 267 million people worldwide live on land less than two metres above sea level, according to a 2021 study.

The Earth has gone through big shifts in global temperature before due to natural variability, something which is evident in the ice record. This new study noticed that there was an overall cooling trend from 1000-1800, followed by a warming trend from 1800 onwards.

But these long term trends make it even more clear that the warming that has taken place over the last couple decades is escalating at a rate that is far beyond that natural warming seen since 1800.

“Despite the pronounced natural variability that we observe, this high temperature value is exceptional in the context of the past 1,000  years,” study authors wrote.

Researchers extracted ice cores in the high-elevation, remote areas of central and north Greenland to update their datasets during the 2011-2012 winter season. Temperatures were established by measuring the concentration of oxygen isotopes within the ice, which change depending what temperature it was at the moment that ice was formed.

They also recreated meltwater patterns to measure how the temperature inland was affecting the increasing levels of meltwater that have been observed since the 2000s.

They compared the temperatures to data from a regional climate model for the years 1871-2001 and satellite observations of the receding edges of the ice sheet from 2002-2021.

It showed that there was a strong connection between the temperature even at high elevations in Greenland and the number and intensity of meltwater run-off events.

“We were amazed to see how closely temperatures inland are connected to Greenland-wide meltwater drainage – which, after all, occurs in low-elevation areas along the rim of the ice sheet near the coast,” Hörhold said.

The study added that under further global warming, the rate at which the ice sheet is melting is expected to increase.