Friday, January 20, 2023 | 10:48 a.m.
A sharp rise in Greenland temperatures since 1995 shows the giant North American island is 1.5 degrees Celsius warmer than its 20th-century average, its hottest level in more than 1,000 years, according to new data from cylinders. of ice. Until now, ice casts from Greenland — which provide a glimpse into very old temperatures recorded long before the existence of thermometers — have shown no clear indication of global warming in the north central part of the island, its region remoter, at least in comparison with those obtained in other parts of the world. Newly analyzed cylinders of ice, obtained from drilling carried out in 2011, show a drastic increase in temperature in the previous 15 years, according to a study published Wednesday in the journal Nature.
“We continue to (see) temperatures rising between the 1990s and 2011,” said the study’s lead author, Maria Hoerhold, a glaciologist at the Alfred Wegener Institute in Germany. “We now have a clear stamp of global warming.” Years are required to analyze the information stored in the ice cylinders. Hoerhold has cylinders from 2019 but has not finished studying them. She expects the temperature to continue to rise, as Greenland’s ice sheet and glaciers have been melting more rapidly recently. “This is an important finding and corroborates the suspicion that the ‘missing warming’ in the ice casts is due to the fact that (the information in) the casts runs out before strong warming begins,” said the climate scientist. Martin Stendel of the Danish Meteorological Institute, who was not part of the research.
The ice cylinders are used to produce a table of ancient temperatures for Greenland from the year 1000 to 2011. The table shows that temperatures on the island fall slightly during the first 800 years, then fluctuate and gradually rise. , until starting in the 1990s they recorded a sharp and sudden increase. One scientist compared it to a hockey stick, which suddenly has a change in the trajectory of the wood, a description used for other long-term temperature data showing a change in climate.
The increase in temperature after 1995 is much greater than in pre-industrial times before 1850, so the possibility that it was caused by anything other than human-caused climate change is “near zero”, Hoerhold said. The increase in warmth also reflects a sudden increase in the amount of water moving seaward from melting ice in Greenland, the study found.
What had been happening on the island is that natural climate variability — ripples due to an occasional weather system called the “Greenland lock” — had disguised human-caused climate change in the past, Hoerhold noted. But about 25 years ago the warming reached such a magnitude that it could no longer be hidden, he stressed. Past data also showed that Greenland was not warming as fast as the rest of the Arctic, which is warming four times the global average. But the island appears to be closing in on rising temperatures.
For years, data from ice cylinders showed that Greenland behaved a little differently from the Arctic. That was probably due to the blockade of Greenland, Hoerhold said. Other scientists said that as a gigantic land mass, the island was less affected by melting sea ice and other water factors compared to the rest of the Arctic, whose ice lies above the sea.
Hoerhold’s team drilled to remove five new cylinders near the old ones, to match the records already held on the ice. To calculate the temperature, the difference between two different types of oxygen isotopes found in the ice is used, using a formula established in advance that is compared with the observed data.
Hoerhold and outside scientists said the new information about the island’s warming is bad news because its ice cap is melting. In fact, the study concludes with data from 2011, and the following year saw a record melt in Greenland, and it has been losing ice at a high level ever since, he noted.
“We should be very concerned about the warming of northern Greenland because that region has a dozen sleeping giants in the form of wide glaciers that flow into the sea and an ice stream,” said scientist Jason Box of the Danish Meteorological Institute. And when they wake up, they will further thaw the island, he warned. And that means “rising seas that threaten homes, businesses, economies and communities,” said Twila Moon, associate project scientist at the US National Snow and Ice Data Center.
