(Winnipeg) A new report by dozens of international scientists says it’s inevitable that the Arctic will lose all summer sea ice cover at least once in the next generation — and likely much more often.
Updated yesterday at 6:26 p.m.
“We have crossed this threshold,” said Pamela Pearson, one of the main writers of the report on the state of the cryosphere, released Monday at the “COP27” climate conference in Egypt. “The loss of sea ice in summer is now inevitable. »
This loss, which is expected to occur at least once by 2050, signals the transformation of an entire ecosystem from year-round sea ice cover. Its impacts, ranging from worldwide weather disruptions to sea level rise and ocean acidification, are only just beginning to be understood, Professor Pearson reminded. “We don’t know how the system will react. »
The authors of the study draw on the growing convergence of various ice sheet modeling and research on the planet’s climate history. These studies tend to demonstrate what paleoclimatologists have been predicting for decades: ice loss and irreversible sea-level rise could occur faster than previously thought — but also at lower temperatures.
The report concludes that even with global warming limited to 1.5°C – the current goal of the Paris Agreement – the Arctic will sometimes be completely uncovered some summers. At a warming of 1.7°C, this condition would be common at the end of the melt season. And at 2°C, sea ice would disappear from July to October.
The consequences of this disappearance could be disastrous for the plants and animals of the Arctic. Large mammals like polar bears and walruses hunt on pack ice, and the tiny creatures, which form the basis of the Arctic food web, cling to sea ice.
“It’s the coral reef of the Arctic,” summarized Mme Pearson, director of the International Cryosphere Climate Initiative.
Inuit and other northerners across Canada therefore depend on this ecosystem – this “food web” – for food. But they are not the only ones likely to be affected by the loss of sea ice.
Impacts elsewhere in the world
Most scientists now believe the shrinking sea ice is linked to extreme weather events elsewhere in the world, such as floods, as well as longer-term climate disasters, such as droughts, Prof Pearson said. .
In addition, the acidification of the Arctic Ocean is expected to accelerate. This phenomenon, caused when the oceans absorb more carbon dioxide from the atmosphere, is already having an effect on shellfish.
Warmer northern seas will also likely increase emissions of methane, a very potent greenhouse gas, which will be released by melting permafrost.
Global warming will also likely accelerate the melting of the Greenland ice sheet, according to the report. Even at a warming of 1.5°C, sea levels are expected to rise by at least one meter over the next century, it is estimated.
The warning signs are there, said Mme Pearson. It rained in Antarctica last March, when temperatures were 40°C above normal. The melting of the Greenland ice sheet peaked in September for the first time ever. The Alps have lost more than 5% of their ice in a single summer.
As the “COP 27” conference begins in the Egyptian seaside resort of Sharm el-Sheikh, Mme Pearson believes that international leaders have a lot on their plate. Several countries have pledged to be carbon neutral by 2050, but that means they will have to halve their emissions by 2030, Ms.me Pearson.
“We don’t see it in reality yet. Many of these promises are really vague. No country in the world is on track to halving its emissions,” she says.
It’s time for countries to roll up their sleeves, launches Mme Pearson. “The ice doesn’t care about your targets. »