Climate conference hears loss of Arctic summer sea ice now inevitable by 2050

A new report from dozens of international scientists says it'sinevitable the Arctic will lose its entire summer sea cover at leastonce over the next generation and probably a lot more often thanthat.

"It's a threshold tipped," said Pamela Pearson, one of the maineditors of the State of the Cryosphere report delivered Monday atthe COP27 climate conference in Egypt.

"Loss of summer sea ice is now inevitable."

The loss, expected to happen at least once by 2050, spells the end of an entire ecosystem that has evolved for year-round icecover. Its other effects, from disrupted weather around the globe torising sea levels and ocean acidification, are barely beginning tobe understood, Pearson said.

"The consequences are unpredictable. We don't know how thesystem will respond."

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The authors draw on the growing convergence of ice sheet modelsand research into Earth's ancient climate. That convergence pointsto what paleoclimatologists have warned for decades that ice lossand irreversible sea-level rise may be occurring faster and at lowertemperatures than previously forecast.

The report concludes that even with 1.5 C of warming thecurrent target the Arctic will occasionally be entirely open onsome years. At 1.7 C, that condition would be common by the end ofthe melt season. At 2 C, ice would be gone from July throughOctober.

The consequences are likely to be dire for Arctic plants andanimals. Animals such as polar bears and walruses hunt from sea iceand the tiny creatures that form the base of the Arctic food webhang from it.

"It's the coral reef of the Arctic," said Pearson, director ofthe International Cryosphere Climate Initiative.

Inuit and other northerners from across Canada depend on thatecosystem for food.

However, they aren't the only ones likely to be affected by theloss.

Most scientists now believe shrinking sea ice is connected toextreme weather events such as floods, as well as slow-motionclimate disasters such droughts, Pearson said.

As well, the acidification of the Arctic Ocean is likely to speedup. That phenomenon, caused when oceans absorb more carbon dioxidefrom an atmosphere where its levels are enriched, is already havingan effect on shellfish.

Warmer northern seas are likely to increase the amount of methane a potent greenhouse gas being released from thawing permafrost.

They will also likely speed up the melting of the Greenland icecap, the report says. Even at 1.5 C of warming, sea levels arelikely to rise at least a metre over the coming century.

The warning signs are there, Pearson said.

It rained in Antarctica last March, when temperatures were 40 Cabove normal. Melting of the Greenland ice cap spiked in Septemberfor the first time ever. The Alps lost more than five per cent oftheir glacial ice in a single summer.

As the COP 27 conference gears up, Pearson said internationalleaders have a lot of work ahead of them.

Many countries have pledged to be carbon-neutral by 2050, but shepoints out that means they must halve their carbon emissions by2030.

"We're not seeing that yet in reality. A lot of those pledgesare really vague. There's no country in the world that is on trackto halve their emissions."

Time to get to work, Pearson suggested.

"The ice doesn't care about your pledges."