A new report from dozens of international scientists says it’s inevitable the Arctic will lose its entire summer sea cover at least once over the next generation and probably a lot more often than that. “It’s a threshold tipped,” said Pamela Pearson, one of the main editors of the State of the Cryosphere report delivered Monday at the COP27 climate conference in Egypt, montrealgazette.com informs.

“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 ice cover. Its other effects, from disrupted weather around the globe to rising sea levels and ocean acidification, are barely beginning to be understood, Pearson said.

“The consequences are unpredictable. We don’t know how the system will respond.”

The authors draw on the growing convergence of ice sheet models and research into Earth’s ancient climate. That convergence points to what paleoclimatologists have warned for decades — that ice loss and irreversible sea-level rise may be occurring faster and at lower temperatures than previously forecast.

The report concludes that even with 1.5 C of warming — the current target — the Arctic will occasionally be entirely open on some years. At 1.7 C, that condition would be common by the end of the melt season. At 2 C, ice would be gone from July through October.

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

“It’s the coral reef of the Arctic,” said Pearson, director of the International Cryosphere Climate Initiative.