While this article is encouraging when looking at the title, they are still pushing that “ice-free summer” meme.
A late-winter expansion of Arctic sea ice is a good example of ice-forming dynamics that could keep the Arctic from hitting a “tipping point” in the near future.
Some scientists have predicted that rising temperatures could create a runaway feedback loop in the Arctic. Sunlight-reflecting ice sheets would give way to sunlight-absorbing water, driving up temperatures and melting even more ice. The Arctic climate would change so dramatically that winter ice couldn’t form again, producing planet-wide ripples in weather patterns.
But some research suggests that other, previously underappreciated forces may stabilize the melt before it’s complete. The Arctic will soon be ice-free in summer, and winter ice will decline, but it won’t suddenly become permanently ice-free.
“Everyone thought there would be a tipping point,” said Dirk Notz, a Max Planck Institute climate scientist. “But that’s too simple.”
Tipping-point evidence is stronger for western Antarctica than Greenland, said Notz. But even the absence of a tipping point wouldn’t necessarily be reassuring. “It doesn’t mean Greenland won’t melt away,” he said. “It just means it will happen gradually.”
Polar Sea Ice
Dwindling Arctic sea ice and crumbling Antarctic ice sheets are now a common sight. Whether they signal an impending tip, with rapid melts causing Earth’s seas to inundate heavily-populated coastal plains, is debated.
The process appears to accelerate itself: Warming ice melts, which exposes darker areas, causing local temperatures to rise further. But in the Arctic, another feedback may stabilize the ice, wrote Max Planck Institute meteorologist Dirk Notz in PNAS. Though most of the ice “will disappear during summer,” much of it will re-freeze in the winter. Arctic sea ice loss “is likely to be reversible if the climate were to become cooler again.”
But Notz is less optimistic about Antarctic sea ice, its undersides heated by eddying Southern Ocean currents. And the West Antarctic and Greenland ice sheets have shrunk suddenly at least twice in the last several million years, a behavior that’s backed up by climate models. It’s “well possible that a tipping point exists for a possible collapse” for those sheets, wrote Notz. It could “render the loss of ice sheets and the accompanying sea-level rise unstoppable beyond a certain amount of warming.”
From a UC Davis press release
Though, my favorite environmental tipping sign is this one :