Iceless September Predicted for the Arctic in the Future

Arctic sea ice could disappear completely through September each summer if average global temperatures increase by as little as two degrees, according to a new study by the University of Cincinnati. 

Historically, September is the month that sees the Arctic Ocean’s least ice cover during the year after the short polar summer. Ice recedes from June to September, and then in September it begins to grow again in a seasonal cycle. The less summer sea ice the Arctic has, the longer it takes for the Arctic Ocean to ice back over for the polar winter. That could spell bad news for Arctic wildlife such as seals and polar bears that rely on sea ice for survival.

Limiting warming to two degrees is the stated goal of the 2009 Paris Agreement, the international effort to curb carbon emissions to address warming, but limiting the warming to two degrees may not be sufficient to prevent an ice-free Arctic Ocean, say the researchers.

The researchers applied the new statistical method to climate model projections of the 21st century. Using these models, the authors found at least a six percent probability that summer sea ice in the Arctic Ocean will disappear with warming of 1.5 degrees above pre-industrial levels. At two degrees, the likelihood increases to 28 percent. 

Won Chang, a study co-author and University of Cincinnati assistant professor of mathematics, said: “Climate scientists are very honest,” he said. “We try to be as transparent as possible about the amount of uncertainty we have and lay out all of our assumptions and emphasize that when we say there is a possibility, we quantify it in the form of a probability.”

He thinks public perceptions about climate change might depend on where you live. “Most South Koreans don’t question climate change, not because they’re more scientific, but because they can see the effects firsthand,” Chang said. “My hometown is a southern city called Daegu. It’s about the size of Cincinnati. And it was famous for growing a delicious apple. But now they can’t grow the apples there. The orchards are gone. It’s just too hot. Now they grow them farther north.”

While the researchers only tested the new approach on climate models, they are eager to see if the technique can be applied to other fields, such as stock market predictions, plane accident investigations and medical research.