No Tipping Points for Arctic Sea Ice Loss

A growing body of scientific evidence has led researchers to believe that in a warmer climate there will be no “tipping point” beyond which the Arctic sea ice cannot recover if temperatures start to decrease. Added to this is new research out of the University of Washington which suggests that even if the planet warmed enough to melt all polar sea ice, it could still recover if the temperatures cooled again.

Researchers from the University of Washington used one of two computer-generated global climate models to simulate the growth and subsequent decrease of carbon dioxide in the atmosphere.

The model currently predicts that we will completely lose all September Arctic sea ice by the middle of this century.

However, it will take almost another two hundred years before the Arctic is devoid of sea ice during winter.

“We expected the sea ice to be completely gone in winter at four times the current level of carbon dioxide but we had to raise it by more than eight times,” said Cecilia Bitz, a UW associate professor of atmospheric sciences.

“All that carbon dioxide made a very, very warm planet. It was about 6 degrees Celsius (11 degrees Fahrenheit) warmer than it is now, which caused the Arctic to be completely free of sea ice in winter.”

The scientists used the model to increase atmospheric carbon dioxide by one percent each year, which resulted in doubling the levels of greenhouse gasses approximately every 70 years. The model started with an atmospheric carbon dioxide level of 355 parts per million, and by the time the sea ice was completely gone during winter it had reached levels greater than 3,100 parts per million.

They then reduced the levels of carbon dioxide by one percent each year until temperatures were back to something similar to what they are today. However, this sort of dramatic decrease could only be managed by naturally or mechanically drawing the carbon dioxide out of the atmosphere, rather than simply limiting the burning of fossil fuels.

“It is really hard to turn carbon dioxide down in reality like we did in the model. It’s just an exercise, but it’s a useful one to explore the physics of the system.”

Bitz was careful to note that, while a lack of a tipping point may be good news, it does not diminish the need for concern and action in decreasing the levels of greenhouse gas levels. “Climate change doesn’t have to exhibit exotic phenomena to be dangerous,” Bitz said, noting that the current loss of sea ice has already started to have a harmful impact on species such as polar bears and to some people who have been forced to relocate their homes.

“The sea ice cover will continue to shrink so long as the Earth continues to warm,” she said. “We don’t have to hypothesize dramatic phenomena such as tipping points for this situation to become challenging.”

Source: University of Washington
Image Source: NASA Goddard Space Flight Center

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