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Ice Loss Accelerates Warming

Image of Earth temperatures

The 28-year temperature trend for the autumn season. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio

By Stephen Luntz

Climatologists believe they have confirmed what has been long suspected: the rapid loss of sea-ice from the Arctic is a result of a feedback cycle where global warming causes ice loss, which in turn causes more local warming.

Dr James Screen of the University of Melbourne’s School of Earth Sciences notes that the Arctic has experienced twice the global average warming in recent years. Theories to explain this include changes in cloud cover and the transportation of warmer air to the poles. However, Screen has demonstrated a tight correlation between the warming and loss of sea-ice, a finding significant enough to win publication in Nature.

“We’re saying it’s a two-way process,” says Screen. “The warming causes melting, which in turn causes more warming, and that leads to more ice loss.” Although the cycle is interrupted each year by winter, Screen says the ice that forms is thinner than was there before the recent warm summers and is “more susceptible to melting the next year”.

Only a sustained period of local cooling can interrupt this cycle, which Screen avoids calling bad news “depending on whether you think an ice-free summer Arctic is a good thing or not”. Nevertheless he agrees it suggests that more melting is in store.

The research relies on a new dataset that Screen says “cleverly combines observations from the few meteorological stations in the area, satellite data and any boats and planes that have gone through”.

The research was focused on the Arctic only. Screen says that ozone depletion has shielded the Antarctic from similar ice loss.

Screen has personally felt the effect of volcanic eruptions close to the North Pole, with his UK-based parents kept in Australia a week longer than expected when they came to visit him. However, while volcanic influences are outside his area of expertise, he says his understanding is that the Eyjafjallajökull eruption in Iceland has not been large enough to have a global effect, and the cloud drift has taken it away from the Arctic, preventing regional impact.