A new study has found that as much as half of the decline in Arctic sea ice over the last several decades was due to natural causes, rather than human interaction.

And a New Zealand climate expert says the findings show how variability in the Arctic and Antarctica might not be so different after all.

Although human interaction is still a major factor in the decline, the study shows the sea ice is less sensitive to our interactions than initially thought.

"It is well recognised that recent Arctic sea-ice decline has both natural and anthropogenic drivers, but their relative importance is poorly known," said the research, published online in Nature Climate Change.

The study was conducted by Qinghua Ding from the University of California, and his colleagues.
It focused on atmospheric circulation in the summer months and how it influenced the extent of Arctic summer sea ice in September.

"We have provided a plausible mechanism for how circulation changes can impact Arctic sea ice, but it is difficult to determine causality with observational evidence alone, because of the feedbacks between sea ice and the atmosphere," the study said.

Researchers were able to conduct several model experiments to show how high-latitude circulation impacted sea ice.
The researchers found 30 to 50 per cent of the overall decline in September Arctic sea ice since 1979 could be accounted for by natural variability.