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A warming world could reduce levels of Antarctic sea-ice, but the current dramatic reduction could also be due to local weather conditions or ocean currents, explains Dr Caroline Holmes at the British Antarctic Survey.
She emphasises it is not just a record being broken - it is being smashed by a long way.
"This is nothing like anything we've seen before in July. It's 10% lower than the previous low, which is huge."
She calls it "another sign that we don't really understand the pace of change".
Scientists believed that global warming would affect Antarctic sea-ice at some point, but until 2015 it bucked the global trend for other oceans, Dr Holmes says.
"You can say that we've fallen off a cliff, but we don't know what's at the bottom of the cliff here," she says.
"I think this has taken us by surprise in terms of the speed of which has happened. It's definitely not the best case scenario that we were looking at - it's closer to the worst case," she says.
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