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Scientists tracking Antarctic sea ice levels spotted a big shift in 2023

LEILA FADEL, HOST:

For decades, scientists have gathered evidence that climate change is melting sea ice in the Arctic. But Antarctica has been this weird outlier. The region's sea ice melt hasn't been so dramatic. That's because the two places are quite literally polar opposites. The Arctic up north is an ocean surrounded by land. The Antarctic in the South is land surrounded by ocean.

CAROLINE HOLMES: It's a very different setup.

FADEL: That's Caroline Holmes. She's a polar climate scientist at the British Antarctic Survey. Scientists like her have been tracking Antarctic sea ice levels by satellite for 45 years, and they spotted a big shift in 2023.

HOLMES: Last year, there were loads of dramatic climate stories going on. And one of those was that sea ice in the Antarctic was really dramatically low in Antarctic winter. So that's our summer, Antarctic winter.

FADEL: Antarctic sea ice plummeted to the lowest point on record, but it wasn't immediately clear whether human activity caused that. There's a lot going on in the Antarctic climate, Holmes says.

HOLMES: The Antarctic is really variable. We know things like winds, temperatures around Antarctica are some of the most variable places on Earth. And because of that, you could get lots of naturally caused variation that are kind of masking anything that's going on with climate change.

FADEL: So Holmes and her colleagues at the British Antarctic Survey put together some calculations. They used computer modeling to determine how unusual it is over the long term for the Antarctic to lose that much sea ice.

HOLMES: We found that this is a really rare thing. I mean, we knew it was rare because it hadn't happened before in our lifetimes, but we showed using computing that it really, really, really was a really, really extremely rare event.

FADEL: That suggests such a major ice loss isn't only a product of shifting wind patterns or ocean currents. Now there's much clearer evidence that climate change is playing a role.

HOLMES: We found that it would only have happened about once in 2,600 years without any kind of climate change according to the models. And then with kind of quite strong climate change, so the kind of thing we will see over the next 80 years, it becomes about four times more likely.

FADEL: Fixing the problem comes down to - you probably guessed it - reducing greenhouse gases. Caroline Holmes says that until then, reliance on fossil fuels will continue to shape the Antarctic even if the effects don't show up right away. Transcript provided by NPR, Copyright NPR.

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