Sea ice data does not disprove warming in Antarctica
"We are constantly being lied too (sic)," says a May 6, 2025 post on Threads.
The post shares an image juxtaposing two charts measuring sea ice extent. One is from December 24, 1979, while the other from December 24, 2024.
"Antarctic sea ice extent is 17% higher today than it was in 1979," text under the charts reads.
Image
A screenshot of a Threads post taken on May 20, 2025
Similar claims also appeared on other platforms, including Instagram and X.
Narratives seeking to deny the impact of climate change on the Arctic and Antarctic -- the polar regions surrounding the North and South poles -- often rely on sea ice data to make misleading claims.
In this case, the charts shared online come from the National Snow and Ice Data Center (NSIDC). AFP retrieved exact matches for them from the NSIDC online archives (here and here).
But their side-by-side comparison amounts to "a classic case of cherry picking," said Walt Meier, senior research scientist at the NSIDC.
"Looking at single days from two years does not give useful information about trends or the response of sea ice to warming," Meier said May 14.
Cherry-picked data
The NSIDC says on its website that sea ice data has been repeatedly misused to spread myths about global warming (archived here). Generally, scientists look at decade-long trends for "sea ice extent," a term referring to the total area of the ocean where at least 15 percent of the surface is frozen.
Image
An image taken from the National Snow and Ice Data Center's (NSIDC) archives shows sea ice extent in Antarctica on December 24, 1979 (National Snow and Ice Data Center)
The measurements taken on December 24, 1979 and December 24, 2024 do show a difference in sea ice cover, the agency said, but it is about a 12 percent increase -- not 17 percent.
Comparing most other dates would have left a different impression.
"From 1 January through 13 December, the 2024 extent was below 1979 levels, by over 1 million square kilometers at times," Meier said, noting that this equates to an area roughly the size of Egypt.
"Only during 14-31 December were 2024 extents higher than 1979," he added.
Antarctica's summer months, from December to February, naturally show greater shifts of sea ice extent because of warmer temperatures and longer hours of sunlight.
That means a small change in the timing of the retreat of ice -- and when exactly melt season starts -- can quickly and greatly shift its extent in one December relative to another, Meier explained.
Across the whole of 2024, warming was observed and sea ice extent measured lower than the 1979 annual average by about 11 percent, according to NSIDC data.
According to the National Oceanic and Atmospheric Administration, Antarctic sea ice extent hit its second lowest annual minimum in 2024 since monitoring started in 1979, with the year 2025 likely to tie such a record (archived here and here).
Potential 'regime shift'
Dramatic shifts in climate have already occurred in the Antarctic Peninsula, the part of Antarctica farthest from the South Pole. The peninsula is warming at a rate five times faster than the global average -- and faster than anywhere else within the Southern Hemisphere (archived here).
Yet continent-wide patterns of temperature change remain uncertain, scientists say.
Unlike the Arctic, where sea ice extent has been consistently decreasing across all areas and seasons since records started, Antarctica's sea ice lacks a defined long-term decline (archived here).
"The Antarctic sea ice is thin and open to the ocean, so it has much more variability and thus the global warming signal is not as evident," Meier said.
The last decade has shown more extreme fluctuations, which scientists say could indicate a "regime shift" into a new low-extent state, possibly due to warmer oceans (archived here and here).
Both polar oceans are warming, with the "Southern Ocean being disproportionately and increasingly important in global ocean heat increase," according to the Intergovernmental Panel on Climate Change, the leading international consortium of climate scientists (archived here).
Samantha Burgess of the European Centre for Medium-Range Weather Forecasts, which runs the Copernicus climate monitor, added in a February 2025 report: "One of the consequences of a warmer world is melting sea ice, and the record or near-record low sea ice cover at both poles has pushed global sea ice cover to an all-time minimum."
When highly reflective snow and ice give way to dark blue ocean, the sun radiation that once used to bounce back into space is instead absorbed by water, accelerating the pace of global warming in a feedback loop.
Decreased ice cover also has serious and rapid impacts on ecosystems, such as the survival of penguins and their habitats (archived here).
AFP has debunked other claims about the effects of global warming at the Poles, including here.
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