The rapid loss of Antarctic sea ice brings grim scenarios into view

W hen the area near Antarctica covered by sea ice fell to 1.8m km² (800,000 square miles) on February 19th—the smallest extent since satellite-based data became available in 1978—few climatologists were surprised. Such records fall frequently in a warming world, as they did at the same time of year in 2017 and 2022. In March ice cover in the Antarctic began bouncing back at a rate of 70,000 km² per day, close to the historical average.

However, between April and June the ice did not recover as expected, with a growth rate around 15% lower than normal. And at the start of July its edge turned south, receding at a time when it should have been advancing rapidly. By July 6th Antarctic sea ice covered just 12m km², roughly as large as Brazil and India put together. Compared with the average for that date in 1981-2010, its area was 2.84m km² smaller—a gap as large as Argentina or Kazakhstan.