The window has closed to prevent the melting of summer Arctic Sea ice due to human-caused climate change, according to a study published Tuesday in the journal Nature Communications. The research indicates that even under a scenario where carbon emissions are sharply curtailed, the Arctic will be “practically” ice-free in September by the middle of the 21st century. The study’s projection goes even further than the warning issued in 2021 by the United Nations’ Intergovernmental Panel on Climate Change (IPCC), which determined there is still a chance to save the summer ice in a scenario where warming is kept below...