Vast stretches of Earth’s northern latitudes are on fire right now. Hot weather has engulfed a huge portion of the Arctic, from Alaska to Greenland to Siberia. That’s helped create conditions ripe for wildfires, including some truly massive ones burning in remote parts of the region that are being seen by satellites. All told, northern fires released as much carbon dioxide in June as the entire country of Sweden does in a year, according to data crunched by the European Union’s Copernicus program. The agency said the wildfire activity is “unprecedented” amidst what was, incidentally, the hottest June ever recorded...