German officials are warning of an environmental disaster in the Baltic Sea, after the Nord Stream pipelines that carry Russian gas to terminals in Europe ruptured on Monday in what U.S. and EU officials have called an “act of sabotage.” Swedish scientists say they detected two large underwater explosions shortly before pressure through the pipelines plummeted. One of the leaks is producing a nearly half-mile-wide pool of bubbling seawater. Officials estimate some 300,000 metric tons of methane have vented into the atmosphere from that site alone, which would put it among the worst gas leaks in history. Methane is a significant contributor to global heating. It can linger in the atmosphere for decades before breaking down, with about 80 times the warming power of carbon dioxide.