COPENHAGEN, Denmark -- Denmark pushed the button Wednesday on an ambitious project that aims to bury vast amounts of planet-heating carbon dioxide gas beneath the North Sea floor, in the hope that it can help the Nordic nation and others meet climate targets. Denmark's Crown Prince Frederik gave the symbolic order to begin pumping CO2 into the depleted reservoir of the Nini West oil field, 50 years after his father Prince Henrik celebrated the start of oil and gas exploration off the Danish coast. “It gives me great pleasure today to be able to reverse the traffic in the pipes...