As Shell Gambles on Gas, Leaks Loom Over Clean Credentials

After spending $50 billion on the world’s biggest bet on natural gas, Royal Dutch Shell Plc is at the forefront of Big Oil’s efforts to clean up its act. But what if the constant, insidious leaks of gas into the atmosphere actually make the fuel more polluting than coal?

Methane, the main component in natural gas, can seep into the air at various points between extraction and delivery. Trapping more heat than carbon dioxide, it’s a potent contributor to global warming. Yet credible data on the volumes released is scarce, and that’s spurring pressure from investors.

“This is such an ...