How Potent Is Methane?

Two federal agencies this month took steps that would allow the oil and gas industry to release more methane, a greenhouse gas, into the environment. Critics warned that methane is more potent than carbon dioxide at trapping the Earth’s heat, but some gave wildly divergent figures to describe how much more potent.

Sen. Bernie Sanders said methane is 86 times more potent than carbon dioxide, while others, including New Jersey Rep. Frank Pallone, said it was 25 times as potent. So, which is it — 86 or 25 times?

Perhaps surprisingly, both numbers are accurate. The amounts greatly vary, though, because they correspond to different time frames — a detail that often goes unmentioned when these statistics are given.

The values used by Sanders and Pallone are what climatologists refer to as global warming potentials, or GWPs, which is one metric scientists use to compare greenhouse gas potencies. Since these numbers are often given without much explanation of what they actually mean, we’ll dive into some of the details to show the science behind them and the types of assumptions that are baked in.

Sanders and Pallone were responding to the Environmental Protection Agency’s Sept. 11 announcement that it plans to relax regulations designed to limit methane emissions from the oil and gas industry. The public will have 60 days to comment once the proposed rule is published in the Federal Register. 

If the EPA’s change goes through, companies wouldn’t have to monitor for “fugitive emissions,” or leaks, of methane as frequently, and would also