Methane Levels Are Rising, and Scientists Don’t Know Why

Carbon dioxide is climate change’s villainous star. But methane, an even more potent greenhouse gas, is CO2’s lesser-known evil twin. Researchers now find methane levels in the atmosphere are on an escalating upward trend. That’s a problem because emission scenarios that limit global warming to 2 degrees Celsius assume methane levels will drop over the next 30 years.