Though researchers don’t know why methane levels are currently rising, the fossil fuel industry was likely to blame in the past. (Credit: Nick Stubbs/Shutterstock)

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 lev