Once the gas made it to the ocean surface, it could have escaped into the atmosphere, triggering terrestrial extinction, Kump says. “Poisonous clouds of hydrogen sulfide wafting around the continents would have killed animals and vegetation,” he says. The gas also could have damaged the planet’s ozone layer letting destructive radiation reach Earth’s surface.
Methane, a potent greenhouse gas, have been constant for five years after two centuries of steady increases. Scientists do not know why the pattern of increase has stopped.
This is from the Department of the interior, USGS. their findings show that humans generate a significantly higher amount of greenhouse gases than volcanoes.