My Way News - Methane seen as growing climate risk
My Way News reports: "Historically, methane concentrations in the world's atmosphere have ranged between 0.3 and 0.4 parts per million in cool periods to 0.6 to 0.7 in warm periods. Current methane concentrations in the Arctic average about 1.85 parts per million, the scientists said, the highest in 400,000 years."