Methane or also known as what is used for Natural Gas, is a widely used fossil fuel. The problem is that there should not be high levels of this released into our atmosphere. I have seen two scientific studies that state that the same ice melt that is shrinking the glaciers, is thawing out the ground where trapped methane gas deposits are now bubbling to the surface. One area is in northern Russia, where they say that it is becoming a serious problem. There is another noted area is in Alaska, where several videos show how the Methane is coming out of the ground. Large amounts of Methane added to our atmosphere will cause accelerated Global Warming.
I do not like to paint a doomsday picture of our future, however it is better that folks understand the concern regarding this and the impact it has on Climate Change.
Here is a detailed youtube video about this topic, this is an older video from 2009, this problem is now worse because the global temperature has risen since then.