A Particularly Ominous Sign of Climate Change

It seems that about once a week I see a news story about how new studies or data show that global warming is happening at a faster rate than previously thought. Yesterday I ran across this:

News Item: “Rapid warming in the Arctic has caused the region to cross a key threshold and become a net emitter of greenhouse gases.” 

The reason is that melting of the permafrost allows methane to seep into the atmosphere. This is the kind of phenomenon that contributes to a runaway effect, wherein even if we were able to cut emissions to zero, global warming would continue by the operation of processes we have set in motion.