Feedback loops, as per a microphone getting too close to a speaker resulting in a piercing loud howl, are powerful entities whereby outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:
"Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole."  , something that's happening to earth regarding the melting of ice caused by increased CO2 levels trapping in more heat, which, in turn, reduces the all important albedo which, in terms of the feedback loop effect, accelerates the process of turning the arctic and antarctic from a reflective surface to a heat sink, thus accelerating climate change at a rate unforeseen by climatologists, until now.
To come to their findings, the authors used a mixture of paleoclimate records, computer models, and observations of current rates of sea level rise, but “the real world is moving somewhat faster than the model,” Hansen says.
It gets better.
If you truly understand global warming, then you know it's all about the ice. That's what matters. Planet Earth has not always had great ice sheets at the poles, of the sort that currently exist atop Greenland and Antarctica. In other periods, much of that water has instead been in liquid form, in the oceans—and the oceans have been much higher.
How much? According to the National Academy of Sciences, the globe's great ice sheets contain enough frozen water to raise sea levels worldwide by more than 60 meters. That's about 200 feet. And it makes all the sea level rise that we've seen so far due to global warming appear piddly and insignificant.
That's why scientists have long feared a day like this would come. Two new scientific papers, in the journals Science and Geophysical Research Letters, report that major glaciers that are part of the West Antarctic Ice Sheet appear to have become irrevocably destabilized. The whole process may still play out on the scale of centuries, but due to the particular dynamics of this ice sheet, the collapse of these major glaciers now "appears unstoppable," according to NASA (whose researchers are behind one of the two studies).
BRT has talked about the 900 lb GW gorilla in numerous articles including the one titled Albedo , a blurb describing just how powerful a cooling agent ice truly is, something earth is losing 24/7 as we move further into the 21st century.