5. What about in the really, really long term?
One of the big questions is how much warming will it take to melt the Greenland Ice Sheet, which contains enough water to raise sea levels by 7 meters (23 feet). This is an incredibly difficult question to answer, but current research shows it is likely between 1 degree and 4 degrees warming, compared to pre-industrial averages. If 2 degrees is enough to melt the Greenland Ice Sheet, for instance, it could mean sea levels would rise much higher and faster than current projections show. A total melting of Greenland's ice likely would take thousands of years, though.