Currently we're at .8 degrees Celsius above the preindustrial age. The effects described for 2 degrees in the above documentary are already happening (e.g. bark beetle, melting ice sheets), so all the predictions have been too conservative.
If we continue, business as usual, Earth will have warmed by up to 1.5 degrees Celsius by 2025. Hey guys, that's only 15 years... and means that the warming will be nearly double what it is now. If 2010 is any predictor of how bad it can be, we're in for big trouble.
This is beyond an abrupt change, it is violent.
Continuing with a business-as-usual approach to energy use into the foreseeable future could foster a 4 degree C warming, perhaps as early as the 2060s, a package of new papers concludes.World could heat up 4 degrees C in 50 years
Such a dramatic temperature increase would be expected to trigger extensive, recurring droughts in some parts of the world, flood coastlines as sea levels rise and drastically alter the types of crops that can survive where lands remain arable, notes Mark New of the University of Oxford in England. New contributed to several of the 11 papers in the Philosophical Transactions of the Royal Society A. The journal issue, officially dated January 13, 2011, has been posted early online to coincide with the November 29 start in Cancun, Mexico of the United Nations Framework Convention on Climate Change.
Also see (and read the comments too)
Royal Society special issue details ‘hellish vision’ of 7°F (4°C) world — which we may face in the 2060s!
However there are technologies that could save us even if we won't save ourselves.