As Time succinctly put it,

The language of science, like that of the United Nations, is by nature cautious and measured. That makes the dire tone of the just-released final report from the fourth assessment of the U.N.’s Intergovernmental Panel on Climate Change (IPCC), a network of thousands of international scientists, all the more striking. Global warming is “unequivocal.” Climate change will bring “abrupt and irreversible changes.” The report, a synthesis for politicians culled from three other IPCC panels convened throughout the year, read like what it is: a final warning to humanity.

The full piece is here.