Talks at the U.N. climate summit in Paris have been extended into the weekend as representatives from nearly 200 nations work to finalize a global accord. A draft text released Thursday includes the voluntary target of limiting global warming to 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, above pre-industrial levels. Including the 1.5 degrees Celsius target meets a key demand of low-lying and vulnerable nations. Environmentalists and civil society have criticized its voluntary nature along with many other provisions, and there remain over 50 points of disagreement between nations negotiating the draft.