The world has "little time before the window of opportunity to stay within two degrees Celsius (3.6 degrees Fahrenheit) of warming closes," Rajendra Pachauri, head of the UN's climate panel, said Sunday.
"To keep a good chance of staying below 2 C, and at manageable costs, our (carbon) emissions should drop by 40 to 70 percent globally between 2010 and 2050, falling to zero or below by 2100," Pachauri said as he presented the biggest overview on climate change in seven years.