At the United Nations, a group of leading scientists made a new appeal Tuesday for immediate action on global warming. This is Dr. John Holdren, a member of the scientific expert group on climate change and sustainable development.

Dr. John Holdren: “Our specific conclusions are that if the world were to go past the point of an increase above pre-industrial temperatures greater than two to two-and-a-half degrees Celsius, we would be in a regime where the danger of intolerable and unmanageable impacts on human well-being would rise very rapidly. And it is therefore essential, in our view, that the world agree on a target on not exceeding two to two-and-a-half degrees Celsius above pre-industrial. It is important to understand we’re already at about point-eight degrees Celsius above pre-industrial.”