A three-part series about the scientists who are able to move political mountains. World leaders are about to gather in Holland to push through measures to protect the world against global warming. They are doing so because of the warnings of scientists in the Intergovernmental Panel on Climate Change, whose reports foretell dire consequences if we do not stop polluting the atmosphere. Richard Black investigates. Producer Roland Pease. E-MAIL: scirad@bbc.co.uk