Jeffrey Sachs, director of the earth institute at the Columbia University, spoke to FRANCE 24 at the COP21 climate conference in Paris. He is cynical about the ambition related to a potential agreement.'There will be a deal' to limit global warming below 2C, he says, but solutions and commitments to reach this target will be too vague. He also claims that his country, the United States, and more specifically Congress, are not ambitious enough on this issue.