The absence of key players like Obama has cast a shadow, as has the relative failure of the 1997 "Kyoto Protocol" on limiting greenhouse gases, which was set in motion at the 1992 Rio summit.

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The dispute was one reason for the failure of The Hague talks on the Kyoto Protocol last November.

BBC: EU pushes for Kyoto compromise

Another anti-economic aspect of the Kyoto protocol, in addition to its silence on trading, was its failure to put a cap on the costs of abatement: countries undertook to meet their targets regardless.

ECONOMIST: Economics focus

The union has interviewed two of the 18 teachers, and the accusations generally involve improperly coaching students and failure to follow testing protocol, he said.

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