Tired of being portrayed as the bad guy in current world-trade talks, the European Community is trying to turn the tables on the U.S. in environmental politics. As the centerpiece of its program for the Earth Summit in Rio de Janeiro this June, the EC has proposed a $10-a-barrel oil tax. Such a levy would aim to slow global warming by curbing hydrocarbon use. EC officials think they have hit upon a no-lose issue. If, as expected, the U.S. rejects the tax idea, Washington will look like an environmental do-nothing at Rio. If the U.S. goes along, the EC will be able to claim credit for leading a radical green initiative.