In late March, a delegation of California government officials arrived in Brussels on a most unusual mission. Governor Arnold Schwarzenegger had sent them to meet their counterparts at the European Commission and explore whether his state could join one of Europe’s most ambitious and controversial projects: the emissions trading scheme.

Both sides emerged from the talks feeling optimistic that a deal was possible to link the European Union regime with a state that itself counts among the biggest emitters of carbon dioxide in the world. “We hope that California will be able in the near future to be the first non-European region that would join the emissions trading system,” a Commission official said.