A tax on upstream carbon sources is one easy way to put a price on carbon emissions, although some countries may wish to use other methods, such as emissions trading schemes.

The White House's unexpected unveiling of a tax on bank liabilities and a ban on proprietary trading did not help matters, complicating discussions at a delicate time.

That's sending major indexes lower on the final day of trading as investors lock in gains, or sell underperforming stocks to reap a tax benefit.