Looked at realistically, so long as extracting energy from the combustion of fossil fuels is cheaper or easier than from non-polluting sources, the fossil fuels will be used until the effects of global warming become unbearable. A heavy carbon tax which reflect the true costs of burning fossil fuels would likely slow the use of these fuels and make green sources of power more competitive. This is unlikely to happen on a large scale in the foreseeable future due to the economic dislocations it would cause.
 
In the meantime, all the world can do is watch the costs of renewable energy fall and hope that there are new sources of non-polluting energy waiting to be discovered that will be so cheap that a rapid movement away from fossil fuels can be accomplished before it is too late.

— Tom Whipple, Peak Oil Review – Dec 14, commenting on the climate change agreement reached by the world leaders in Paris this past weekend