Prime Minister Justin Trudeau came to Vancouver for climate change talks with provincial and territorial leaders with one ambitious goal: a national carbon tax. What the prime minister has walked away with is a commitment from the premiers to spend the next six months discussing how such a tax is possible.

Each province has signed on for some sort of carbon pricing, but how that will work is still unclear. That's where B.C. Premier Christy Clark comes in.  

Clark, who inherited the carbon tax from Gordon Campbell, is now its de-facto spokesperson and will be the one having to rally her colleagues around the currently unpopular idea

She can argue her province has had success with a $30 per tonne tax, without hindering economic growth.

"We have proven over eight long years of doing this, that having a carbon tax doesn't have to hurt the economy," said Clark. "We are the fastest growing economy in the country while we have had the highest, broadest carbon tax. Why? Because it has been totally revenue neutral."

Clark argues B.C.'s revenue-neutral model — where money collected is returned in the form of a reduction in other taxes — will work elsewhere.

"Every carbon tax in the country needs to be revenue neutral for individuals. I don't think you can build support for environmental protections that make people poorer," says Clark. "You can only build consensus around these type of changes if it makes people wealthier, which is what we have done in B.C."

On the surface, it sounds like a compelling pitch. But on a political level carbon taxes are still hugely unpopular.

Provinces that rely heavily on developing fossil fuels like Alberta and Saskatchewan ruled out a carbon tax even before the meetings got underway.

The country's two biggest provinces, Ontario and Quebec, have a cap and trade system that punishes companies for growing their carbon footprints. 

But the provinces against the tax are now in the tough position of either deciding on some sort of carbon pricing themselves or having it forced on them the prime minister.

Trudeau did not go as far as saying he would impose the tax, but the understanding is that every province will have at least some model of carbon pricing, and that provinces risk losing the revenue the tax creates if they cede control to the federal government.

Pressure in B.C.

But while Clark is trying to lobby her colleagues, there is pressure mounting at home.

Simon Fraser University sustainable energy professor Mark Jaccard has calculated that for the province to hit its emission targets by 2020, the carbon price will have to more than triple to $100 a tonne.

When former premier Campbell introduced it in 2008, it was supposed to increase over time, but Clark insists the tax is frozen at $30, and there are no plans for an increase.

"Climate policy is very difficult. It is always very difficult," said Jaccard. "That is why we need politicians to show leadership and not be faking it.

We have examples around the world of politicians who acted on climate and got re-elected, in this case it was Gordon Campbell. But you have to be careful. Climate policy always has a very negative benefit-loss ratio."

NDP environment critic George Heyman wants the premier to be more aggressive.

"Emissions have gone up four per cent since Christy Clark became premier," says Heyman. "A recent Environment Canada report to the United Nations framework convention on climate change projects B.C.'s emissions will rise by 2020 by a whopping 32 per cent. What we really need to know is what is the premier going to do to get to legislated carbon reduction targets."

Heyman's comments illustrate the the unsteady middle ground Clark finds herself perched upon.

Not only does she have to advocate on the national stage for a carbon tax, but she also has to fend off foes within the province that are calling for the tax to be increased.