We really should call these gatherings of federal and provincial leaders "last ministers' meetings," because no matter how much goodwill, and how many pledges to co-operate are heard going in, the bonhomie never really lasts.

Justin Trudeau is the latest prime minister to learn that shared visions and common goals only go so far when it comes to his fellow first ministers.

The expectation heading into this week's gathering in Vancouver was that Trudeau would emerge with two things: the framework of a national climate change strategy; and a commitment that, over the next six months, all the provinces and territories would work with Ottawa to draft detailed plans that would make Canada a leader in the global effort to address climate change.

In fact, CBC News obtained a draft communiqué written for the leaders back on Feb. 24 that set out the broad areas of agreement.

It promised Ottawa would set up working groups with the provinces and territories in four areas: clean technology and innovation; mitigation opportunities; adaptation and climate resilience; and, most notably, carbon pricing.

It's that last one that gave the prime minister a bit of gas.

Ontario Premier Kathleen Wynne, centre, and Manitoba Premier Greg Selinger, right, listen to Prime Minister Justin Trudeau during the first ministers meeting in Vancouver on Thursday. (Jonathan Hayward/Canadian Press)

"The working group on carbon pricing will provide options on the role of a pan-Canadian approach to carbon pricing in meeting Canada's emission targets," the February draft read, "including different design options taking into consideration existing and planned provincial and territorial systems."

The problem with those marching orders was that a price, in some form, appeared to be a done deal. Non-negotiable. A fait accompli.

Some media outlets had reported before the meeting began that Ottawa wanted a price of $15 a tonne as either a starting point, or a floor. Both suggestions were denied.

Price on carbon?

Still, Saskatchewan Premier Brad Wall objected loudly to any federally mandated price on carbon, arguing it would take money out of his oil-producing province. And he wasn't alone.

Premier Stephen McNeil of Nova Scotia worried that such a mechanism would increase hydro costs in his province where, thanks to the move away from coal, emissions are already on a solid downward track.

The downside is the province now has very high hydro rates, and McNeil argued a carbon tax would just add to that cost for Nova Scotians.

Enter the ubiquitous unnamed federal official, who told CBC News that Trudeau wouldn't wait forever for everyone to get behind carbon pricing, arguing it was a key promise in the Liberals' election platform.

"We feel that we've got a mandate to do it. And we want to do it in co-operation with the provinces," the official said. "But at the end of the day we are going to do it."

A mandate from voters is, of course, a necessary and good thing. It's especially good for pounding your political opponents in your home arena.

But a mandate in a federal election is just that. A mandate from voters in provincial elections is quite a different thing. And Wall isn't about to go to the polls in Saskatchewan this spring having agreed to impose a price on carbon just because Trudeau told him to.

Common ground

So, cue the compromise that emerged Thursday after the leaders broke for lunch.

The final declaration referred to working on "carbon pricing mechanisms adapted to each province's and territory's specific circumstances."

The prime minister was asked, several times, what that actually means. Would it, asked one scribe, still lead to that pan-Canadian price on carbon the Liberals repeatedly promised during the 2015 election campaign?

"Putting a price on carbon is an important part of the suite of tools we have to bring forward to create the low-carbon economy we need," Trudeau told reporters.

"We have an agreement to move forward today in a way that respects jurisdictions across the country."

OK, but is a carbon pricing mechanism the same thing as a price? the questions to Trudeau continued.

"The agreement is that the transition to a low carbon economy will happen by a broad suite of measures that will include a price on carbon."

That's not quite the way Wall sees it.

"If there is a notion that comes forward that this is some sort of licence to pursue a national carbon tax, I'll be in disagreement with that, because that's not my understanding," the Saskatchewan premier said.

So. A misunderstanding perhaps. Or an understanding that the first ministers don't all agree on whether a national carbon price will emerge over the next four months in the shared goal of reducing Canada's emissions.

Will there be new emissions targets? We don't know yet.

Will it include a price on carbon in every province and territory? We'll find out when the prime minister convenes another meeting of first ministers, or perhaps we should call it the next instalment of a last ministers meeting on climate change.

Trudeau, centre, poses with Canada's premiers following the first ministers meeting in Vancouver. (Jonathan Hayward/Canadian Press)