Another piece in Justin Trudeau’s pursuit of a more engaged and aggressive Canadian stance on international climate policy fell into place Thursday, but many more remain a mystery.

The prime minister announced he’s invited provincial and territorial leaders to Ottawa to discuss Canada’s climate change plans later this month before an international climate conference begins in Paris.

Trudeau had previously invited the provincial and territorial leaders to join him at COP21, the UN-sponsored summit that begins Nov. 30 in the French capital, where the international community hopes to complete a framework for post-2020 climate action.

Trudeau will meet the premiers Nov. 23, just before departing on an extended trip that will take him to London for an audience with the Queen, then on to Malta for a Commonwealth leaders’ meeting before wrapping up with other international leaders at the Paris climate talks.

The Liberal plan has always been to present a united Canadian climate policy to the world, something that has regularly eluded prime ministers going back to Jean Chretien in the 1990s. With provinces holding many of the policy levers on environmental action — and having very different agendas depending on their resource base — getting everyone pulling in the same direction has proved challenging.

“We are having a climate briefing by top scientists for the first ministers and for my own cabinet, to be followed by a working dinner with the premiers to exactly discuss the kind of strong and cohesive message we will be delivering as Canadians in Paris at the very important COP21 conference,” Trudeau said Thursday at his second briefing of the parliamentary media in as many weeks.

The offices of Alberta Premier Rachel Notley, B.C.’s Christy Clark, Ontario’s Kathleen Wynne and Quebec Premier Philippe Couillard immediately confirmed their attendance at the Nov. 23 meeting to The Canadian Press.

Many, many questions remain to be resolved.

– Will the Liberals set a national floor price on carbon and, if so, what will it be and how would it be enforced?

– Will the Liberals endorse another pipeline project now that their favoured option, the Keystone XL pipeline to the U.S., has been killed by presidential order?

– How soon will the Liberals begin to phase out fossil fuel subsidies, as promised in their election platform “over the medium term.”

– What will be the level of Canada’s collective ambition in cutting future greenhouse gas emissions?

Part of the COP21 process includes countries submitting intended targets for emissions cuts, something the Conservatives did last May when they committed Canada to a 30 per cent cut below 2005 levels by 2030.

However the Harper government did not provide a policy blueprint, just as it failed to put Canada on track to meet its previous 2020 target set at Copenhagen and just as the Chretien Liberals failed to produce policies that would achieve the 1997 Kyoto protocol targets.

Trudeau’s new government has refused to set a target for cutting GHGs in advance of Paris, but Environment Minister Catherine McKenna did say the existing Conservative-set mark should be considered the floor.

Environmental groups have also been hounding the Liberals on pipeline policy, asserting any new pipeline capacity will boost Alberta oil sands production and undercut credible Canadian action on emissions.

And a new report Thursday from a Washington-based environmental advocacy group further fanned the policy flames.

The study by Oil Change International asserts that global fossil fuel subsidies amount to US $452 billion annually, of which $78 billion comes as direct government spending and tax breaks. Canada’s subsidies, according to the report, averaged $3.6 billion in Canadian dollars over 2013 and 2014, including just over $2 billion a year from the federal government.

“It is tantamount to G20 governments allowing fossil fuel producers to undermine national climate commitments, while paying them for the privilege,” says the report.

Talk about tax treatment of oil and gas development, combined with pipeline policy, makes federal-provincial unanimity on climate policy devilishly difficult.

On Thursday it was Treasury Board President Scott Brison who was left trying to thread the needle connecting resource extraction and climate action.

“We’re all active as a government, and we will be considering what is the case in terms of what subsidies or approaches …” said Brison when asked about the fossil fuel subsidy phase-out.

“But it’s clear our energy sector is an important sector and developing our energy — getting it to market in a way that is environmentally and economically sustainable — is absolutely key to our government’s agenda.”