QUEBEC — Liberal Leader Michael Ignatieff has unveiled a climate-change plan that doesn't include any targets for greenhouse-gas emissions but instead seeks to keep the temperature of Planet Earth in check.

With the start of the UN convention on climate change in Copenhagen just days away, most nations are basing their climate-change plans on meeting emissions targets by a certain date.

The Liberals' wide-ranging proposal, presented Thursday in Quebec City, takes a global approach, aiming to limit the planet's temperature from warming by two degrees Celsius from pre-industrial levels.

It also includes a cap-and-trade system that would reward green businesses and punish polluters, and Ignatieff hopes his plan might eventually be integrated into a continental system with the U.S.

During a news conference after his speech, Ignatieff insisted that keeping world temperatures in check qualifies as a target.

"We've said very clearly there is a scientific target and we must, as a planet, as Canada, in conjunction with our allies make sure that the planet does not heat more than two degrees," Ignatieff told reporters at Universite de Laval.

"And then I've laid out a huge agenda of things that we need to do to hit that target -- it's a target."

Environment Minister Jim Prentice pounced to deride the Liberal plan as an empty shell.

"It has no target in it whatsoever so I don't know how one could call it a plan under any stretch of the imagination," Prentice said in Ottawa following question period.

"Everyone else in the world has been arriving at commitments on targets. That's what Copenhagen is all about."

The Conservative government wasted so little time launching an offensive against Ignatieff's plan that, in fact, they began trying to thwart it right in the middle of the Liberal leader's speech.

At the precise moment that Ignatieff was laying out his vision of a greener Canada, Prime Minister Stephen Harper let it be known that he would attend the upcoming UN convention on climate change in Copenhagen.

Harper had said as recently as Wednesday that he would not attend.

"What a coincidence," Ignatieff told a news conference, shortly after his speech to several hundred people.

"I think it's essential that the prime minister should be there and I'm a little surprised that it took him so long to get there, but he should be there, he must be there."

Ignatieff demanded that Harper do more than simply show up in Copenhagen, urging the prime minister take an active role in the negotiations.

In his speech, he highlighted what a Liberal government would do to reach its target of keeping the planetary thermometer under control.

Ignatieff said the centrepiece of his environmental plan would be a cap-and-trade system -- where companies must buy credits if they pass a certain emissions level while greener companies collect credits for under-polluting.

The policy moved the party farther away from former Liberal leader Stephane Dion's so-called Green Shift proposal -- a plan that included a carbon tax on greenhouse gas emissions -- which flopped with the Canadian public during the 2008 election campaign.

Ignatieff said the cap-and-trade system must be compatible with the U.S. plan to reduce greenhouse gases -- even if no U.S. cap-and-trade system actually exists.

He said he hoped such a plan would fit into a global system, and work in conjunction with any plan set up in the U.S.

But he said that Canada should go ahead and create the system -- and make it equitable across all regions of the country -- even before the Americans have established theirs.

"Provinces are beginning to take action and what I'm saying is let's not wait for the Americans," said Ignatieff, adding that British Columbia, Alberta, Ontario and Quebec are already moving ahead.

"That's the Harper excuse: 'We can't do anything until the Americans act.' "

Ignatieff believes that Canada would generate quick results from the U.S. if it established a cap-and-trade system that would ultimately be compatible with any eventual American system.

"What is more likely to get action on climate change in the United States than if you have a workable model in Canada?" asked Ignatieff, who did not explain how a compatible system could be created in advance.

Ignatieff also said he supports using the stricter baseline year of 1990 -- favoured by most developed countries and the backbone of the international Kyoto accord -- to calculate emissions cuts.

The Harper government prefers using the more lax baseline of 2006.

Ignatieff said his plan would benefit provinces, like Quebec and Manitoba, that have already been working over the last decade and a half to reduce their emissions.

The Liberal leader also laid down a number of other markers in his wide-ranging speech on the environment.

He joked that even the oil industry is ahead of the Harper government on the need for a green economy.

He said he wanted to quadruple the amount of renewable energy used in Canada by 2017 -- Canada's 150th birthday -- and that Ottawa should invest more heavily in solar, wind and geothermal energy.

Ignatieff also said Canada should adopt the toughest vehicle-emissions standards on the continent.

He also wants Canada to be a better steward of the Arctic and the Northwest Passage, and to lay down rules about what other countries can do there.

A spokesman for the environmental group Equiterre praised Ignatieff's plan for recognizing the efforts of provinces and industrial sectors that have already begun reducing their greenhouse-gas emissions.

"The Quebec industrial sector has achieved and surpassed the Kyoto targets," said Steven Guilbeault, who attended the Liberal leader's speech.

"And quite in opposition to what the Conservative speech would have us believe, they didn't do that by closing down shops or laying off people.

"They doubled their production since 1990 while reducing their greenhouse-gas emissions ... I think there is a recognition here today that this can be done in Canada."