MONTREAL — The Clown hats and witty T-shirt slogans of festive Earth Day marches were a thin veil Sunday for the gloom hanging over environmentalists as they await the launch of a made-in-Canada global warming plan.

With Prime Minister Stephen Harper's government poised to set its own course to cut greenhouse gas emissions, thousands marched in Montreal with smaller crowds gathering across the country to demand the Conservatives honour the targets of the Kyoto treaty.

Under a blazing sun, Shannahn McInnis pushed a stroller with her two-year old daughter who sported a green T-shirt that said, "I run on natural gas.''

McInnis saw the massive Montreal event as a chance to put some pressure on the Harper government.

"I'm extremely pessimistic on it doing anything, but I thought I'd come anyway,'' McInnis said.

"I don't think it's at all a priority to any of the parties except the Green Party and the NDP, and they're so far away from being elected. If that's the case, it wouldn't seem to be a priority for the public, either because they're not electing the parties that consider this the priority.''

Sparse crowds in other parts of the country seemed to emphasize the point.

About 300 mostly youthful activists basked in the spring sunshine on Parliament Hill in Ottawa where they tossed balls and Frisbees while lending an ear to political speeches.

Green Party Leader Elizabeth May predicted the Tory effort will be little more than a public relations ploy designed to camouflage the issue in advance of a federal election.

"The Harper government understands the threat of climate change as an electoral threat,'' May said in an interview just before her speech. "They do not understand it as a threat to the lives of our children and grandchildren.''

The Conservative government was notable by its absence at the events, but Environment Minister John Baird chose another forum to deliver his message.

Baird defended the Tory decision to abandon emission targets in the Kyoto Protocol in an interview on CTV's Question Period. He insisted the government has a better idea.

"The choice is not between Kyoto, strictly adhered to, and doing nothing,'' said Baird.

"We'll come forward with a tough approach, a balanced approach.''

Liberal Leader Stephane Dion made his own CTV appearance to pitch for a Liberal proposal to charge industry a $20-per-tonne carbon levy that would go into an environmental fund and be repaid if companies cut their emission levels.

Dion has been careful to call the levy a deposit rather than a tax -- a term that raises hackles in the Alberta oil patch.

Bloc Quebecois Leader Gilles Duceppe joined the Montreal crowd where he condemned Harper for protecting Alberta oil interests over the health of the Quebec environment.

"Canada is getting rich off oil and Quebec is paying for it,'' Duceppe said.

After taking a shower Sunday morning with water heated by solar power, NDP Leader Jack Layton -- along with wife and fellow MP Olivia Chow -- rode their bicycles on a sunny afternoon to join an estimated 250 people in the Toronto parade.

The threat of smog, combined with rising temperatures, is an immediate threat in Canada's biggest city, where smog and extreme heat alerts have been routine events in recent years.

Paul Mero brought along his children, aged 8 and 6, saying he wants to instill the value of the environment in them.

Mero noted he can insulate his home and replace inefficient light bulbs, but "the government needs to do the bigger things, put the infrastructure in place to encourage people to do these things.''  

At the Montreal rally, McInnis said she's noticed the many little ways governments discourage people from putting the environment first, since her family decided to go without a car.

The price of using Montreal's subway system has steadily rose while she discovered how inaccessible the subway is. Each trip she must drag her stroller and 15-kilogram baby up and down dozens of stairs.

"It's disgusting,'' she said. "It's bad with a stroller, imagine if you're elderly or in a wheelchair.

"When you make environmentalism a priority in your life, that's when you begin to see how the government puts up barriers.''