Al Gore brought his critically acclaimed environmental slide-show to Toronto and Montreal on Wednesday, promoting his Oscar-nominated documentary "An Inconvenient Truth."

In Canada's largest city, tickets for the event were in such high demand that even scalpers got in on the action.

On Craig's List, a website that posts community classified ads, the cheapest pair of tickets was selling for $250.

"I couldn't sell my mother for a ticket," student Vanessa Iafolla joked. "There's just nothing out there.

Tickets went on sale Feb. 7 but sold out quickly, at $20 a piece. Only 1,500 seats were available at the University of Toronto's Convocation Hall, and 500 seats were pre-reserved.

The Toronto Star reported that about 23,000 hopefuls tried to buy tickets online, causing the site to crash.

One online seller named Vicky explained to why she wanted to sell her tickets.

"I really did buy the tickets with the intention of attending the lecture," she said. "But once I discovered just how coveted the tickets were, it got me thinking about whether or not I really need to see Al Gore to be inspired by his message and to be passionate about environmental activism."

Before the show began, she had received offers of $100 to $150 per ticket, but hoped for $200.

Canada's own famous environmentalist, David Suzuki, said Gore deserves honours for his work explaining the dangers of global warming.

"He's become a real crusader," said Suzuki. "I think it's fabulous. I hope he wins an Oscar."

From Gore the bore to we want more

The buzz around 'An Inconvenient Truth' has turned the former U.S. vice-president, once targeted for being too dull, into an unexpected pop icon and leader in the fight against climate change.

"He's definitely got the star power," Ingrid Stefanovic, director of the U of T's Centre for Environment, which is hosting tonight's event, told the Star.

Gore's journey has been a long one as he started creating his slide show in the late 1980s -- building on a interest he developed in college.

"I don't like the phrase 'midlife crisis,''' he told Entertainment Weekly in an interview last year. ''But, yes, I was reevaluating my priorities.''

Fueled by an increasing public awareness on the issue, the show grew from humble beginnings in 2001 to a global phenomenon that has grossed more than $40 million worldwide.

"Never before has all of civilization been threatened," Gore said in Madrid earlier this month, where he was attending a climate change conference. "We have everything we need to save it, with the possible exception of political will. But political will is a renewable resource."

"An Inconvenient Truth" has two Oscar nominations -- for best documentary feature and best original song. Also, Gore has been nominated for a Nobel Peace Prize for his work on raising awareness about global warming.

With a report by CTV's Lisa LaFlamme