Greenpeace activists scale CN Tower

Greenpeace activists climb CN Tower in Toronto to protest against U.S. and Canada's stand on greenhouse gas emissions

Two Greenpeace activists pulled off a daring stunt Monday by scaling Toronto's CN Tower, in an attempt to draw attention to the issue of climate change.

The activists, Steven Guilbeault, 31, of Montreal and Chris Holden, 23, of England, began climbing the world's tallest free-standing structure at 4 a.m. ET using the tower's steel maintenance cables.

When they reached the observation deck 340 metres up they hung a banner reading "Canada and Bush Climate Killers."

The environmental group is protesting the failure of both Canada and the U.S. to ratify the 1997 Kyoto agreement to cut greenhouse gas emissions.

It's urging Canada to follow Europe's lead in supporting the protocol instead of waiting for the U.S. An international meeting on the issue is under way in Bonn.

Officials later erected scaffolding to help the activists down after pouring rain made their descent difficult. The exhausted pair were one-third of the way down when they were taken inside the building.

Toronto police say Guilbeault and Holden will be charged with trespassing or public mischief.