Two climate change protesters interrupted Justin Trudeau's speech in Montreal Friday evening when they stepped out of the crowd behind him. The Liberal leader let them ask him a question.

As demonstrator Julianna Duholke unveiled a sign that said "Votons pour le climat" or "Vote for the climate," Trudeau said "excellent question" and approached them with his microphone.

The protesters asked Trudeau what his emissions reduction target would be for the United Nations Conference on Climate Change in Paris in December if a Liberal government were to be elected. Trudeau praised the pair's passion and talked about the importance of the issue, but didn't provide a number.

"I am committed to showing up with all premiers to take on the target we need which is to prevent the two degrees of warming that scientists across the world are looking at as catastrophic," he said.

"We need to step up. We need to work and respect with the provinces that are already putting prices on carbon, we need to make sure we are creating economic growth in a way that protects future generations and that's what we're going to do. Thank you very much." ​

The audience applauded Trudeau's response, his speech ended and the two protesters walked off stage.

The encounter mirrored a similar incident last November, in which Trudeau asked a group demonstrating against the Energy East pipeline to "take a moment to explain" their position.

Deholke and fellow protester Sam Quigley told CBC News after the exchange they were glad Trudeau answered — but weren't satisfied with his response.

They said his failure to provide a specific number as a reductions target is troubling.

Earlier this week, a lone protester unveiled a climate change sign at a rally for Conservative Leader Stephen Harper and was escorted out.