On Monday, 16-year-old activist Greta Thunberg stood up in front of the world's leaders at the U.N. climate summit in New York City and condemned their inaction in an emotional speech.

"You have stolen my dreams and my childhood with your empty words," Thunberg said. "People are suffering. People are dying. Entire ecosystems are collapsing."

The message of Thunberg and other young climate activists around the world is "crystal clear," says Lisa Helps, mayor of Victoria, who is also at the climate summit.

"They're not mincing words. We have lived irresponsibly, as [Thunberg] says. We've known the science for 30 years and yet still," Helps said.

Teen activist Greta Thunberg assails world leaders for inaction on climate change 1:47

Her visit to New York comes after hundreds of thousands of youth in cities across the world marched in a climate strike on Friday, demanding politicians take immediate action to combat climate change.

It's a movement that Helps said has kept her motivated as she pushes climate strategies in her city.

"The youth voice is important. And it's not just enough to applaud them in the news media or on Twitter, but we actually need to lend our support and our resources to their movement," she said.

"What I'm saying to youth climate activists here in New York, as well as in the city of Victoria and around the province, [is] watch what comes out of the summit because there will be some commitments," Helps said.

"Watch us carefully and hold us accountable."

For her part, Helps said she was asked to represent Victoria as a speaker on two panels about science and cities, and what cities are doing to respond to climate emergencies.

Other panellists included scientists, governors and other city officials from around the world. Discussion focused on what different levels of government can do to work together on climate change and how people can change their behaviour to reduce their impact on the environment, Helps said.

"Victoria is a small powerhouse city and it's starting to catch a little bit of attention in an international arena for the kinds of climate mitigation and resilience strategies that we're undertaking," she said.

Planting pledge

According to the U.N., 70 per cent of global carbon emissions come from cities. Helps said it was apparent at the summit that cities like Victoria are prepared to help national governments meet emissions reduction targets under the Paris Agreement.

Victoria recently promised to plant 5,000 trees on public and private land by the end of next year as part of a challenge from the U.N.

Helps said Victoria was the first Canadian city to make the pledge. The city's urban forest plan also recommends 26 actions to improve the management of trees on public land over the next 50 years.

Helps said climate change offers a "massive" opportunity for cities to build sustainable and resilient communities that benefit the economy and its citizens.

"As we electrify our public transport system, there's obviously a cost savings by not having to put diesel fuel into buses, but there's also a co-benefit like a reduction in particulate matter, a reduction in noise," she said.