"Respect Mother Earth": Around 500,000 protesters marched in Montreal rally.

Teen activist Greta Thunberg urged Canadian Prime Minister Justin Trudeau and other world leaders Friday to do more for the environment as she led half a million protesters in Montreal as part of a global wave of "climate strikes."

The 16-year-old Swede met privately with Trudeau but later told a news conference with local indigenous leaders that he was "not doing enough" to curb greenhouse gases responsible for global warming.

"My message to all the politicians around the world is the same. Just listen and act on the current best available science," she said.

Thunberg generated headlines around the world earlier this week with her viral so-called "How Dare You?" speech at the UN climate summit, accusing world leaders of betraying her generation.

"You have stolen my dreams and my childhood with your empty words," she thundered, visibly angry and close to tears.

The teen has inspired millions of youngsters, drawn to her cause by her passion and a mature, committed rhetorical style -- articulated in near-perfect English -- that belies her young age.

"It's incredible to be united in such a way for a common cause," she told the cheering Montreal crowd, adding: "If the people in power won't take their responsibility, then we will."

"This week, world leaders from all around the world gathered in New York. They disappointed us once again with their empty words and insufficient plans," she went on.

"It should not be up to us, but somebody needs to do it. This is an emergency, and we will not be bystanders. We are the change and change is coming."

Trudeau and other Canadian party leaders took a breather from a tight election campaign to join Thunberg at the Montreal rally -- along with around 500,000 protesters, according to organizers.

Walking with his wife and children, Trudeau mingled with a boisterous crowd that brandished placards reading "Respect Mother Earth" and "Make America Greta Again" -- a riff on a campaign slogan popularized by US president and noted climate skeptic Donald Trump.

Two billion trees

One man was tackled by security when he appeared to lunge at the prime minister, while 13-year-old Annabelle Vellend broke out in tears when she spotted Thunberg marching, telling AFP: "I really believe in Greta's movement."

"She is doing amazing things and it's great that she's able to press politicians to act on climate change, during an election," she said.

In his first term, Trudeau cast himself as a champion in the fight against global warming, but his green image was tarnished by his nationalization of an oil pipeline to salvage the construction project after years of delay.

The prime minister said after meeting Thunberg and pledging to fund the planting of two billion trees: "I agree with her entirely. We need to do more."

Earlier this week, the Liberal leader promised Canada would reach net-zero carbon dioxide emissions by 2050, joining 66 other countries that have already signed onto the pledge.

Last Friday, more than six million youths -- and adults -- rallied in "climate strikes" around the world.

Turnout at events a week on was smaller, but still vocal. In Italy hundreds of thousands of young people took to the streets while an estimated 40,000 protested outside New Zealand's parliament, and in Switzerland police intervened when protestors tried to block a major thoroughfare.

"Don't take away my planet, you jerks!" yelled demonstrators who surged through the streets of Madrid singing raucously along to a brass band, and dancing.

Record CO2 emissions

Climate is "being talked about every day, everywhere, by everyone," commented Maria Paralejo, 22.

Her friend Alicia Portela told AFP it wasn't just up to politicians to act. "We have to stop using so much plastic, cut back on eating meat and reuse clothes instead of buying new ones."

Back at the giant Montreal march made up mostly of children and a few adults, Alexanne Lessard stood out in her tree costume.

"I'm here for our future, to show our government that we the majority want to do something and that they can take big steps that will have an impact," she said.

The world's top scientists believe the long-term average temperature rise must be limited to 1.5 degrees Celsius over pre-industrial levels to prevent runaway warming and catastrophic longer term damage.

But the level of emissions being released into the atmosphere has risen to an all-time high, triggering global weather hazards from heat waves to intense hurricanes and raging wildfires.

The UN estimates that the world needs to increase its current efforts five-fold to contain climate change.

The UN summit in New York sought to reinvigorate the faltering Paris agreement on climate change.