Greta Thunberg's speech at Youth4Climate hits hard at 'empty words and promises'

For a moment, Greta Thunberg sounded like a different activist than the one the world was used to seeing.

"Climate change is not only a threat. It is, above all, an opportunity to create a healthier, cleaner and greener planet which will benefit all of us," the Swedish climate activist said with a bright smile while speaking at the opening session of Youth4Climate event in Milan, Italy, on Tuesday.

Audience members clapped cautiously as Thunberg's face lit up while speaking about "green jobs" and a "smooth transition" to a clean economy. But her tone darkened midway through her speech: "There is no Planet B. There is no Planet Blah. Blah, blah, blah... Build back better. Blah, blah, blah."

Thunberg's uncharacteristically corporate-sounding lines, it turned out, were meant to show the emptiness behind politicians and business leaders' slogans when they speak about climate change.

"Thirty years of blah, blah, blah," Thunberg said acerbically. "Net zero by 2025. By 2050! This is all we hear from our leaders. Words that sound great, but so far have led to no action. Our hopes and dreams drowned in their empty words and promises. Over 50 per cent of all our CO2 emissions have occurred since 1990, and a third since 2005."

Thunberg slammed global leaders for not backing their slogans and speeches with concrete action, and said tackling climate change would not be as simple as creating new green jobs, but that the deeper social roots of environmental destruction had to be addressed.

"Climate crisis is only the symptom of a much larger crisis... of inequality that dates back to colonialism and beyond. A crisis based on the idea that some people are worth more than others, and therefore have the right to exploit and steal other people's lands and resources. It is very naive to believe we can solve this crisis without confronting the roots of it," she continued.

She said the time to let politicians decide what is "politically possible" has long passed, and suggested a popular movement is needed to force governments to make the drastic changes needed to avert catastrophic impacts of a warming climate.

"We can no longer let the people in power decide what hope is," she said. "Hope is not passive. Hope is not blah, blah, blah. Hope is telling the truth. Hope is taking action. Hope always comes from the people. We want real climate action and we want climate justice."

Watch the full speech below.