Three days after the biggest climate strike in history, the United Nations hosted its first-ever Climate Action Summit.

The meeting, organized by UN Secretary-General António Guterres, was meant to rally member nations to enact stricter emissions standards to slow the effects of climate change.

The star of the show was the 16-year-old Greta Thunberg, who sailed to New York City for the event from Sweden on a zero-emissions sailboat.

Thunberg has emerged as the face of youth climate activism around the world over the past year. On Monday, Thunberg kicked off the UN summit with two of her youth colleagues, giving an impassioned and emotional speech to the UN General Assembly.

"This is all wrong. I shouldn't be standing here. I should be back in school on the other side of the ocean," she said with tears in her eyes. "Yet you all come to me for hope? How dare you. You have stolen my dreams and my childhood with your empty words."

For four minutes, Thunberg held the room in thrall as she chastised leaders for talking about "money and fairy tales of eternal economic growth" while people suffer.

"People are dying. Entire ecosystems are collapsing," Thunberg said.

Thunberg's youth movement

Thunberg launched the "Fridays for Future" movement - or School Strike for Climate (as it says in Swedish on her sign) - in 2018, encouraging students to skip school to demand action on climate change from their governments.

In November, when she was a ninth grader, Thunberg staged a strike for two weeks outside the Swedish parliament, demanding that the government cut emissions by 15% a year.

Now she spends every Friday on strike. On September 20, she was joined in protest by an estimated 4 million people across 161 countries.

climate strike new york greta thunberg

Foto: Thunberg will make her voice heard again on Saturday at the UN Youth Climate Summit in New York City, then speak at the UN Climate Action Summit on Monday.sourceREUTERS/Shannon Stapleton

Thunberg's climate activism garnered her a nomination for the Nobel Peace Prize earlier this year.

Read more: How 16-year-old Greta Thunberg became the face of climate-change activism

"You are failing us," she told world leaders in her speech at the UN summit. "But the young people are starting to understand your betrayal. The eyes of all future generations are upon you. And if you choose to fail us, I say we will never forgive you."

'Change is coming, whether you like it or not'

The UN secretary-general hopes to use the summit to encourage UN member countries to agree to stricter standards regulating greenhouse-gas emissions, using the Paris climate agreement as a benchmark. In December 2015, world leaders pledged that their countries would act to prevent global temperatures from rising by more than 1.5 degrees Celsius (2.7 degrees Fahrenheit), with a 2-degree rise as the absolute maximum.

According to Thunberg, achieving those goals has never been more difficult.

"For more than 30 years, the science has been crystal clear. How dare you continue to look away and come here saying that you are doing enough, when the politics and solutions needed are still nowhere in sight," she said.

Greta Thunberg

Foto: Teenage climate activist Greta Thunberg.sourceAnders Hellberg

The 16-year-old made it clear that she and young people around the world would continue to hold their governments accountable.

"We will not let you get away with this. Right here, right now, is where we draw the line. The world is waking up. And change is coming, whether you like it or not," she said.