Teenage activist Greta Thunberg condemned global leaders at a UN climate change summit Monday for failing to tackle greenhouse gas emissions — repeatedly asking, “How dare you?”

“This is all wrong. I shouldn’t be up here. I should be back in school on the other side of the ocean,” said the visibly emotional 16-year-old Swedish girl, who recently sailed across the Atlantic aboard a zero-carbon sailboat.

“Yet you have come to us young people for hope. How dare you? You have stolen my dreams and my childhood with your empty words,” she added.

Thunberg told the UN that even the strictest emissions cuts being discussed only give the world a 50 percent chance of limiting future warming to 0.72 degrees Fahrenheit from now, which is a global goal.

“We will not let you get away with this,” she thundered in an impassioned speech opening the UN’s Climate Action Summit. “Right now is where we draw the line.”

She continued: “People are suffering, people are dying, entire ecosystem are collapsing. We are in the beginning of a mass extinction and all you can talk about is money and fairy tales of eternal economic growth. How dare you?

“For more than 30 years, the science has been crystal clear. How dare you continue to look away and come here and say you’re doing enough when the politics and solutions needed are still nowhere in sight.

“You say you hear us and that you understand the urgency but no matter how sad and angry I am, I do not want to believe that, because if you really understood the situation and still kept on failing to act, then you would be evil and that I refuse to believe.”

Thunberg ended her remarks with a warning.

“You’re failing us, 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.”

The young activist has become the global face of a growing youth movement against climate inaction that mobilized millions in a worldwide strike on Friday.

UN chief António Guterres called the summit to reinvigorate the faltering Paris agreement, which 66 nations have responded to with promises to achieve carbon neutrality by 2050.

It comes as more emissions are being released into the atmosphere than at any point in history, triggering global weather hazards from heat waves to powerful hurricanes to destructive wildfires and rapidly acidifying oceans.

Thunberg first made headlines when she launched a school strike last year before Sweden’s general election to protest global warming.

Her weekly “Friday for the Future” protests gained traction with other teens, inspiring other student strikes in about 100 cities across the world.

The activist — who has been nominated for a Nobel Peace Prize — has credited being on the autism spectrum with helping her explain climate change in clear terms.

In a surprising turn of events, President Trump made a brief appearance Monday at the summit, which he had been expected to skip.

The president — who has repeatedly expressed doubt about the overwhelming scientific consensus on manmade causes of global warming — listened to remarks by German Chancellor Angela Merkel and Indian Prime Minister Narendra Modi.

Earlier, opening the summit, Guterres said: “The climate emergency is a race we are losing, but it is a race we can win.”

With Post wires