At the 2019 annual gathering of world leaders at the United Nations, a 16-year-old climate activist took the mantle of global leadership usually reserved for the US president.

Donald Trump’s decision to not participate in the UN climate summit illustrated just how devastatingly Trump’s climate-denying policies have undermined America’s role in the world as a force for good, and how his actions could contribute to the destruction of the futures of countless billions. Meanwhile, Greta Thunberg called him – and other world leaders – out for their malign neglect in failing to address the single most existential threat humanity faces, while revealing the energy with which a new generation of leaders is determined to act.

If world leaders choose to fail us, my generation will never forgive them | Greta Thunberg Read more

Each year, leaders come to New York and remind us of the promise of the United Nations – the notion that the international community can work together to solve shared challenges. The meetings can also showcase the ability of US leadership to encourage countries to tackle serious threats. These gatherings can yield genuine results – commitments to tackle a pandemic like Ebola, for instance. Whether crafting solutions to pressing challenges or inspiring the world to act, UN general assembly can remind us how much America can achieve when it leads and works together with partners.

Not this year. Of course, Trump’s mere presence is more than enough to sap the power of American diplomacy on the world’s greatest diplomatic stage, and this year Trump again came ready to embarrass himself – and America – by roaming the halls of the UN reminding the public that he attempted to force the president of Ukraine into investigating Joe Biden in a move that should be worthy of a unanimous impeachment conviction.

And so, Trump refusing to participate in the UN climate summit was little surprise from a president who gutted domestic environmental protections, announced his intention to withdraw the US from the Paris climate agreement, and is even trying to prevent California from enacting higher emissions standards for automobiles.

Enter Thunberg. The climate activist from Sweden – who has helped spark a global movement of young people striking from school to press their leaders to urgently confront climate change – was the star of the show. Her remarks reminded us what leadership, courage and sacrifice look like.

Speaking to the assembled world leaders, Thunberg outlined the stakes of inaction on the climate crisis and denounced the world’s focus on “money and fairytales of eternal economic growth”. Thunberg made clear what’s coming: “You are failing us. But the young people are starting to understand your betrayal … We will not let you get away with this … The world is waking up. And change is coming, whether you like it or not.”

Read all of what Thunberg said. Watch the passion – and the justified anger – in how she said it. Too many of the world’s leaders – political, corporate, civic – are collectively robbing the world’s youth of their futures. The lack of action means that young people like her have to sacrifice, Thunberg said: “This is all wrong. I shouldn’t be standing here. I should be back in school on the other side of the ocean. Yet you all come to me for hope? How dare you! You have stolen my dreams and my childhood with your empty words.”

Thunberg’s sacrifice couldn’t find a stronger contrast than the selfishness of Trump, who only looks out for himself. His egotism was illustrated yet again when he mocked Thunberg’s speech.

If politicians can’t find a way to act quickly and on a scale the likes of which the world has never seen in order to mitigate the effects of climate change, the student strikes and marches will pale in comparison to what we are likely to see in the future. If entire generations know as a scientific fact that earth will, in their lifetimes, become violently inhospitable to vast swathes of humanity, what kinds of actions would we expect them to take?

Thunberg is right – change is coming. There are leaders of countries and businesses making commitments to tackle the climate crisis. Local governments, like California, are trying to move ahead on their own when their countries abdicate their responsibility. And, as Thunberg exemplifies, younger generations are beginning to mobilize. One poll of US teenagers noted that roughly one in four people ages 13 to 17 have taken action – attended a protest, taken part in a walkout, written to an public official – to advocate for change in climate policy.

But time is not on our side, and the longer that the actions of Trump and other leaders defending the use of fossil fuels are allowed to stand, the more catastrophic the results will be for our children.

Tackling the climate crisis requires American leadership. America is by far the largest cumulative contributor of emissions since the industrial revolution and is currently the second largest emitter (after China). America has a responsibility to act; the worst effects of climate change cannot be averted without US action, and Americans are already feeling the pain of the climate crisis.

Furthermore, American leadership, when wielded the right way, can produce results. The US has the unique ability to bring countries together on climate, as we saw when the US and China (the world’s largest current emitter) struck a deal that created the political momentum that led to the Paris agreement.

The speech that Thunberg gave should be echoed by an American president and accompanied by sweeping actions to cut emissions. Unfortunately, right now, such an America lies dormant. In his annual UN speech, Trump yet again trumpeted his nationalist “America first” policies that do nothing but spurn the world. Trump has, for the time being, eviscerated the power of American leadership to do good.

But Thunberg and her generation are ready to lead and to sacrifice. The world’s youth won’t accept failure – they have no choice.