António Guterres is one of TIME’s 2023 Earth Award honorees

My dear great-great-granddaughter,

I wish I could be with you as you open this letter in the year 2100.

My mind is flooded with curiosity about your life, your hopes and dreams, and what kind of world is outside your window.

But I must confess, I am fixed on one question: Will you open this letter in a spirit of happiness and gratitude—or with disappointment and anger at my generation?

As I write you in 2023, humanity is losing the fight of our lives: the battle against climate upheaval that threatens our planet.

If I were with you now, you might ask if we saw disaster coming.

Yes, we did.

We are making a mess of our planet through bottomless greed, timid action, and an addiction to fossil fuels that is driving temperatures to unlivable new highs around the world every year.

Scientists, civil society, the U.N.—and most inspiring of all, young people—have led the charge for climate action. But too many leaders have failed to step up.

Today, our world stands at a crossroads, with two paths before us that will have a direct impact on your future.

The first leads to a future of relentless temperature rise, deadly droughts and famines, melting glaciers, and rising seas. Communities ravaged and erased by floods and wildfires. Extinction and biodiversity loss on an epic scale.

In short, a trail of destruction.

The second path leads to the legacy you deserve: breathable air, better health, sustainable food systems, clean water, and robust, circular economies. A future powered by renewable energy and high-quality green jobs.

I am determined that humanity follows this second path. We have the information we need. We have the tools and technology.

Read more: U.N. Head: Climate Change Can Prove the Value of Collective Action

What we need is the political will to forge a peace pact with nature and transform how we grow food, use land, fuel transport, and power economies.

Wealthy countries must help less-wealthy ones cut carbon emissions and make huge investments in renewable energy and the protection of vulnerable communities.

Of course, even if we take all these actions, our climate will still change in dramatic fashion by the time you are born.

But we can limit the damage, and provide every country and community with ways to adapt and become more resilient.

A future with only 1.5°C (2.7°F) of global warming may not deliver us to climate heaven, but it will save us from climate hell.

So which path did my generation take?

My dear great-great-granddaughter, by the time you open this letter, you will have your answer. You will know whether we succeeded or failed in our fight for your future.

You are decades from birth, but I already hear you. The central question from you and all humanity both haunts and motivates me.

“What did you do to save our planet and our future when you had the chance?”

I will not relent in making sure my generation answers that essential call.

I will stand for climate action; climate justice; and the better, more peaceful, and sustainable world you and all generations deserve.

Guterres is Secretary-General of the U.N.

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