Any reality we are given is not set in stone,

it can be changed.

I come from Costa Rica,

a country known for our deep commitment to peace,

our high level of education

and our far-sighted stewardship of nature.

But it wasn't always like that.

Way back in the '40s,

my father, José Figueres Ferrer,

was a young farmer, tilling the soil of these mountains,

and cultivating his vision of a country grounded in social justice

and guided by the rule of law.

His vision was tested, when in 1948,

the government refused to accept the result of democratic elections

and brought in the military.

My father could have been indifferent,

but he chose to do what was necessary to restore democracy,

surviving the burning of his home and his farm.

From here, he launched a revolutionary army

of a few courageous men and women,

who against all odds, defeated the government forces.

Then he disbanded his army,

outlawed the national army,

and redirected the military budget

to establish the basis of the unique country Costa Rica is today.

From my father, I learned stubborn optimism,

the mindset that is necessary to transform the reality we're given

into the reality we want.

Today, at the global level,

we face a rapidly accelerating climate emergency,

daunting because we have procrastinated way too long.

We now have one last chance to truly change our course.

This is the decisive decade in the history of humankind.

That may sound like an exaggeration, but it's not.

If we continue on the current path,

we condemn our children and their descendants

to a world that is increasingly uninhabitable,

with exponentially growing levels of disease,

famine, and conflict,

and irreversible ecosystem failures.

Conversely, if we cut our current greenhouse gas emissions in half

over the next 10 years,

we open the door to an exciting world

where cities are green, the air is clean,

energy and transport are efficient,

jobs in a fair economy are abundant,

and forests, soil and waters are regenerated.

Our world will be safer and healthier,

more stable and more just than what we have now.

This decade is a moment of choice unlike any we have ever lived.

All of us alive right now share that responsibility

and that opportunity.

There are many changes to make over the next 10 years,

and each of us will take different steps along the way.

But all of us start the transformation in one place, our mindset.

Faced with today's facts,

we can be indifferent,

do nothing

and hope the problem goes away.

We can despair and plunge into paralysis,

or we can become stubborn optimists

with a fierce conviction that no matter how difficult,

we must and we can rise to the challenge.

Optimism is not about blindly ignoring the realities that surround us,

that's foolishness.

It's also not a naive faith that everything will take care of itself,

even if we do nothing.

That is irresponsibility.

The optimism I'm speaking of is not the result of an achievement,

it is the necessary input to meeting a challenge.

It is, in fact, the only way to increase our chance of success.

Think of the impact of a positive mindset on a personal goal you have set yourself.

Running a marathon, learning a new language,

creating a new country, like my father,

or like me, reaching a global agreement on climate change.

The Paris Agreement of 2015 is hailed as a historical breakthrough.

What we started in utter gloom

when I assumed leadership

of the international climate change negotiations in 2010,

six months after the failed Copenhagen meetings,

the world was in a very dark place on climate change.

No one believed we would ever agree on global decarbonization.

Not even I believed it was possible.

But then I realized,

a shared vision

and a globally agreed route toward that vision was indispensable.

It took a deliberate change of mindset, first in me,

and then in all other participants,

who gradually but courageously moved from despair to determination,

from confrontation to collaboration,

until we collectively delivered the global agreement.

But we have not moved fast enough.

Many now believe it is impossible

to cut global emissions in half in this decade.

I say, we don't have the right to give up or let up.

Optimism means envisioning our desired future

and then actively pulling it closer.

Optimism opens the field of possibility,

it drives your desire to contribute, to make a difference,

it makes you jump out of bed in the morning

because you feel challenged and hopeful at the same time.

But it isn't going to be easy.

We will stumble along the way.

Many other global urgencies could temper our hope for rapid progress,

and our current geopolitical reality could easily dampen our optimism.

That's where stubbornness comes in.

Our optimism cannot be a sunny day attitude.

It has to be gritty, determined, relentless.

It is a choice we have to make every single day.

Every barrier must be an indication to try a different way.

In radical collaboration with each other,

we can do this.

For years, I had a recurring nightmare

in which I saw seven pairs of children's eyes,

the eyes of seven generations,

staring back at me, asking,

"What did you do?"

Now, we have millions of children in the streets,

asking us adults the same question,

"What are you doing?"

And we have to respond.

Like our fathers and mothers before us,

we are the farmers of the future.

I invite each of you to ask yourself:

What is the future you want,

and what are you doing to make that future a reality?

You will each have a different answer,

but you can all start by joining the growing family

of stubborn optimists around the world.

Welcome to the family.