My darling child,

My hope is that a hundred years from now, we not only have a wonderful climate on our beautiful planet, but also that it will be filled with people like my longtime friend and associate, Melinda Welsh, who inspired and put together the Letters to the Future project. If so, it will be a wonderful place to live.

But we will never meet.

You will be reading this letter 100 years from now. I will have departed this planet long ago.

We will never talk. I will never be able to cradle you in my arms, tell you stories, take you for a walk, spoil you rotten.

You have much of my DNA. You also have my love. I love you now even before you have come into being.

It is because of this love that I was in such despair in November 2015. For my generation continues to pour so much carbon into the air that we are raising the Earth’s temperature. This is changing our weather, raising our ocean levels and bringing environmental destruction to our planet. And to yours.

Many of us actively supported the environmental movement. But, in 2015, it seemed our efforts were no match for the corporate interests that made so much profit from the Earth’s destruction. It did not seem possible to save the planet.

But then something happened: It was the kids.

At a similar moment in history, leaders of the civil rights movement in 1963 were discouraged and up against tremendous odds. But then something happened. Three thousand black junior high and high school students walked out of their schools to march to Birmingham, Ala., to end segregation.

Many of the brave young people in the Children’s Crusade were arrested. Many were blown down the street with high-pressure fire hoses. They were attacked by vicious police dogs. Their courage revitalized the civil rights movement.

And so it happened again. It started with a song. A catchy Earth song created by a Brazilian musician. It went viral.

Then one Friday afternoon at 2 p.m., a Japanese sophomore stood up during math class and sang the Earth song. She is not sure why she did it. She said it just seemed silly to be sitting learning about math when the world was being destroyed.

She was stunned when all of her classmates stood up and joined her singing the Earth song. Someone posted the video online. The following Friday afternoon, in thousands of classrooms, kids stood up and sang the Earth song. And then the following Friday, hundreds of thousands of kids were singing the Earth song. The following Friday it was millions. Then tens of millions.

Then the kids began convincing their parents, their aunts and uncles, their older brothers and sisters to sing the Earth song on Friday afternoons. Suddenly at offices, at hospitals, in prisons, in churches, on subways, on planes, one person would start singing. And then everyone would join in.

On Earth Day, April 22, with a billion people singing, something happened. The people of the world decided to save their planet.

We did it for you. Now please do it for your great-great-grandchildren too.

Your loving great-great-grandfather, Jeff.