If I’ve succeeded as a parent, I’ve now dragged you on backpacking trips into the mountains and bone-chilling paddles across San Francisco Bay. You’ll know what it’s like to sweat and strain across some patch of desolate wilderness, then find yourself somewhere as sacred as any place on Earth. You’ll know just how miraculous it is we’re living amid such immeasurable beauty, one of (at least) 8 million other species on the planet.

And if you’re reading this in 2050, as intended, then you’ll also know how much we’ve messed up. All the unprecedented things in my lifetime — the fires, floods and droughts — will have become commonplace in yours. Our neighbors’ homes will begin flooding at high tides. The Sierra’s deep snows, once merely marking the start of winter, will be a novelty if they arrive at all. The summers, my childhood refuge, will be an assault of heat and humidity more extreme than anything I’ve experienced.

We can’t plead ignorance. Scientists laid it out for us decades ago (1856, really). Our best guess was that averting the worst of global warming would have meant investing 1 to 2 percent of global GDP. A pittance relative to what you’re paying today.

We could not fight for a pristine world, but we could fight for yours. What did we do? Each day, your mom and I tried to live lighter on the planet. There was joy in the effort. At home, we electrified almost everything and changed what we ate. We composted your diapers. We tried to change the communities and the systems around us. Each year, we set aside more of what we earned to support other people in this project. My work, of course, was my legacy to you too;each column was an exploration and love letter to a world I’d like to see.

All this may seem small in isolation. Compared to the problem, it was. Only it wasn’t that simple. As part of writing my column each week, I dug into the social science of how change happens.

Most people will tell you only top-down change matters: grand policies, political victories and technological revolutions. Those are critically important. But the motivation for these often begins with people like you and me — rough tinder that feeds cultural and political change.

From where I stand, hope is not a delusion. Human nature being what it is, we’ll keep making terrible choices. We’ve lost much and stand to lose more.

But one of the things you learn studying ecology is that the natural world, given a chance, is astonishingly resilient. People, too. I’ve watched our nation make strides to thrive alongside the natural world — witnessed humpback whales breach in San Francisco Bay and heard the dawn chorus of the Everglades. I’ve also seen the country turn away. But turning away from climate change won’t be possible, not for long.

You don’t stop fighting because you feel like you’re losing. That’s probably the story of every fight worth having. Know that your mom and dad fought for every chance to give you and your generation a better world.

I love you — the most. Big kisses,

Papa