Peter Kalmus, out of his mind, stumbled back toward the car. It was all happening. All the stuff he’d been trying to get others to see, and failing to get others to see — it was all here. The day before, when his family started their Labor Day backpacking trip along the oak-lined dry creek bed in Romero Canyon, in the mountains east of Santa Barbara, the temperature had been 105 degrees. Now it was 110 degrees, and under his backpack, his “large mammalian self,” as Peter called his body, was more than just overheating. He was melting down. Everything felt wrong. His brain felt wrong and the planet felt wrong, and everything that lived on the planet felt wrong, off-kilter, in the wrong place.

Nearing the trailhead, Peter’s mind death-spiralled: What’s next summer going to bring? How hot will it be in 10 years? Yes, the data showed that the temperature would only rise per decade by a few tenths of a degree Celsius. But those tenths would add up and the extreme temperatures would rise even faster, and while Peter’s big mammal body could handle 100 degrees, sort of, 110 drove him crazy. That was just not a friendly climate for a human. 110 degrees was hostile, an alien planet.

Lizards fried, right there on the rocks. Elsewhere, songbirds fell out of the sky. There was more human conflict, just as the researchers promised. Not outright violence, not here, not yet. But Peter’s kids were pissed and his wife was pissed and the salience that he’d so desperately wanted others to feel — “salience” being the term of choice in the climate community for the gut-level understanding that climate change isn’t going to be a problem in the future, it is a crisis now — that salience was here. The full catastrophe was here (both in the planetary and the Zorba the Greek sense: “Wife. Children. House. Everything. The full catastrophe”). To cool down, Peter, a climate scientist who studied coral reefs, had stood in a stream for an hour, like a man might stand at a morgue waiting to identify a loved one’s body, irritated by his powerlessness, massively depressed. He found no thrill in the fact that he’d been right.

Sharon Kunde, Peter’s wife, found no thrill in the situation either, though her body felt fine. It was just hot … OK, very hot. Her husband was decompensating. The trip sucked.

“I was losing it,” Peter later recalled as we sat on their front porch on a far-too-warm November afternoon in Altadena, California, just below the San Gabriel Mountains.

“Yeah,” Sharon said.

“Losing my grip.”

“Yeah.”

“Poor Sharon is the closest person to me, and I share everything with her.”

Sometimes everything is both too much and not enough. George Marshall opened his book, “Don’t Even Think About It: Why Our Brains Are Wired to Ignore Climate Change,” with the parable of Jan Karski, a young Polish resistance fighter who, in 1943, met in person with Supreme Court Justice Felix Frankfurter, who was both a Jew and widely regarded as one of the great minds of his generation. Karski briefed the justice on what he’d seen firsthand: the pillage of the Warsaw Ghetto, the Belzec death camp. Afterward, Frankfurter said, “I do not believe you.”

The Polish ambassador, who had arranged the meeting on the recommendation of President Franklin Roosevelt, interrupted to defend Karski’s account.

“I did not say that he is lying,” Frankfurter explained. “I said that I didn’t believe him. It’s a different thing. My mind, my heart — they are made in such a way that I cannot accept. No no no.”

Sharon, too, possessed a self-protective mind and heart. A high school English teacher and practiced stoic from her Midwestern German Lutheran childhood, she didn’t believe in saying things you were not yet prepared to act upon. “We find it difficult to understand each other on this topic,” Sharon, 46, said of her husband’s climate fixation.

Yet while Sharon was preternaturally contained, Peter was a yard sale, whole self out in the open. At 46, he worked at NASA’s Jet Propulsion Lab, studying which reefs might survive the longest as the oceans warm. He had more twinkle in his eye than one might expect for a man possessed by planetary demise. But he often held his head in his hands like a 50-pound kettlebell. Every time he heard a plane fly overhead, he muttered, “Fossil fuel noise.”

For years, in articles in Yes! magazine, in op-eds in the Los Angeles Times, in his book “Being the Change: Live Well and Spark a Climate Revolution,” on social media, Peter had been pleading, begging for people to pay attention to the global emergency. “Is this my personal hell?” he tweeted this past fall. “That I have to spend my entire life desperately trying to convince everyone NOT TO DESTROY THE FUCKING EARTH?”

His pain was transfixing, a case study in a fundamental climate riddle: How do you confront the truth of climate change when the very act of letting it in risked toppling your sanity? There is too much grief, too much suffering to bear. So we intellectualize. We rationalize. And too often, without even allowing ourselves to know we’re doing it, we turn away. At virtually every level — personal, political, policy, corporate — we repeat this pattern. We fail, or don’t even try, to rise to the challenge. Yes, there are the behemoth forces of power and money reinforcing the status quo. But even those of us who firmly believe we care very often fail to translate that caring into much action. We make polite, perhaps even impassioned conversation. We say smart climate things in the boardroom or classroom or kitchen or on the campaign trail. And then … there’s a gap, a great nothingness and inertia. What happens if a human — or to be precise, a climate scientist, both privileged and cursed to understand the depth of the problem — lets the full catastrophe in?

Once Peter, Sharon and their 12- and 14-year-old sons set their packs down at the car on that infernal Labor Day weekend, they blasted the air conditioning, then stopped for Gatorade and Flamin’ Hot Doritos to try to recover from their trip. But the heat had descended not just on Peter’s big mammal body but on millions of acres of dry cheatgrass and oak chaparral.

That same afternoon, around 1 p.m., the Bobcat fire started five miles from their house in the Los Angeles hills.

Peter’s climate obsession started, as many obsessions do, with the cross-wiring of exuberance and fear. In late 2005, Sharon got pregnant with their first child, and in the throes of joy and panic that accompanied impending fatherhood, Peter attended the weekly physics colloquium at Columbia University, where he was working on an astrophysics Ph.D. The topic that day was the energy imbalance in the planet — how more energy was coming into earth’s atmosphere from the sun than our atmosphere was radiating back out into space. Peter was rapt. He’d grown up a nerdy Catholic Boy Scout in suburban Chicago, and had always been, as his sister Audrey Kalmus said, someone who “jumped into things he believed in with three feet.” He’d met Sharon at Harvard. They’d moved to New York so she could earn a teaching degree. For a while, before returning to school, Peter had made good money on Wall Street writing code. Now here he was hearing, really hearing for the first time, that the planet, his son’s future home, was going to roast. Full stop.

This was a catastrophe — a physical, physics catastrophe, and here he was, a physicist about to have a son. He exited the lecture hall in a daze. “I was kind of like, ‘Are we just going to pretend this is like a normal scientific talk?’” he told me, recalling his thoughts. “We’re talking about the end of life on Earth as we know it.”

For the next eight months, Peter walked around Manhattan, “freaking out in my brain,” he said, like “one of those end-is-near people with the sandwich boards.” He tried converting Columbia’s undergraduate green groups to his cause. Did they care about the environment? Yes. Did they care about the planetary catastrophe? Well, yes, of course they did, but they were going to stick with their project of getting plastic bags out of dining halls, OK? He tried lobbying the university administrators to switch to wind power. Couldn’t even get a meeting. Nothing made sense. Why was Al Gore spending a fortune to make a climate movie only to flinch at the end of “An Inconvenient Truth” and say, essentially, Just buy more efficient light bulbs? Almost nobody saw it — really saw it. WE ARE HAVING AN EMERGENCY. There was only one possible endgame here if humans didn’t stop burning fossil fuels, fast: global chaos, mass violence, miserable deaths.

Peter and Sharon’s friends came over to meet and bless their baby, Braird, shortly after he was born in June 2006. All the guests went around the room offering wishes for the child. When Peter’s turn came, he said he hoped that his son didn’t get shot at in climate-induced barbarity and that he did not starve.

Peter and Sharon rented a house with a big avocado tree when they moved to California, in 2008, for Peter’s dream postdoc studying gravitational waves at Caltech. Braird was 2 and Sharon was nursing newborn Zane. Peter and Sharon had both come from families with four kids, and they didn’t want Braird to be an only child — and having a child when you want one is also immeasurably wonderful, too wonderful, in this case, to give up. (They did later decide to forgo a third.) In Peter’s first run at grassroots activism, he organized a climate protest with a friend. Only two people showed up. Peter joined Transition Pasadena, a community group dedicated to producing “a more resilient city and for living lighter on our Earth.” He also said he tried pushing “to focus the group around global heating and climate breakdown,” but the members, he said, wanted to talk about “gardening and city council meetings,” not the apocalypse, so Peter and Transition Pasadena parted ways.

Four years into climate awakening and action, Peter felt he had accomplished nearly zero. One night, frustrated with inaction and disgusted with fossil fuel use, he sat at his computer and calculated the sources of all his own emissions so he could go about reducing them.

In the morning he presented Sharon with a pie chart.

This was one of those moments that both distorted and crystalized the scale problems inherent in addressing climate change, the personal and the planetary, the insignificant and the enormous, warping and reverberating as if modulated by a wah-wah pedal. Peter himself believed that you can’t fix climate change with individual virtue any more than you can fix systemic racism that way. But he also knew, at some point, “You have to burn your ships on the beach,” as Richard Reiss, a climate educator and fellow at the Institute for Sustainable Cities at Hunter College, put it. You need to commit, perhaps even create drama, and make real changes in your life.

By far the biggest wedge of the pie chart was Peter flying to scientific meetings and conferences. For the family, if Peter quit flying, it meant he’d be home more to help with the kids. Sharon reserved the right to keep flying if she wanted. Win-win.

Peter’s second-largest source of emissions was food. So he started growing artichokes, eggplant, kale and squash, plus tending fruit trees, and that was great. Then he started composting — OK, that’s great, too. He also started keeping bees and raising chickens, and soon raccoons and possums discovered the chickens and Peter began running outside in his underwear in the middle of the night when he heard the chickens scream. Baby chicks lived in the house, which the boys loved. Braird got stung by bees while Sharon was at a meditation retreat and it turned out Braird was allergic and he went into shock.

Next came dumpster diving (which eventually — and thankfully — morphed into an arrangement with Trader Joe’s to pick up their unsellable food every other Sunday night). Peter’s haul — “seven or eight boxes,” according to Sharon; “three boxes,” according to Peter — included dozens of eggs with only one broken. Flats of (mostly not moldy) strawberries. Bread past its sell-by date. Peter did his best to put things away before he fell asleep because waking up to the mess drove Sharon nuts. But … it was a lot. Low-carbon living was a lot.

They stopped using the gas dryer. They stopped shitting in the flush toilet and started practicing “humanure,” composting their own crap. Sharon had lived with an outhouse in Mongolia, “so that was something I was used to,” she said. Plus, to be honest, she liked the local, organic anti-capitalist politics of it. “Marx writes about this in ‘Capital, Volume 1’ that one of the reasons Europeans started to use chemical fertilizers is because people started to move into the cities and off of the land, … and people stopped pooping out in the countryside, so it became less fertile.” The main problem, for Sharon, was that their bathroom was small and the composting toilet was inside. They used eucalyptus leaves to try to cover up the smell, but then little bits of leaves got all over the bathroom, too. After a while Peter moved the composting toilet outdoors. He also built an outdoor shower that Sharon found quite lovely, “rustic and California.”

Sharon commiserated with a friend who was married to a priest. How do you have an equal marriage with a man who’s trying to save the world? The priest’s wife, too, found “it impossible for her to have any space for herself,” Sharon said. “Because he was called by God to minister to people. When she tried to do her own thing, it wasn’t as important as his.” Motherhood was hard enough. Sharon wanted to write a novel. She wanted to write poetry. She wanted to go for a run, or even a walk, in peace. “His dreams were so much more heroic and important that I had to sort of, I don’t know,” she said. “I had to go along with it.”

The most trying component of the low-carbon experiment for Sharon was the 1985 Mercedes that Peter converted to biodiesel. Maeby, as Sharon hate-named the car — as in Maeby we’ll get there, Maeby we won’t — arrived in their lives in 2011, just as Sharon was starting an English Ph.D. at UC Irvine and commuting 50 miles each way. Yes, they took family summer road trips to go camping and visit friends. But on the winter trips to visit their families in the Midwest, the grease coagulated in the cold, which made Maeby break down more. Some nights Sharon cried in the motel room, but “when it’s daytime it all seemed better,” she said. She talked about renting a car or even flying home but never did. Still, late one night on a very cold, dark and lonely Utah highway when Peter was under the broken-down car, and Braird and Zane were in the back seat, screaming, and Sharon was revving the engine at Peter’s request — she started to wonder if she had Stockholm syndrome.

Sometimes, Sharon thought of Peter as being like “John the Baptist, a voice in the wilderness, crying out, ‘Repent, repent!’” This was said with love but also annoyance. As Larissa MacFarquhar explored in her book “Strangers Drowning,” extreme do-gooders often provoke us. We find them ridiculous, self-righteous, sometimes even perverse or narcissistic moralists for whom, MacFarquhar writes, “It is always wartime.” Just figuring out how to raise children on the Earth, right now, presented so many existential questions. Peter often indulged in a half-joking zombie apocalypse mentality. He wanted to teach his boys to grow crops, to defend themselves, to fix things. “I do think we need to be talking about the collapse of civilization and the deaths of billions of people,” he said.

When she was at her gloomiest, Sharon, too, felt scared to leave her sons on this planet, but she also called on her tight-lipped German upbringing to create a bubble of denialist peace. “Things you don’t want to confront, just ignore it. Pretend it’s not there,” she said. Her “ethics of care,” as she called it, involved encouraging the boys to take music lessons, read books and even meditate when she could persuade them to join her. She wanted to prepare her sons to be creative and resilient. If the planet was crumbling, they’d need rich interior lives.

Did Sharon want the boys to worry? “I don’t know, I don’t know,” she said. That was the never-ending, urgent, timeless question. How much do we want our children to understand about the horrors of the world?

In 2012, Peter switched fields, from astrophysics to earth science, because he just couldn’t stop obsessing. This meant backpedaling in his career, quitting the Laser Interferometer Gravitational-Wave Observatory (LIGO) experiment, three founding members of which would go on to win the 2017 Nobel Prize in physics. Still, even his new job was a strange fit. Science itself — with its cultural terror of appearing biased — was a strange fit.

Peter had given up expecting emotional comfort. He’d given up on decorum. He had nightmares about being on planes. “The emissions, you know,” he said. “It feels like the plane is flying on ground-up babies to me.” Even the simplest decisions led him into deep philosophical rifts. The boys’ music lessons, to Peter, seemed woefully, almost willfully anachronistic, a literal fiddling while Rome or Los Angeles burned.

Peter kept trying to figure out ways to make his voice heard. He organized climate cafes, modeled on death cafes, places for people to gather to share grief (Sharon did not attend). He started No Fly Climate Sci, a grassroots group of academic institutions and individual scientists committed to flying less. He kept writing, posting, organizing, talking. This was not always well received. Before the pandemic, Peter stood on the sidelines of Braird’s soccer games when it was 113 degrees. “And I’d be telling the other parents: This is climate change,” he said. “And, you know, they don’t want to hear that during a soccer game. But I can’t not do it. I can’t.”

WE ARE HAVING AN EMERGENCY — Peter thought that all day, every day. “Here I am with a retirement account,” Peter said. Did he need a retirement account? What was the world going to be like in 2060, when he was an old man? He’d been careful with himself not to become a doomer. Doomers, in his mind, were selfish. They’d given up on the greater good and retreated to their own bunkers, leaving the rest of us to burn. Still, despite Peter’s commitment to keep working toward global change, Sharon found Peter’s florid negativity distasteful at times. “There’s almost like a pornographic fascination with ‘Oh, I’m going to imagine just how bad everything is going to be,’” she said.

Sharon staged minor rebellions to maintain a sense of self — little stuff, like using lots of hot water when she did the dishes, and bigger stuff, like she stopped talking sometimes. Braird and Zane, too, each absorbed and reacted to Peter’s passionate cri de coeur in their own ways. Zane, the younger one, started doing his own regular, Greta Thunberg-style climate strikes in front of city hall. Braird, the older, meanwhile, was entering his teens, differentiating and waxing nihilistic. When asked what he wanted to do with his future, Braird said, “What future?” When asked what he thought about climate change, he sunk a dagger into his father’s heart like only a child can. Braird said, “I don’t really think about it.”

On the Tuesday evening after Labor Day, two days after the family returned from their infernal backpacking, Peter, still recovering from heat exhaustion, stood at the sink doing dishes. Braird played League of Legends on his bed. Sharon sat meditating, as she did from 7-8 p.m. each night. Then the emergency alerts blew up their phones. An evacuation warning, the Bobcat fire. The day before, in the ongoing horrible heat, they’d taped their windows shut against the smoke but they hadn’t packed go bags. They never really believed their house would burn. The state was a climate warzone. Military helicopters had rescued 200 people trapped in a Sierra lake by the Creek fire, which had thrown up a plume of flames 50,000 feet. Cal Fire was predicting the Bobcat fire would not be contained for six weeks.

Sharon finished meditating. Then she started photographing all their stuff, including the insides of closets and drawers, because that’s what insurance adjusters tell you to do: Document your property so you can make a stronger claim. Peter snapped. He didn’t care about the pictures or the insurance. He just wanted to let the house incinerate. He felt done pretending that anything was normal, and he decided that now would be a good time to tell Sharon that he’d felt frustrated and gaslit by her all these years.

“WE NEVER EVEN TALK ABOUT CLIMATE CHANGE! DO YOU EVEN CARE ABOUT CLIMATE CHANGE?” he said. This did not go well.

She threw a laundry basket. “YOU HAVE GOT TO BE FUCKING KIDDING ME,” she shouted. “Our entire lives are about climate change.”

There it was, that gap we build around knowing and integrating, to protect our own lives and minds. Yet after the fight, after finally saying aloud what he’d been thinking for almost 15 years, Peter felt better. Not because anything was different. Nothing was different. The situation remained unshakably, cosmically wrong. The only reason to care about insurance, books, paintings, the house, was if you believed that there would be a stable planet on which to enjoy those things in 20 or 40 or 80 years. If you believe there’d be a “planet with seasons, where you can grow food and have water, and you can go outside without dying from heatstroke,” Peter said. “I don’t have that anymore, that sense of stability.”

But he also knew, deep down, that Sharon could not, and should not, give that up. She was a more anxious person than he was. They both knew that. “For me to stay sane, there’s only so much I can take,” Sharon said. Earlier on the night of their big fight they’d watched “The Handmaid’s Tale,” as they did each Tuesday. Sharon often thought about the main character, June. “You have to moderate how you think. You have to think in little chunks, so you can endure, just like June does,” she told me. “You have to make sacrifices so you can survive. If you can survive to fight another day, then maybe the right opportunity will present itself. You can’t kill yourself — well, you can. But that’s not the option I want to take.”

Maeby is now gone. Peter drives an electric car. The composting toilet remains outside, though Peter admits, “The other three family members are not interested in contributing at all.” Peter’s current project is making climate ads. Is this how he can tell the story of what is happening to the world in a way that will make people not just hear and retreat but act? He thinks about this all the time. How do you describe an intolerable problem in a way that listeners — even you, dear reader — will truly let in?

All through October and November, the Bobcat fire continued to burn. It grew to 115,000 acres. Its 300-foot-high flames licked up against Mount Wilson Observatory, where scientists first proved the existence of a universe outside the Milky Way. The fire continued to burn well into December, when UN Secretary-General António Guterres urged, with middling effect, the nations of the world to declare a climate emergency. So far, 38 have done so. The United States is not one of them. In January, a team of 19 climate scientists published a paper, “Underestimating the Challenges of Avoiding a Ghastly Future,” that said, “The scale of the threats to the biosphere and all its life forms — including humanity — is in fact so great that it is difficult to grasp for even well-informed experts.” The language of this sentence could not be more dire. It makes the mind go numb.

So how, with our limited human minds, do we attend enough to make real progress? How do we not flinch and look away? The truth of what is happening shakes the foundations of our sense of self. It asserts a distorting gravity, bending our priorities and warping our whole lives. The overt denialists are easy villains, the monsters who look like monsters. But the rest of us, much of the time, wear pretty green masks over our self-interest and denial, and then go about our days. Then each morning we wake to a new headline like: “The planet is dying faster than we thought.”

While I was trying (and failing) to process it all, Peter called to make sure I understood the importance of a comment he’d made: He’s no longer embarrassed to tell people he would die to keep the planet from overheating. He’s left behind the solace of denial. He’s well aware of the cost. “What a luxury to feel that the ground we walk on and this planet that is rotating around the sun is in some sense OK.”