“I think that would make you the queen of our tribe,” he said. “Especially the Three-Fifty boys. I don’t think they’ve had a proper feed in a couple of weeks.” Roger and Carlos had finished playing Robin Hood without incident, cleared their trash, and sauntered back to the body count. Practically whistling while they worked.

“Why does Pete call them that?”

“It’s their organization. Three-fifty-dot-org.”

“But what does that mean?”

“Parts per million,” he said in a muffled way, between bites. “Honestly, I’m a little worried about those two. They exist on political commitment and gorp.”

She thought: Gorp? But asked, “Parts per million?”

“Three hundred fifty parts per million,” he replied. “The number of carbon molecules the atmosphere can hold, and still maintain the ordinary thermal balance. It’s an important figure. I suppose they want to draw attention.”

Roger came back to retrieve his coat from where he’d left it on the ground, offering a quick little wave. The coat was patched copiously with duct tape. If he gets cold enough, Dellarobia thought, maybe he’ll tape up those bare legs as well. She wondered if she should offer to find him some trousers at Second Time Around.

“It’s a greenhouse gas, carbon,” Ovid added. “It traps the heat of the sun. That number has been going up. Right before our eyes, as they say.”

“You’re telling me somebody counts the atoms?”

“It’s not very difficult. With the right equipment.”

Her heart was still thumping like a drum, as it had all morning whenever she saw or thought of seeing him. But his talk steadied her, and his vulnerability. He had practically swallowed his sandwich whole. She set hers aside and dug in her purse for something presentable in the way of an emergency food supply. “So the carbon goes up, when we burn oil and stuff.” She was working to hold her thoughts in place.

He nodded. “Up, up, up.”

She found what she was looking for, a single-serving cup of diced peaches, and handed it to him. “So what goes out of whack, when it hits three-fifty?”

“The thermal stability of the planet.” He studied the little plastic cup for a moment before grasping and pulling off the foil seal. She watched him down it like a glass of water, and tried to think of any other edibles she might be carrying on her person.

“What are we up to so far?”

He swallowed a few times before speaking. “About three-ninety.”

“What? We went past? Why hasn’t everything blown up?”

He studied the empty cup in his hand. “Some would say it has. Hurricanes reaching a hundred miles inland, wind speeds we’ve never seen. Deserts on fire. In New Mexico we are seeing the inferno. Texas is worse. Australia is unimaginably worse—a lot of the continent is in permanent drought. Farms abandoned forever.”

She pictured orchards like the Cooks’ dying on the other side of the world, for the opposite reason. Rain being sent to the wrong places, in the wrong amounts. “Why wouldn’t they just irrigate the farms?” she asked.

“Because of firestorms.”

“Oh.”

“Walls of flame, Dellarobia. Traversing the land like freight trains, fed by dead trees and desiccated soil. In Victoria hundreds of people burned to death in one month, so many their prime minister called it hell on earth. This has not happened before. There is not an evacuation plan.”

She remembered telling Dovey that hell had gone out of fashion. They sat in silence. Through the trees she saw Carlos stand up from his crouch and do some kind of a yoga pose, folding his arms together over his head to stretch his muscles. They never complained, those two boys. “Is the number still going up?” she asked.

“Everything that has brought us here continues without pause,” Ovid said.

She thought of Cub kicking at the frost. “So will winter just end, then?”

“I suppose it might, but it wouldn’t be our worry anymore. It will only take a few degrees of change, global average, to knock our kind out of the running.”

She stared, her first completely direct look at him since the accidental sighting. “What do you mean, out of the running?”

“Living systems are sensitive to very small changes, Dellarobia. Think of a child’s temperature elevated by two degrees. Would you call it normal?”

“A hundred, that’s low-grade fever,” she said. “Aches and chills.” Dellarobia disliked the thermometer she kept in her makeup drawer, the treacherously slim glass pipe and its regime of wakeful nights, the croups and earaches. Her children’s cheeks hot to the touch, their racked sobs that wrenched her will for living.

“And if the temperature keeps going up?” he asked.

“More? At a hundred and three I’d head for the emergency room. That’s four and a half degrees. More than that, don’t make me think about.”

“Interesting,” he said. “I just read a UN climate report of many hundred pages, and its prognosis for a febrile biosphere matches the one you just gave me in a sentence. Degree for degree.”

She felt very unsettled by the fever talk. Just the smell of rubbing alcohol weakened her knees.

“It keeps me awake nights, that report,” he said, shadowing her thoughts. “A four-degree rise in the world’s average temperature might be unavoidable at this point. So we are headed for the ER, as you put it. The accumulation plays out for a very long time, even if we stop burning carbon.”

“If you stop something, it stops,” she said, sounding a little too fine.

“We used to think so. But there are unstoppable processes. Like the loss of polar ice. White ice reflects the heat of the sun directly back to space. But when it melts, the dark land and water underneath hold on to the heat. The frozen ground melts. And that releases more carbon into the air. These feedback loops keep surprising us.”

How could this be true, she thought, if no one was talking about it? People with influence. Important people made such a big deal over infinitely smaller losses.

“So it’s not a question of having Floridian winters in Tennessee,” he said. “That is not even under discussion.”

“Is there some part of this I can actually see?”

“You don’t believe in things you can’t see?” he asked.