He tilted his head. “Partially, it’s because of shifting weather patterns. And partially it’s because some lunatic decided to pave the Sahara Desert with black rectangles. As if a massive disruption of heat distribution near the Mediterranean Sea wouldn’t have any effects.”

Stratt rolled her eyes. “I knew there’d be weather effects. We just don’t have any other choice.”

He pressed on. “Your abuse of the Sahara aside, we’re seeing bizarre phenomena all over the world. The cyclone season is off by two months. It snowed in Vietnam last week. The jet stream is a convoluted mess changing day by day. Arctic air is being brought to places it’s never been before, and tropical air is going well north and south. It’s a maelstrom.”

“Get back to the three and a half billion dead people,” Stratt said.

“Sure,” he said. “The math of famine is actually pretty easy. Take all the calories the world creates with farming and agriculture per day, and divide by about fifteen hundred. The human population cannot be greater than that number. Not for long, anyway.”

He fiddled with a pen on the table. “I’ve run the best models I have. Crops are going to fail. The global staple crops are wheat, barley, millet, potatoes, soy, and most important: rice. All of them are pretty sensitive about temperature ranges. If your rice paddy freezes over, the rice dies. If your potato farm floods, the potatoes die. And if your wheat farm experiences ten times normal humidity, it gets fungal parasites and dies.”

He looked at Stratt again. “If only we had a stable supply of three-anused mud sloths, maybe we’d survive.”

Stratt pinched her chin. “Nineteen years isn’t enough time. It’ll take thirteen years for the Hail Mary to get to Tau Ceti, and another thirteen for any results or data to come back. We need at least twenty-six years. Twenty-seven would be better.”

He looked at her as if she’d grown another head. “What are you saying? This isn’t some optional outcome. This is happening. And there’s nothing we can do about it.”

“Nonsense,” she said. “Humanity has been accidentally causing global warming for a century. Let’s see what we can do when we really set our minds to it.”

He drew back. “What? Are you kidding?”

“A nice blanket of greenhouse gases would buy us some time, right? It would insulate Earth like a parka and make the energy we are getting last longer. Am I wrong?”

“Wha—” he stammered. “You aren’t wrong, but the scale… and the morality of deliberately causing greenhouse-gas emissions…”

“I don’t care about morality,” Stratt said.

“She really doesn’t,” I said.

“I care about saving humanity. So get me some greenhouse effect. You’re a climatologist. Come up with something to make us last at least twenty-seven years. I’m not willing to lose half of humanity.”

Leclerc gulped.