Should you not have kids because of climate change? It’s complicated.

When Meera Sanghani-Jorgensen was in her 30s, she and her husband began to discuss having children. They both wanted to have kids, but Sanghani-Jorgensen couldn’t shake the feeling that, by giving birth, she might be doing something bad for the earth.

“I wanted to have a child, but I was also looking at the planet and thinking: ‘Well, what kind of future will we have if there’s more of the same?’ ” she said. She thought about the diapers, the party favors, the toys, and the billions of tons of...