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Want to Slow Climate Change? Stop Having Babies

Carbon dioxide doesn’t kill climates; people do. And the world would be better off with fewer of them.

That’s a glib summary of a serious and seriously provocative book by Travis Rieder, a moral philosophy professor and bioethicist at Johns Hopkins University.

When economists write about climate change, they’ll often bring up something called the Kaya identity—basically a multiplication problem (not an espionage novel) that helps economists estimate how much carbon dioxide may be heading into the atmosphere. The Kaya identity says the pace of climate pollution is more or less the product four things:

  • How carbon-heavy fuels are
  • How much energy the economy needs to produce GDP
  • GDP per capita
  • Population

After years of policymakers’ yammering about carbon-light or carbon-free this-or-that, Rieder basically zeroes in on the fact nobody wants to acknowledge: The number of people in the world—particularly in affluent countries—is literally a part of the equation.

Think of Rieder’s as the argument waiting in the wings should the 195-nation Paris Agreement, which came within a shade of enactment this week, fail to address the problem.

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