Kudos to the Berkeley City Council for addressing the issue of over-population in its declaration of a climate emergency at last week’s Council meeting. This is a distinct breakthrough in the way mainstream thinking – political, economic, and the press – has dealt with the problem of global warming. They’ve been blind to the reality that the principal culprit, CO2 emissions, is a function not only of per capita emissions, but of population, the number of people doing the emitting.

As far as the public is informed, the campaign to reduce world CO2 seems concerned only with the former – driving a hybrid car, having your utility switch from coal to natural gas, putting solar panels on your roof. The role of population is completely ignored. But consider just two examples of how human numbers work to prevent our solving this problem:

In 1950 there were 2.5 billion people in the world and total annual world CO2 emissions were 6 billion metric tons. The world’s population is now 7.6 billion. If average world per capita emissions had just stayed the same, tripling the population would have tripled total emissions. That would have been bad enough!

But the reality is even worse. Total emissions increased six-fold, to 36 billion tons, because large population cohorts – including 1.3 billion Chinese – changed almost overnight from an agrarian lifestyle to an industrialized one. China’s per capita emissions jumped from 1.8 tons in 1999 to 7.6 in 2014, making them the world’s largest total emitter of CO2, 10 billion tons annually.

The question is how much CO2 should the world emit annually, if there’s to be any hope of reversing global warming? Obviously, today’s 36 billion tons is too much – but how much less should it be? A 2009 report in Scientific American concluded, “Global greenhouse gas emissions will need to be at least 50 percent below 1990 levels by 2050.” That would be 12-13 billion tons of CO2 a year.

How many people would it take to produce such a total? That would depend on what percentage of the world’s population has become industrialized, and where the world’s average per capita emissions level stands.

To pose a simple hypothetical: Assume half the world’s population is still agrarian; the other half industrialized. For convenience, use China’s “before” and “after” per capita emission numbers. The world’s agrarians would emit 1.8 tons per capita, the industrialized 7.6. Average world per capita emissions, then, would be 4.7 tons. Dividing that into a hoped-for world total emissions of 12 billion tons gives a world population of only 2.55 billion people.

The formula is inescapable. For total annual CO2 emissions to reach any such goal, we must find some combination of reducing average world per capita emissions, and/or reducing world population.

Professional environmentalists believe we should do both.

A 2009 study from the London School of Economics “recommended that an optimum mix of carbon-reducing methods includes family planning as one of the primary methods.” In 2012, Britain’s Royal Society report on climate change highlighted the importance of both slowing population growth and reducing per capita CO2. The IPCC itself, in 2014, stated, “CO2 emissions could be lower by 30% by 2100 if access to contraception was provided to women expressing a need for it… not only in poor countries, but rich ones like the US, where there’s unmet need for reproductive health services and high CO2 emissions per capita.”

Then why is conventional thinking so resistant to the idea of reducing population?

Probably because of our obsession with economic growth, which too often depends on population growth. No one in the public sphere dares suggest reducing growth. As just one example, in reports for Transportation for America the Northern California “megaregion” estimated its population would grow 50.7% from 2010 to 2050 and Florida predicted its would increase 80.2%. But neither place, nor any of the other nine megaregions reporting, suggested that preventing population growth might be a strategy to pursue. On the contrary, the project’s mission statement speaks of “building capacity for sustainable population and economic growth in the future.”

That premise is irrational. Growth without end-point is unsustainable.

It’s time for professional economists to recognize this and to teach the world how to run a healthy economy with a stable, even smaller, number of people – and free us to add population reduction to the attack on climate change.

George Gitlitz is a retired general surgeon and the father of a UC Berkeley grad.
George Gitlitz is a retired general surgeon and the father of a UC Berkeley grad.