The Number Left Out: Bringing Population into the Climate Conversation

December 16, 2010 • Climate Change & Mitigation, Daily Email Recap

Thanks to Bob Engelman for this article. This article refers to a new Worldwatch Report on the population-women-climate linkage, which can be found at For a Time magazine blog by Krista Mahr about the report, see

The Number Left Out: Bringing Population into the Climate Conversation

Robert Engelman

Numbers swirl around climate change.

So many parts per million of greenhouse gases in the atmosphere. So many gigatons of carbon dioxide emitted. So many degrees Celsius of temperature rise that we hope won’t happen. Yet one number rarely comes into play when experts or negotiators talk about the changing atmosphere and the warming of the planet: the number of humans putting heat-trapping gases into the air.

The relative silence isn’t hard to understand. Population is almost always awkward to talk about. It’s fraught with sensitivity about who has how many children and whether that is anyone else’s business. It’s freighted with sexuality, contraception, abortion, immigration, gender bias, and other buttons too hot to press into conversation. Yet two aspects of population’s connection to climate change cry out for greater attention-and conversation.

One is that population-especially its growth, but other changes as well-matters importantly to the future of climate change, a statement that as far as I can tell is not challenged scientifically. (The Intergovernmental Panel on Climate Change, for example, accepts the accuracy of the so-called Kaya identity, which names population among the four factors that determine emissions growth from decade to decade.) And, two, addressing population in climate-friendly ways is also fundamentally people-friendly, in that it involves no “population control,” but rather the giving up of control-especially control of women’s bodies by people other than themselves.

A new Worldwatch Institute report, which I authored, offers details, findings, and recommendations on both the importance of population in climate change and how to address it. The report looks at some of the history of the population-climate link-in particular, interesting work by William Ruddiman, who hypothesizes that the agricultural revolution contributed to global warming thousands of years ago. And it addresses the common objection that population growth can’t be that important in greenhouse gas emissions growth because countries with high per capita emissions tend to have smaller families than low-emitting countries.

Equity in per capita emissions, I argue, is an essential goal-and without it, no global effort to shrink emissions can succeed. The imperative of an equal sharing of atmospheric carbon space is among the most powerful arguments for a smaller world population. When greenhouse gases other than fossil fuel carbon dioxide-such as methane and “black carbon”-are considered, per capita emissions gaps are not as wide as many writers believe. And the amount of all these gases that equal emitters can contribute without altering the atmosphere shrinks in direct proportion to population’s growth.

Arguments about population’s role in climate change are unnecessarily heated, however. Even if the growth of human numbers played only a minor role in emissions growth, it would be worth discussing-not because addressing population will somehow resolve our climate predicament, but because ultimately no other strategy on its own will either. We need the widest possible range of strategies-economic, political, technological, and behavioral-that are both feasible and consistent with shared human values.

On population, the most effective way to slow growth is to support women’s aspirations. Almost all women aspire to gain an education, to stand in equality with men, and to make decisions for themselves-including whether and when to give birth. Policies and programs to help women achieve these aspirations exist in many places. But they don’t get the attention, support and funding they deserve. And they are rarely seen as climate-change strategies.

As societies, we have the ability to end the ongoing growth of human numbers-soon, and based on human rights and women’s intentions. This makes it easy to speak of women, population, and climate change in a single breath.

Current World Population


Net Growth During Your Visit