Eugenia Kalnay has an interesting talk on a core problem that most people avoid when talking about climate: the growth in human population. It’s a difficult subject politically, because any analysis of the link between emissions growth and population growth invites the simple-minded response that de-population is the solution, which then quickly sinks into accusations that environmentalists are misanthropes.

In her talk, “Population and Climate Change: A Proposal“, Kalnay makes some excellent observations, for example that per dollar spent, family planning reduces four times as much carbon over the next 40-years as adoption of low-carbon technologies, and yet family planning is still not discussed at the COP meetings, because it is taboo. The cause and effect is a little complicated too. While it’s clear that more people means more fossil fuel emissions, it’s also the case that fossil fuels enabled the massive population growth – without fossil fuels the human population would be much smaller.

Kalnay then points out that, rather than thinking about coercive approaches to population control, there’s a fundamental human rights issue here: most women would prefer not to have lots of kids (especially not the averages of 6 or more in the developing world), but they simply have no choice. Kalnay cites a UN poll that shows “in many countries more than 80% of married women of reproductive age with 2 children, do not want to have more children”, and that estimates show that 40% of pregnancies worldwide are unwanted. And the most effective strategies to address this are education, access to birth control, and equal (economic) opportunities for women.

There’s also the risk of population collapse. Kalnay discussed the Club of Rome analysis that first alerted the world to the possibility of overshoot and collapse, and which was roundly dismissed by economists as absurd. But despite a whole lot of denialism, the models are still valid, and correspond well with what actually happened, and that rather than approaching the carrying capacity of the earth asymptotically, we have overshot. These dynamics models now show population collapse on most scenarios, rather than a slight overshoot and oscillation.

Kalnay concludes with a strong argument that we need to start including population dynamics into climate modelling, to help understand how different population growth scenarios impact emissions, and also to explore, from a scientific point of view, what the limits to growth really look like when we include earth system dynamics and resource depletion. And, importantly, she points out that you can’t do this by just modeling human population at the global level; we will need regional models to capture the different dynamics in different regions of the globe, as both the growth/decline rates, and the per capita emissions rates vary widely in different countries/regions.

2 Comments

  1. From post: > “It’s a difficult subject politically, because any analysis of the link between emissions growth and population growth invites the simple-minded response that de-population is the solution, which then quickly sinks into accusations that environmentalists are misanthropes.”

    I would say, it is difficult thing to ask of another, because in many violent places in the world, high fertility and demography are the surest (or only) ways of continuing a way of life.

    > “…the most effective strategies to address this are education, access to birth control, and equal (economic) opportunities for women.”

    I would add humane and equitable government, which protects from a tyranny of the majority.

  2. There is a whole modelling community, the IAM community, who build models which link climate to emissions, and human factors such as economics (& I hope, population). There is a methodology for linking these communities via Representation Concentration Pathways (RCPs), see http://www.iiasa.ac.at/Research/ENE/IAMC/rcp.html

    … which is all to say that I totally agree on the need to understand the impact of population on climate and vice-versa, but I think the option of separating the communities so that we have the physically based models separate from the socially based models, so the differing assumptions and uncertainties can be well understood … is a good one.

    So I vote for *not* modelling population in our climate models, but working on understanding how the physical system and the social systems interact.

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