Climate change is now unequivocally an emergency according to the latest report from the IPCC. Our only hope lies in extremely rapid abandonment of fossil fuels and reversal of forest loss. But these lifeline scenarios also assume birth rates plummet in high-fertility regions. Jane O’Sullivan offers a reality check.
By Jane O’Sullivan
The Intergovernmental Panel on Climate Change (IPCC) recently released the first part of its Sixth Assessment Report (AR6-WG1). United Nations Secretary General António Guterres called it a “code red for humanity.” Climate change has already degraded many of our planetary support systems and the urgency of decarbonising human activities is beyond dispute. All of the IPCC’s scenarios see global temperature rise exceeding 1.5oC by 2040. If heating continues, planetary systems will cross “tipping points” which might escalate the heating uncontrollably: “hell on earth” according to an Oxford climatologist.
But hope is proffered that, if we halve emissions by 2030 and decarbonise completely by 2050, then global heating could be halted and eventually reversed. The report explores five scenarios, with our ray of hope dependent on the two with the lowest emissions.
The modelling for these scenarios uses the “shared socioeconomic pathways” (SSPs) that were developed in 2013 for use in AR5. The scenarios allow climate modellers to incorporate a wide range of socioeconomic variables in a consistent and relatively transparent way. But they have the problem of bundling different components, such as low global cooperation and high population growth, so that the effects of these factors can’t be explored individually.
In AR6, our lifeline scenarios are SSP1-1.9 and SSP1-2.6. These are both built on the SSP1 settings, and both reduce emissions rapidly, one achieving a radiative forcing of 1.9 W m–2 in the year 2100, and the other 2.6. These forcings correspond to roughly 1.5oC and 2oC global heating, respectively (Figure 1).
The problem is, SSP1 assumes a pathway for global population that is very far from the one we’re on. Achieving something approximating it is conceivable, but it would require strong and explicit efforts to get birth rates down rapidly in all high-fertility countries. According to most projections, virtually all the population growth this century will be accounted for in Africa (elsewhere, modest growth in some countries will be off-set by modest shrinkage in others). SSP1 anticipates Africa would fall below two children per woman around 2042, and end the century averaging 1.3 children per woman (Figure 2). Such rapid fertility decrease is highly unlikely with current levels of inattention to the issue. Can we expect diverse and dispute-ridden Africa to emulate South Korea’s rapid demographic transition, when that country had a single, stable government, a high-profile national family planning program and a secular, culturally homogeneous population?
Most unrealistically, SSP1 assumes that this rapid transformation has been happening for a decade already, positing a fertility rate of 3.2 for Africa in 2020, where the latest data put it at 4.3 (and that might be optimistic, given that the impacts of the pandemic on family planning access and child marriage are yet to be measured).
Even the “middle of the road” SSP2 scenario anticipates much lower population growth than does the United Nations. For Africa, SSP2 is similar to the UN’s low projection, which the UN considers unrealistic. (It is merely illustrative of the impact of having half-a-child fewer births per woman than the medium projection in all countries). Only SSP3 lies within the UN’s range of probable population outcomes. Climate modellers have found it impossible to contain global heating to less than 2oC using SSP3. This is at least partly due to the expanded agricultural area needed to feed more people.
So, the IPCC report’s most hopeful global scenarios assume rapid fertility decreases in Africa and other high-fertility regions that are not happening and that would take much greater efforts to achieve. But the IPCC’s climate change commentary contains nothing at all to encourage greater investment and attention to extending family planning in under-served regions. It contains nothing to inform people in developed countries that having fewer children is a powerful way to reduce future emissions. We are left to assume, as the SSP scenarios do, that improvements in development and education, by themselves, will drive the rapid birth reductions needed.
That is a serious mistake. Where birth rates have fallen rapidly, they were invariably due to family planning efforts. While improved education and incomes can help reduce fertility, such improvements are rarely possible to sustain while population growth remains high. By allowing infrastructure and services to get ahead of the growing needs of the people, lower birth rates enable poverty reduction and better access to education more strongly than the reverse.
Let’s not exaggerate the implications. Changes to birth rates take time to affect the number of people present in a big way. Between now and 2050, when decarbonisation needs to happen, the contribution of any feasibly lower population pathway would be relatively small, perhaps 10%. (The ship has already sailed on earlier estimates that put it at 16%.) But the importance of population cumulates over time. The ability of nations to feed themselves, preserve their remaining biodiversity and live sustainably after 2050 will depend crucially on overall human numbers, the fewer the better. What we do about population in this decade might make the difference between having 12 billion or 7 billion people to sustain in 2100.
More immediately, their rate of population growth will have a very large impact on whether poor countries will have the resources to achieve “clean development”, to invest in education and to reverse deforestation. It not only affects how many people are exposed to climate disasters, but how well equipped they will be to cope with them. For them, population growth itself is a greater threat to the sufficiency of infrastructure and government stability, and a far greater threat to food, water and energy security, than is climate change.
The SSPs are right to link population outcomes with economic development, but assume causation in the wrong direction. They consequently neglect the important initiatives needed to reduce birth rates fast enough. This can be done with voluntary measures that empower women and families to achieve their goals, but it will not be done by pretending population growth is going to fix itself. If people’s future security depends on most of them choosing small families, they have a right to be told this. UN charters assert that people have a right to choose their family size freely and responsibly, but they can’t choose responsibly if the consequences of population growth are hidden from them, or are actively denied.
Nigeria’s former President Olusegun Obasanjo loses sleep over how to keep Nigerians fed and “how to keep the keg of gunpowder of the large army of unemployed youth from exploding.” But many current leaders dream on that youthful, growing populations are a boon. The IPCC is not providing the wake-up call they need.