The world has yet to apprehend the tectonic shift that will occur as China’s population starts to decline. That long-anticipated event did not occur in 2020, according to official data, but it will probably occur soon. From a climate perspective, the population decline is good news, since fewer people means lower emissions. As with many of the uncertainties surrounding the planet’s future, it’s hard to foresee the exact carbon impact from population decline.
China’s population has been aging rapidly, and policy makers there had hoped that ending the one-child policy in 2016 would encourage more births. The country’s birthrate, however, has not risen and remains well below the level required to increase the population — probably because the one-child rule lasted so long as to create a new norm, and because income in the country has been rising. In 2020, the pandemic may have also depressed fertility rates.
Low fertility rates inevitably will cause China’s population to fall. In 2017, China’s State Council projected that the country’s population would peak in 2030. Last year, the Chinese Academy of Social Sciences released a study projecting that the decline would instead start in 2027. News reports supposedly based on Chinese census data suggested the population had already begun to fall in 2020. The Chinese government asserted those reports were false, and the official data do show a very small increase, from 1.40 billion in 2019 to 1.41 billion last year. But it is clear to most observers that the Chinese population will start to shrink soon, if it hasn’t already.
This matters to the climate because China is the world’s most populous country, and more people mean more emissions and bigger populations at risk from climate change. As a recent paper in the Proceedings of the National Academy of Sciences put it, “The size of the human population, in the near-term and distant future, is a key determinant of climate policy: All else equal, a larger population entails more emissions and therefore more mitigation to achieve a given climate target, and it also means more future people will be vulnerable to climate-related impacts.”
How big is this connection? The effect of population on carbon emissions without any policy or technological changes is not exactly fixed per person, because so many details matter, including the age mix and consumption patterns. But roughly, fewer people mean proportionately lower emissions. Consider comparisons of “shared socio-economic pathways,” estimates that are used internationally to assess future populations. The low SSP1 projection shows a global population of 8.5 billion by 2050, whereas the baseline SSP2 projection for that year is 9.2 billion, for a difference of about 8%. Carbon-equivalent emissions are similarly projected to be roughly 5% to 10% lower in 2050 under the SSP1 scenario compared with the SSP2 baseline. It’s notable that the effects of population choices are often assessed to be materially larger than other plausible changes that can be made to mitigate climate change.
Three caveats to this silver lining are worth noting. First, climate projections already assume that China’s population will shrink; the point here is that the decline seems to be happening more quickly than most official projections had indicated.
Second, as highlighted in a Vox article last year, is the “all else equal” condition. The impact of slower or faster population change depends on whether other actions are taken to protect the climate. Consider, for example, a scenario in which a country adopts binding emissions caps, and requires a tradeable permit for each unit of emissions. More people in that country might put upward pressure on the price of the permits, but would not affect the overall level of emissions, because that would remain constrained by the caps. Less extreme examples show a similar phenomenon: Population and climate mitigation effects interact with one another, making the effect of population alone harder to assess. Nonetheless, in most scenarios, fewer people do mean lower emissions.
Finally, massive technological innovation will be needed to alter the course of climate emissions. Under existing technologies, and unless we are willing to pay sometimes implausibly high green premiums to reduce emissions, many everyday activities — not only air travel but also steel production and container shipping — will continue to produce significant greenhouse-gas emissions. Innovation will thus be essential to a better climate future. But with fewer people, as the Economist and others have emphasized, we may have fewer good ideas about how to innovate. So fewer people is not necessarily the clear climate boon it is often presented to be.
Addressing climate change may require us to wade into potentially awkward topics, including nuclear power and geo-engineering. And while the effect of demographics may not be at the top of the agenda for the Glasgow climate conference later this year, the hard truth is that China’s imminent and sooner-than-expected population decline carries climate benefits.
Peter R. Orszag is a Bloomberg Opinion columnist. He is the chief executive officer of financial advisory at Lazard. He was director of the Office of Management and Budget from 2009 to 2010, and director of the Congressional Budget Office from 2007 to 2008.