O’Neill,B.C., MacKellar,F.L. and Lutz,W. (2001) Population and Climate Change. Cambridge: Cambridge University Press. 266pp.
This essay continues my series of monthly posts in which I select one ‘climate’ book to highlight and review from one of the 44 years of my professional career in climate research (starting with 1984, my first year of academic employment). The series will end in September 2027, the month in which I shall retire. See here for more information about the rational for this series, and the criteria I have used in selecting my highlighted books.
This ‘2001 essay’ can be download as a pdf.
For those following the unfolding politics of climate change during the 1990s, there was no shortage of large international conferences where climate matters were debated: the Second World Climate Conference in Geneva in 1990, the United Nations Earth Summit at Rio de Janeiro in 1992 and, starting in Berlin in 1995, the annual cycle of Conference of Parties to the Convention. But in 1994, there was another mega international UN conference which attracted around 20,000 delegates from various national governments, UN agencies, NGOs, and the media—but where climate change was barely mentioned. This was the International Conference on Population and Development (ICPD), held in Cairo, Egypt, between 5th and 13th September. The Cairo ICPD followed two earlier international population conferences held in 1974 (in Bucharest) and 1984 (in Mexico City), and all three addressed some of the concerns raised by the rapidly growing world population. Over this 20-year period, population had grown by 42 per cent, up from 4 billion in 1974 to 5.7 billion in 1994.
The Cairo Conference discussed issues such as immigration, infant mortality, birth control, family planning, the education of women, and protection for women from unsafe abortion services. The need to slow population growth in developing countries was noted, but the political emphasis of the resulting Cairo Action Plan was on “holistic approaches to reproductive health” and on enhancing women’s rights. The Conference was characterised by disputes about the ethics of China’s ‘one-child’ policy, about the religious implications of promoting contraception and/or abortion, and about the coercive nature of some family planning proposals. There was very little talk about the relationship between population and environment; even less between population and climate change. And there was no recognition that policies to control population growth might actually also function as climate change mitigation policies. One consequence of this fractious Cairo meeting was that population policies slipped quietly down the international agenda; investment by developed countries in international family planning programmes by 2004 had fallen to just thirteen per cent of the target set by the 1994 Conference.
It is against this background that I have selected as my 2001 Climate Book of the Year, ‘Population and Climate Change’, the first major book to directly address the relationship between population and climate change. The book was authored by three academics—Brian O’Neill, Landis MacKellar, and Wolfgang Lutz—all of whom had close links with the International Institute for Applied Systems Analysis (IIASA), located just outside Vienna in Austria. O’Neill had completed his PhD dissertation a few years earlier at New York University, which had examined the atmospheric timescales of greenhouse gases and included a chapter on the role of population growth in future emissions of greenhouse gases. After his PhD, O’Neill went on to complete a post-doctoral fellowship at IIASA, before returning, aged 36, to the USA to take up an assistant research professor position at Brown University, Rhode Island.
The origin of ‘Population and Climate Change’ lay in the four-volume study ‘Human Choice and Climate Change’, published Battelle Pacific Northwest Laboratories in 1998.[1] MacKellar, who was running the Social Security Reform Project at IIASA, was the convening author responsible for that study’s chapter on population, health, and nutrition, for which he enrolled population expert, Lutz, and greenhouse gas scenarios expert, O’Neill, plus other contributing authors. They then realised that a dedicated book was needed to synthesize the current state of knowledge in climate change, population studies, and related fields; it was this that became ‘Population and Climate Change’, with O’Neill as the convening author. The book’s connections with IIASA were signalled by the Institute’s Director, Gordon MacDonald, writing the Forward, where he claimed this was “the first book to take a dispassionate, scientific look at how population affects climate change and society’s ability to adapt to it” [p.vii].
But why did the relationship between population growth and policies and concerns about climate change arouse strong passions, such that a “dispassionate” account was necessary? One reason can be traced back to the earlier provocation made by two young American ecologists, Paul and Ann Ehrlich, in their controversial 1968 book, ‘The Population Bomb: Population Control or Race to Oblivion?’[2] The Ehrlichs offered a bleak Malthusian view of the future if population growth was not checked, forcibly if necessary, and although their follow-on analysis in ‘Population, Resources, Environment’[3] was more measured, the hare had been set running. The co-dependency of population, consumption, technology and the state of the environment was given further illumination in 1972 by the Club of Rome’s ‘Limits to Growth Report’.
The specific question about population growth and climate change came to a head in the early 1990s. Simply put, was climate change caused by too many people having too many children, or by the excessive consumption of those who already had so much? Or, as the Bangladeshi development economist Atiq Rahman posed it in his eponymous edited book from 1993: consumption versus population – which is the climate time bomb?[4] At the time, the Indian development analysts Anil Agarwal and Sunita Narain had a very clear answer to this question. In their scathing riposte to the 1990 World Resources Institute (WRI) report ‘A Guide to the Global Environment’, they accused the North of “environmental colonialism”, pulling no punches about where the blame for global warming truly lay:
The North, with only 20 per cent of the earth’s population, accounts for 85 per cent of the global consumption of non-renewable energy. The North has already used much of the planet’s ecological capital. It will have to take important measures to adjust its pattern of production and consumption in order to mitigate the clear threat to the earth’s environment … to accommodate the industrialisation and economic development of the South.[5]
As well as the Washington-based WRI, Agarwal and Narain also had as their target politicians such as Al Gore who, well before the ICPD in Cairo, was arguing in favour of policies to control population growth: “No goal is more crucial to healing the global environment than stabilising human population.”[6]
It was in the context of this highly charged debate that ‘Population and Climate Change’ was published in 2001. O’Neill and colleagues were of course fully aware of this back story. They acknowledged Rahman’s challenge to the “potent myth that assigns undue importance to population as a factor in climate change” [p.197]. But they were also critical of bodies such as the UN’s Intergovernmental Panel on Climate Change (IPCC) which, following the ICPD in 1994, had shied away from any overt engagement with population policies in their assessment reports. “The IPCC”, say the authors, “paid little attention to population … [its] reports on [climate change] mitigation and adaptation options evaluate a wide range of strategies, but do not consider policies to slow population growth” [p.183].
In ‘Population and Climate Change’, O’Neill and colleagues wanted to rectify this deficiency by systematically and quantitatively evaluating the effectiveness of population policies for climate change mitigation and adaptation. The book combines state-of-the-art analysis of demographic trends and projections—drawing upon Lutz’s demography programme at IIASA[7]—with state-of-the-art modelling of future greenhouse gas emissions, building on O’Neill’s PhD dissertation and the work recently informing the IPCC’s Special Report on Emissions Scenarios, published in 2000.
The authors adopt the Ehrlich-Holden heuristic IPAT formulation—Impact = Population x Affluence x Technology—to perform a sensitivity analysis of greenhouse gas emissions to different assumptions about future world development. “Our central conclusion”, write O’Neill and colleagues, is that while “policies to encourage more rapid demographic transition are likely to significantly reduce greenhouse gas emissions in the long-run” [p.139], in the short-to-medium term it is the consumption and technology factors that dominate. What the IPAT formulation fails to reveal, however, is the sensitivity of future emissions to population age distribution and household structure; it also says nothing about the economics or politics of different policies that might bring about a reduction in fertility.
These conclusions align with O’Neill’s own views which he had published the previous year in a short commentary on the Cairo agenda and climate change,[8]
Reductions in per capita emissions must be the principle route to emission reductions over the next several decades, and must play a central role in long-term emission reductions as well. Nonetheless, slower population growth would make the climate problem easier to solve, and capturing these long-term benefits requires investments in population policies in the immediate future. [p.95].
This conclusion—that policy-makers concerned about climate change should engage directly with population policies—aligned with other work being undertaken for different reasons. For example, Nancy Birdsall’s work at the Centre for Global Development, a think-tank in Washington DC, had shown that “increased spending on population programs is likely to be part of any optimal carbon reduction strategy” [p.203].
One of the book’s reviewers at the time, economist Axel Michaelowa, writing for the journal Climate Policy, observed that “the overall conclusion of the book is sound: ‘no-regret’ population policies … should be pursued, but will have effects on greenhouse gas emissions only with long lags.”[9] Michaelowa’s review also drew out another aspect of the book’s analysis, which is especially pertinent today with early industrialising nations now witnessing falling fertility rates. “A declining population may have problems to adapt [to climate change]”, wrote Michaelowa, “[since] it will come under intense fiscal pressure due to aging. Thus, industrialised countries may revert to pronatalist policies, especially if they do not accept [im]migration as a substitute for births.” It was for this reason that O’Neill and colleagues were sceptical that deliberate and significant reduction of population in industrial countries would be a viable contribution to climate mitigation.
‘Population and Climate Change’ was an important book when it was published in 2001, since it offered the first systematic and quantitative analysis on the relationship between demography and climate change. Michael Dalton, reviewing the book for the journal Climatic Change, praised its “superb scholarship” and readability, considering it essential reading for “anybody seriously interested in global policy”.[10] Partha Dasgupta, an economist at Cambridge University, viewed it similarly recommending it as “the starting point for anyone who wishes to understand and work on this most important of problem areas”. O’Neill and his colleagues were willing to investigate the question of whether, and with what effect, population policies could be considered climate policies, at a time when few others were willing to do so. It laid the path for others to follow, although surprisingly few did.
Nearly a quarter of a century later, it is perhaps moot whether ‘population policies’ have proved to be an effective means of mitigating climate change. It is hard to tell. In the 24 years since 2001, another 2 billion people have been added to the world’s population, which now stands at 8.2 billion. This is a lot of additional people, and a lot of additional emissions. And yet global population growth rates have been steadily falling, down from 1.35 per cent per annum in 2001 to 0.85 per cent today (although this falling trend commenced in the late 1980s, partly linked to China’s one-child policy).
And yet the reticence of international bodies such as the IPCC to engage with the question remains in place. Writing much later in 2018, O’Neill, with colleague John Bongaarts, observed that much of the climate community, “is largely silent about the potential for population policy to reduce risks from global warming”.[11] The conclusions O’Neill, MacKellar and Lutz reached in 2001 about the benefits of population policies for climate change mitigation and adaptation, and about the co-benefits of these policies for human well-being and the wider set of sustainable development goals, remain seemingly underappreciated.
© Mike Hulme, July 2025
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Other significant books published in 2001
Davis,M. (2001) Late Victorian Holocausts: El Niño Famines and the Making of the Third World. London: Verso Books.
As I have reviewed in earlier posts—for example, Micky Glantz’s 1996 ‘Currents of Change’—the 1990s saw a significant expansion of historical and scientific knowledge of past El Niño climatic events in the Pacific Ocean. One person who was following this story, was the late Mike Davis (1946-2022), a historian and self-defined ‘Marxist-Environmentalist’ at the University of California, Irvine. Early in 2001, he published Late Victorian Holocausts: El Niño Famines and the Making of the Third World with Verso Books, a leading radical publishing house, befitting Davis’ ideological bent. A couple of years earlier he had published ‘Ecology of Fear: Los Angeles and the Imagination of Disaster’, which had investigated the relationship between natural disasters and social injustices in Southern California.
Now, in the preface to ‘Late Victorian Holocausts’, Davis refers to the “rekindling” of his ancient interest in climate history, prompted by listening to climate scientists discussing state-of-the-art research on climate oscillations, “a truly exhilarating experience”. From this prompt, Davis develops a powerful narrative relating El Niño events in the latter decades of the nineteenth century to climate change, capitalism, imperialism, and regional famines. His focus is on the El Niño-related famines of 1876–78, 1896–1897, and 1899–1902, and his geographical reach takes him to India, China, Brazil, Ethiopia, Korea, Vietnam, the Philippines and New Caledonia.
With its focus on the impact of colonialism and capitalism on the severity of these climate-induced famines, ‘Late Victorian Holocausts’ was a trailblazer for later authors who sought to re-position climate change as a crisis caused by colonial-capitalism. Davis writes the environment into history rather than inserts history into the environment; as he explains, “There is an extraordinary amount of hitherto unnoticed environmental instability in modern history” [p.279]. The book has been extraordinarily well-cited—over 3,300 citations in 24 years according to Google scholar—and in 2002 won the World History Association Book Prize.
Victor,D.G. (2001) The Collapse of the Kyoto Protocol and the Struggle to Slow Global Warming.Princeton, NJ: Princeton University Press. 178pp.
In March 2001, shortly after taking office, President George W Bush announced that the USA would not be ratifying the Kyoto Protocol, negotiated just over three years earlier during Bill Clinton’s Presidency. The Protocol eventually came into force under international law in 2005, when the Russian Duma and the Canadian Parliament finally ratified it, but it staggered forward until it’s final demise in 2012. Bush argued that the deal would damage the United States’ economy, lead to higher energy prices for consumers, and invite other countries to take advantage of an agreement with little enforcement capabilities.
Several months before Bush’s announcement, the political scientist David Victor was finishing the manuscript for his book, The Collapse of the Kyoto Protocol and the Struggle to Slow Global Warming, which would appear later in 2001. Victor was then a Senior Fellow for science and technology at the Council on Foreign Relations in New York and his training in political science enabled him not just to predict that the Protocol would collapse, but also to identify why. This was a bold intervention at a time early in the new Millennium when most climate analysts, commentators and advocates were placing their hopes that this first international climate treaty would begin the process of bringing greenhouse gas emissions under control. Victor explained that the fundamental flaws of the Protocol arose from “a regulatory system improvidently based on setting targets and timetables for controlling emissions of greenhouse gases” [p.ix]. And he was scathing about the simplistic way in which this policy architecture had been naively transferred across from the 1987 Montreal Protocol which had been designed to limit CFC emissions.
The Protocol’s unhappy decade was about to begin, yet it took me until 2007 to publicly acknowledge the futility of the Protocol’s architecture. By the decade’s end, many others were joining the chorus of lament Victor had started in 2001. Victor had believed from early on that the Protocol’s failure was inevitable and was brave enough to lay out his reasoning in book length form, well before the Protocol’s eventual demise.
[1] Rayner,S. and Malone,E.L. (eds.) (1998) Human Choice and Climate Change. Four Volumes. Columbus, OH: Battelle Press. 1728pp.
[2] Ehrlich,P.R. and Ehrlich,A.H. (1968) The Population Bomb: Population Control or Race to Oblivion? San Francisco: Sierra Books. 201pp.
[3] Ehrlich,P.R. and Ehrlich,A.H. (1970) Population, Resources, Environment: Issues in Human Ecology. New York: WH Freeman & Co. Ltd.
[4] Rahman,A., Robins,N. and Roncerel,A. (eds.) (1998) Consumption Versus Population: Which is the Climate Time Bomb? Dhaka, Bangladesh: The University Press. 123pp. [This book was originally published in 1993 by Castle Cary Press Ltd.].
[5] p.16 in: Agarwal,A. and Narain,S. (1991) Global Warming in an Unequal World: A Case of Environmental Colonialism. Delhi: Centre for Science and the Environment. 36pp.
[6] p.380 in Gore,A. (1992) On stabilising world population. Population and Development Review. 18(2): 380-383. This article was extracted from his widely sold book, Earth in the Balance: Ecology and the Human Spirit (Houghton Mifflin, 1992).
[7] Wolfgang Lutz subsequently become one of the world’s leading demographers, founding in 2011, and then directing, the Wittgenstein Centre for Demography and Global Human Capital, a collaboration between IIASA, the Vienna Institute of Demography of the Austrian Academy of Sciences, and the University of Vienna.
[8] O’Neill,B. (2000) Cairo and climate change: a win-win opportunity. Global Environmental Change. 10: 93-96. In this same article, O’Neill nicely describes the ‘no-regret’ nature of population policies for climate: “Although the kinds of policies called for by the Program of Action are not primarily motivated by their potential elect on demographic trends, many of them would likely lead to lower fertility and slower population growth and, in turn, reduced human impact on the environment. Investments in these policies therefore make sense, not only because they would directly improve human welfare, but also because they would indirectly benefit the environment.”
[9] Michaelowa,A. (2002) Book review: ‘Population and Climate Change’ by O’Neill,B., MacKellar,L. and Lutz,W. (CUP, 2000). Climate Policy. 2(2-3):261-263.
[10] Dalton,M. (2002) Book review: ‘Population and Climate Change’ by O’Neill,B., MacKellar,L. and Lutz,W. (CUP, 2000). Climatic Change. 55: 409–412.
[11] Bongaarts,J. and O’Neill,B.C. (2018) Global warming policy: is population left out in the cold? Science. 361: 650-652.
