New study: Population growth cancelling progress on climate emissions

25 January 2021

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New study: Population growth cancelling progress on climate emissions

New peer-reviewed research finds that since 1990, more than three-quarters of the global reduction in carbon emissions achieved by increased energy efficiency and reducing carbon emissions from energy production have been cancelled out by the impact of a growing population.

Population effects of increase in world energy use and CO2 emissions: 1990 - 2019, by Prof Aalok Ranjan Chaurasia of the MLC Foundation in India, is published in the Journal of Population and Sustainability (1). The study examines the effects of four factors on total energy use and carbon dioxide emissions across 44 countries: population change, economic growth, energy efficiency (energy use/production per unit of GDP) and carbon efficiency (level of emissions per unit of energy) (2). Key findings include:

The main driver of CO2 emissions is economic growth, measured by per capita real GDP. Between 1990 and 2019, it accounted for two thirds of total increase in emissions (15,181 Mt CO2), with population accounting for one third (8,962 Mt).

Decrease in energy intensity of GDP produced far more emissions savings than decrease in carbon intensity - 11336 Mt and 377 Mt respectively during 1990-2019.

Over 77 per cent of the reduction in CO2 emissions that arose from the decrease in the energy intensity and carbon intensity has been offset by the increase in population.

More than two thirds of the global increase in energy use during 1990-2019 was confined to only five countries – China, India, United States of America, South Korea and Iran. These five countries accounted for more than 43 percent of the world population in 2019. 

More than 80 percent of the global increase in CO2 emissions was confined to only four countries – China, India, Iran and Indonesia. China, accounting for almost 19 percent of the world population in 2019, was responsible for almost 43 per cent of the global increase in the energy use and more than 60 per cent of the global increase in the CO2 emissions during 1990-2019. 

There are 11 countries where energy use decreased and 13 countries where CO2 emissions decreased during the period. The decrease in both energy use and CO2 emissions has been the most rapid in Ukraine while the increase in both energy use and emissions has been the most rapid in Malaysia.

The findings of the research are consistent with the work of Project Drawdown, a rolling study of available policy options for minimising emissions. Its analysis of 80 solutions for minimising emissions, ranging from plant-based diets to refrigerant management, concluded that empowering voluntary actions to achieve a low global population scenario based on UN projections would save 85Gt of emissions by 2050. This makes it the second most effective solution in limiting warming to 2°C and fifth most effective in limiting warming to 1.5°C - more effective than almost all popular technological solutions, including electric cars, and solar, offshore wind, wave and tidal power (3).

Prof Chaurasia says:

“There is a conspicuous silence in recent years about the role of population in the debate on environmental sustainability. For example, the United Nations 2030 Agenda for Sustainable Development pays only passing attention to population related issues and concerns in the quest to secure environmental sustainability. My analysis highlights the need to integrate population as a factor in environmental sustainability. The extensiveness, intensity and efficiency of natural resource use all interact with each other to determine the impact of the humanity on the environment. Reducing and ultimately achieving zero population growth can contribute significantly towards environmental sustainability by considerably decelerating the increase in energy use and CO2 emissions, although the implications of such a strategy are quite challenging.”

Commenting on the study, Robin Maynard, director of campaigning charity Population Matters, said:

“There are many drivers of climate change and all must be considered and mitigated. Addressing population or any of those drivers alone will not be enough. We need radical change across the board, exercising all options and available actions in behaviour - especially in the high-consuming Global North - policy and the economic system to achieve the Paris targets.

“However, this study demonstrates that if the driver of population is ignored then progress in other areas will be overwhelmed and even cancelled out. That progress is not limited to the significant impacts in cutting climate change emissions. Positive, ethical and effective solutions to population growth include enabling over 270 million women worldwide to have the choice, freedom and ability to use safe, modern family planning, which they want, but currently lack (4).  Hence, Project Drawdown’s founder, Paul Hawken, describing these climate and justice solutions of universal education for girls and access to family planning as ‘No Regrets’ solutions, benefitting people and planet.”






Alistair Currie, Head of Campaigns and Communications, Population Matters


T: +44 208 123 9170 (24hrs)


The author, Prof Chaurasia, may also be contacted via email at


Notes for editors

(1) Article citation: Chaurasia, A. R., 2020.  Population effects of increase in world energy use and CO2 emissions: 1990–2019. The Journal of Population and Sustainability,  5(1), pp.87-125 Available here.

(2) Definitions: Energy use has been defined as the balance of the primary energy production, external energy trade, marine bunkers and stock changes including biomass. Estimates of energy use for the world include marine bunkers also but they are not included while estimating energy use in different countries. Estimates of CO2 emissions are confined to emissions from fossil fuel combustion (coal, oil and gas) only. They have been estimated following the methodology proposed by the United Nations Framework Convention for Climate Change (UNFCCC, 2009). The energy efficiency of GDP has been calculated as the ratio of total energy use to real GDP which has been measured in terms of 2015 US$ purchasing power parity. Carbon intensity of energy use is measured as CO2 emissions per unit energy use.

(3) Project Drawdown Project Drawdown (2020) Sector Summary: Health and Education   

(4) A 2019 study by researchers at the United Nations Population Fund estimated the number of women who wish to avoid pregnancy but are not currently using modern birth control methods at approximately 270 million. This is a rise from 232 million women in 1990, and is likely to reach 272 million by 2030 due to rapid population growth and slow progress in improving access to modern contraceptive methods. Kantorová et al (2020) Estimating progress towards meeting women’s contraceptive needs in 185 countries: A Bayesian hierarchical modelling study, PLOS Medicine. Available here.

Published biannually, The Journal of Population and Sustainability is an open access, peer reviewed, interdisciplinary journal exploring all aspects of the relationship between human numbers and environmental issues. It is published by Population Matters but is editorially independent. 

The MLC Foundation is a voluntary research organisation that focuses on population and development interactions and their implications. The Foundation undertakes research to generate evidence to support integration of population factors in development planning and programming. 

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