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Population, Energy, and Emissions

Population Outlook

Today's world population is approximately 7.7 billion people and growing to a projected 9.6-10.9 billion in 2100.

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Recent trends suggest, however, that the UN may be underestimating future population growth in Africa 2. See our additional analysis of world population.

Future Energy Demand

The arrival of the Covid-19 pandemic had significant effect on energy demand.

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Change in key world energy metrics from 2019 to 2020, reflecting the impact of the COVID-19 pandemic. Published in October 2020. Source: 3.

The decline in energy demand may be temporary.

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Change in world energy consumption from 2019 to 2030, as estimated by the Stated Policies Scenario. Source: 3.

Before the pandemic, the IEA forecast energy and emissions to 2040 as follows.

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Population, GDP, energy, and emissions in 1990, 2018, and forecast in 2040, according to the IEA's STEPS (Stated Policies) scenario. Source: 4.

Energy Demand under Population Scenarios

World energy, both overall and on a per capta basis, has grown significantly over the last few decades.

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To estimate future energy demand, using the median UN population estimate, we consider what will happen if overall energy demand stays fixed, if per capita energy consumption stays fixed, if per capita energy consumption continues to grow linearly as it did from 1965-2014, if the average person in the future consumes like the average German today, and if the average person in the future consumes like the average American today.

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In the following, we examine the top eight energy-consuming countries in 2014, together with Africa. If the average UN population estimate holds in 2050 and the 1987-2017 trend in per capita energy consumption holds, the following energy consumption in 2050 is expected.

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Under this scenario, per capita energy forecasts will evolve as follows.

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Per capita energy consumption forecasts, derived from BP 5 and the UN 1.

Economic Energy Efficiency

In 2018, world GDP was estimated at about $121 trillion on a purchasing-power-parity (PPP) (2011 dollars) 6, 7. The economic energy efficiency of the world economy is the monetary output per unit energy, and this figure was over $200 per gigajoule in 2018. It has increased by over 50% since 1990, indicating both that more economic activity is generated for each unit of energy, and that efficiency is improving over time.

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World energy intensity. Derived from BP 8 and the World Bank 7.

The world economy may triple from 2015 to 2050 9. If the 1990-2018 average annual percentage increase in efficiency continues to 2050, then the world's energy will generate $312 per GJ, but the world energy demand will be 987 exajoules, nearly 70% more than today's value.

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Forecast GDP, energy demand, and energy efficiency to 2050. GDP figures are given by Pricewaterhouse Coopers 9 and energy figures from BP 8 and the World Bank 7.

Economic energy efficiency varies by country. The following shows efficiency for selected countries in 1990 and in 2018, using PPP.

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Evolution in energy intensity by country. Derived from BP 8 and the World Bank 7.

Economic energy efficiency is driven by several factors: technical efficiency, the design of cities, climate, personal behavior, and the composition of the economy 10. For individual countries, trade of energy-intensive products can affect observed efficiency 11. Some of the observed improvement in energy efficiency is the result of switching to higher quality fuels 12, 13. In general, the efficiency metric covers many factors that are unrelated to technical energy efficiency 14.

The above figures measure economic energy efficiency by considering modern forms of energy. The historical pattern is that efficiency tends to rise as a country industrializes, and after that it falls 15. However, if the energy inherent in biomass (e.g. crops, firewood) is also included, then the pattern is that energy intensity falls even in the early stages of industrialization 16, 15.

Kaya Metrics

Environmental impacts can be understood as the result of several forces: rising population and wealth tend to increase impacts, while improved technology decreases impacts. The IPAT (Impact = Population × Affluence × Technology) formula quantifies these three tendencies 17. Relatedly, greenhouse gas emissions from energy can be expressed with the Kaya identity: Emissions = Population × Affluence × Energy Intensity × Greenhouse Gas Intensity of Emissions 18. World trends since 1990 are as follows.

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Kaya decomposition of world greenhouse gas emissions from energy from 1990 to 2018. Population figures are from the UN 19. World GDP figures are taken on a purchasing power parity basis and derived from the World Bank 20. Energy is taken as primary energy and reported from BP 8. Only greenhouse gas emissions from energy are considered, and emissions are also taken from BP. All times series are scaled so as to have a value of 1 in 1990.

Compared to the world, the United States has seen slower population and GDP growth and faster improvements to energy intensity and carbon intensity of energy. As a result, US emissions appear to have peaked in 2007 and are close to 1990 levels.

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Kaya decomposion of United States greenhouse gas emissions from energy from 1990 to 2018. Population figures are from the UN 19. World GDP figures are taken on a purchasing power parity basis and derived from the World Bank 20. Energy is taken as primary energy and reported from BP 8. Only greenhouse gas emissions from energy are considered, and emissions are also taken from BP. All times series are scaled so as to have a value of 1 in 1990.

Energy intensity is driven by several factors: technical efficiency, urban design, climate, personal behavior, and the composition of the economy 10. For individual countries, trade of energy-intensive products can affect observed intensity 11. Some of the observed improvement in intensity is the result of switching to higher quality fuels 12, 13. In general, the efficiency metric covers many factors that are unrelated to technical energy efficiency 14.

On a world basis, factors other than energy intensity become somewhat less important than on a national basis.

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Contributions to world energy consumption growth from 1990 to 2010, estimated by Lan et al. 21.

References

  1. United Nations, Department of Economic and Social Affairs, Population Division, Population Estimates and Projections Section. "World Population Prospects: The 2017 Revision". Accessed April 18, 2019. ↩ ↩2 ↩3 ↩4 ↩5

  2. Gerland, P. et al. "World population stabilization unlikely this century". Science 10 Vol. 346 no. 6206 pp. 234-237. October 2014. ↩

  3. International Energy Agency. "World Energy Outlook 2020". Part of World Energy Outlook. October 2020. ↩ ↩2

  4. Newell, R., Raimi, D., Villanueva, S., Prest, D. "Global Energy Outlook 2020: Energy Transition or Energy Addition?". Resources for the Future, Report 20-05. May 2020. ↩

  5. BP. "Statistical Review of World Energy 2018". 2018. ↩ ↩2 ↩3 ↩4

  6. Callen T. "PPP Versus the Market: Which Weight Matters?". Finance and Development, International Monetary Fund. March 2007. ↩

  7. World Bank. "GDP, PPP (constant 2011 international $)". Accessed April 24, 2019. ↩ ↩2 ↩3 ↩4

  8. BP. "Statistical Review of World Energy 2019". 2019. ↩ ↩2 ↩3 ↩4 ↩5

  9. Hawksworth, J., Chan, D. "The World in 2050: Will the shift in global economic power continue?". February 2015. ↩ ↩2

  10. U.S. Department of Energy, Office of Renewable Energy & Energy Efficiency. "Energy Intensity Indicators: Highlights". Accessed July 9, 2015. ↩ ↩2

  11. Nelder, C. "The Worst Way to Measure Energy Efficiency". Slate. ↩ ↩2

  12. Kaufman, R. "The Mechanisms for Autonomous Energy Efficiency Increases: A Cointegration Analysis of the US Energy/GDP Ratio". Energy Journal 25 (1), pp. 63-86. January 2004. ↩ ↩2

  13. Stern, D. "Modeling International Trends in Energy Efficiency and Carbon Emissions". Environmental Economics Research Hub Research Reports, Research Report No. 54. March 2010. ↩ ↩2

  14. U.S. Department of Energy, Office of Renewable Energy & Energy Efficiency. "Energy Intensity Indicators". Accessed March 27, 2019. ↩ ↩2

  15. Stern, D. "The Role of Energy in Economic Growth". Centre for Climate & Economics Policy, Working Paper 3.10. October 2010. ↩ ↩2

  16. Ayres, R., Warr, B. "Accounting for Growth: The Role of Physical Work". Structural Change and Economic Dynamics, 16(2), pp. 181-209. June 2005. ↩

  17. Chertow, M. "The IPAT Equation and Its Variants". Journal of Industrial Ecology 4(4), pp. 13-29. October 2000. ↩

  18. Kaya, Y., Yokoburi, K. Environment, energy, and economy : strategies for sustainability. United Nations Univ. Press. ISBN 9280809113. March 1998. ↩

  19. United Nations, Department of Economic and Social Affairs, Population Division, Population Estimates and Projections Section. "World Population Prospects 2019". Accessed June 29, 2020. ↩ ↩2

  20. World Bank. "GDP, PPP (constant 2017 international $)". Accessed June 29, 2020. ↩ ↩2

  21. Lan, J., Malik, A., Lenzen, M., McBain, D., Kanemoto, K. "A structural decomposition analysis of global energy footprints". Applied Energy 163, pp. 436-451. February 2016. ↩