1. Demographic Trends and Implications for Greenhouse Gas Emissions
Brian C. O’Neill
Institute for the Study of Society and Environment,
National Center for Atmospheric Research (NCAR)
&
International Institute for Applied Systems Analysis (IIASA)
GTSP Technical Review Workshop, JGCRI, College Park, Maryland
28 May 2008

2. Demographic Trends and Emissions Implications
Population size
Aging
Household Size
Urbanization
Implications for Emissions
Uncertainty, learning, and optimal emissions
Aging, urbanization, and national emissions
Global emissions effects?

3. Projecting Population Size: World
UN 2006 Range
Source: Lutz et al., 2008.

4. Projecting Population Size: World
SRES Range
UN 2006 Range
Source: Lutz et al., 2008.

5. Sub-Saharan Africa
UN 2006 Range
Source: Lutz et al., 2008.

6. Eastern Europe
UN 2006 Range
Source: Lutz et al., 2008.

7. China+
UN 2006 Range
Source: Lutz et al., 2008.

8. Population Projections
Source: Oppenheimer, O’Neill, & Webster, 2008.

9. People Living with HIV, by Region
Distribution, 2007
In 2007, an estimated 33.2 million adults and children worldwide were living with HIV.
Sixty-eight percent of the world’s HIV population lives in sub-Saharan Africa.
Slide from Population Reference Bureau
Note: Total exceeds 100 percent due to rounding.
Source: UNAIDS, AIDS Epidemic Update, December 2007.

10. South Africa’s Population With and Without AIDS
Millions
Slide from Population Reference Bureau
Source: United Nations, World Population Prospects: The 2006 Revision (CD-ROM Edition—Extended Dataset), 2007.

11. Age Distribution of the World’s Population
Population Structures by Age and Sex, 2005
Millions
Less Developed Regions
More Developed Regions
Age
0-4
Male
Female
Male
Female
Sex and age distributions show that less developed countries have significantly younger populations than more developed countries.
Almost one-third of the population in less developed countries is under age 15. In contrast, less than one-fifth of the population in more developed countries is under 15.
Today there are more than 2 billion young people below age 20 in less developed regions—the age cohort that will soon become the world’s newest group of parents.
Young age structures in the less developed countries are due mainly to higher levels of childbearing in recent decades.
Slide from Population Reference Bureau Source: United Nations, World Population Prospects: The 2004 Revision, 2005.

12. China’s Age Distribution
Population Structures by Age and Sex
Millions
1950
2000
2050
Age
Age
0-4
0-4
Male
Female
Male
Female
Male
Female
This figure illustrates China’s shrinking young and working-age population and growing elderly population.
Dramatic fertility decline (due to the success of the “one-child” policy) and improved longevity over the past two decades are causing China’s population to age at one of the fastest rates ever recorded.
China now faces the prospect of having too few children to support its rapidly aging population. Meeting the health and long-term care needs of this growing elderly population will result in soaring health care costs and fewer working-age people to share the burden.
Slide from Population Reference Bureau Source: World Population Prospects: The 2004 Revision (2005).

13. Aging in China
Percent of Elderly (65+) in China’s Population,
Due to vast improvements in health over the past five decades, life expectancy at birth has increased by two-thirds from 40.8 to 71.5 years between 1955 and 2005.
The percent of elderly in China is projected to triple from 8 percent to 24 percent between 2006 and 2050.
Because chronic health problems become more common in old age, China’s population aging has led to increases in the country’s prevalence of chronic disease and disability.
Source: World Population Prospects: The 2004 Revision (2005).

14. Ageing: Likelihood of 1/3 population 60+
Source: Lutz, Sanderson & Scherbov, 2008.

15. Projected Aging, Western Europe
Source: Lutz, Sanderson & Scherbov, 2008.

16. Speed of Population Aging in Selected Countries
Number of Years for Percent of Population Age 65 or Older to Rise from 7% to 14%
More developed countries
Less developed countries
Aging has proceeded more gradually in more developed countries than in less developed countries, affording these nations time to adjust to this structural change. Japan is the major exception, doubling its percent of population age 65 or older in just 26 years. Other countries in East and Southeast Asia (especially China, South Korea, Taiwan, and Thailand) are on a similarly rapid trajectory, fueled by dramatic and relatively recent drops in fertility.
* Dates show the span of years when percent of population age 65 or older rose (or is projected to rise) from 7 percent to 14 percent.
Source: K. Kinsella and Y.J. Gist, Older Workers, Retirement, and Pensions: A Comparative International Chartbook (1995) and K. Kinsella and D. Phillips, “The Challenge of Global Aging,” Population Bulletin 60, no. 1 (2005).

17. Alternative measures of aging, U.S.
Source: Sanderson & Scherbov, 2005.

18. Alternative measures of aging, World
Source: Lutz, Sanderson & Scherbov, 2008.

19. Urbanization, Global
Urban
Rural
Source: UN, 2007.

20. Urbanization, Industrialized & Developing
Rural
LDCs
MDCs
Source: UN, 2007.

21. Inverting UN Urbanization Projections
Source: O’Neill and Scherbov, 2007.

22. Inverting UN Urbanization Projections
Source: O’Neill and Scherbov, 2007.

23. Trends Summary Divergent trends in population size
Globally, less growth than previously expected
Aging everywhere, older in industrialized countries, faster in developing countries
Declines in household size in developing countries, trends unclear in industrialized countries
Urbanization in developing countries, projections not well developed

24. Implications for Emissions
Uncertainty and learning
Aging, urbanization, and national emissions
Toward global emissions implications

25. Population Learning: An Example
Source: O’Neill & Sanderson, 2008.

26. Managing Uncertainty: Preparing to Respond to New Information
Optimal emissions for stabilization at 600 ppm
Learning about outlook for future population growth occurs in 2020
Potential for outlook to shift to faster or slower population growth modeled using probabilistic projections
After 2020, substantial adjustments made to optimal emissions strategy depending on what is learned
Red lines: Learn in 2020
Emissions (GtC/yr)
Blue line: Total uncertainty (no learning)
Source: O’Neill & Sanderson, 2008.

27. Population and Emissions: The PET Model
Households
Consumption & Savings
Capital & Labor
Final Goods Producers
Consumption
Investment
Government
Exports & Imports
Intermediate goods producers
Oil&Gas
Coal
Electricity
Refined Petroleum
Materials
Labor
Capital
Final Goods
Energy
CO2 Emissions
Source: Dalton et al., 2008; Dalton & Goulder, 1998.

28. Labor Income Heterogeneity, China, 2000
Source: Dalton et al., 2008.

29. Expenditure Heterogeneity, China, 2000
Source: Dalton et al., 2008.

30. Effects of Aging and Urbanization on Chinese CO2 Emissions, B2 Scenario
No demography
Urb. + Aging + Size
Aging
Aging + size
Urbanization effect on emissions
Source: Dalton et al., 2008.

31. Effects of Aging and Urbanization on Indian CO2 Emissions, B2 Scenario
No demography
Urb. + Aging
Aging
Urbanization effect on emissions
Source: Dalton et al., 2008.

32. Effects of Aging on U.S. CO2 Emissions in 2100

33. Effects of Aging and HH Size Changes on U.S. CO2 Emissions in 2100

34. iPETS: Global, regionally disaggregated IA Model (Integrated Population-Economy-Technology-Science Model)
PET
Population Households
Producers
Labor, Land, Capital
Food and other goods
Terrestrial Ecosystems
Ocean, Sea ice, Atmosphere
LU Emissions
CO2 and Climate
Energy Emissions
Fertilizer use
Demand for Land
Supply of Land
ISAM
Collaborators: O’Neill (NCAR); Dalton (NOAA); Jain (U. Illinois); Jiang (Brown U.); Pachauri/Fuchs/Zigova (IIASA)