Relations between demographic change and emissions of the major greenhouse gas CO2 have been studied from different perspectives, but most projections of future emissions only partly take demographic influences into account. We review two types of evidence for how CO2 emissions from the use of fossil fuels are affected by demographic factors such as population growth or decline, ageing, urbanisation, and changes in household size.

First, empirical analyses of historical trends tend to show that CO2 emissions from energy use respond almost proportionately to changes in population size and that ageing and urbanisation have less than proportional but statistically significant effects. Second, scenario analyses show that alternative population growth paths could have substantial effects on global CO2 emissions several decades from now, and that ageing and urbanisation can have important effects in particular world regions. These results imply that policies that slow population growth would probably also have climate-related benefits.

Key messages
  • Carbon dioxide (CO2) emissions from energy use respond almost proportionately to changes in population size
  • Ageing and urbanisation each have less than proportional, but statistically significant effects on CO2 emissions
  • Alternative population growth paths could lead to changes in global emissions of CO2 by about 15% by 2050 and 40-60% by 2100
  • Ageing could reduce future CO2 emissions by up to 20%,
  • and urbanisation could increase them by more than 25% in particular world regions
  • Policies that slow population growth are likely to have climate-related benefits

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