Implications of shrinking household sizes for meeting the 1.5 °C climate targets

Understanding social trends such as shrinking household sizes plays an important role for designing effective policies to limit global warming to 1.5 °C and reach net-zero by 2050. Prior, cross-sectional work shows that larger households tend to have lower per capita carbon footprints and energy use due to sharing of living space and resources. However, we lack longitudinal studies that examine whether dwindling household sizes globally increase carbon footprints and create additional pressure for mitigation efforts in the future. We use data from 43 countries between 1995 and 2015, representative of 63% of the population and 80% of the carbon footprint globally in 2015. If household sizes had stayed at their 1995-levels, cumulative emissions between 1995 and 2015 would have been about 11.3 GtCO2eq lower. We project per capita total carbon footprints for 2030, showing that more household sharing could make a contribution to curbing emissions. This contribution, along other sustainable degrowth interventions, can produce substantial emission reductions necessary for achieving 1.5 °C compatible reduction targets for 2030. We further quantify some of the key socio-economic influences behind the household dynamics to discuss policy options for increased inter- and intra-household sharing.