Rising Air-Conditioning Use Intensifies Global Warming

Summary

Integrated assessment frameworkThis study develops an integrated assessment framework to quantify the total warming impact and inequalities resulting from AC use under various climate scenarios (see Fig. 6). For this scenario analysis, we utilize the SSP-RCP framework to simulate climate scenarios, matching the outputs of multiple GCM models from the CMIP6 database (see the Climate scenarios section). Subsequently, we quantify global and regional cooling demand across different scenarios using an improved population-weighted CDD approach, incorporating the heat-index approach (see the heat-index approach section). We integrate the improved regional CDDs as climate inputs into a widely used integrated assessment model GCAM19,66, enhancing the ability to project future AC energy consumption and associated GHG emissions. Additionally, by assessing AC-related impacts within GCAM across five IPCC-endorsed SSP-RCP scenarios, our findings provide a comprehensive outlook on future AC energy use and emissions under possible ranges of global warming trajectories and socio-economic development. Lastly, we assess the inequality in the use of air-conditioning using Gini coefficients and quantify the cooling gaps with an econometric model. The formulas used for the inequality assessment are presented below, with additional robustness analysis for the econometric model provided in the Supplementary Information. Finally, we employ the MAGICC model to evaluate the additional warming effects resulting from the GHG emissions associated with AC use. Detailed information is provided at the end of the “Methods” section.Fig. 6: Research framework of this study.The red circle represents the total warming impact from AC use. The content within the ellipse represents the key steps and components of the comprehensive assessment of air-conditioning, while the content within the boxes outlines the key methodologies employed to achieve the main objectives of this study.Climate scenariosIn our re...