The IPSL-CM5 Earth System Model is used to study climate change projections under CMIP3 and CMIP5. It includes an interactive carbon cycle, atmospheric chemistry, and aerosol representation. The model is a comprehensive Earth System Model (ESM) that can be configured with various boundary conditions and complexities. It simulates historical climate changes over 150 years and future climate scenarios. The model provides climate projections based on socio-economic scenarios, including RCPs and SRES scenarios. Results indicate that global warming projections depend on the scenario, and aggressive mitigation could limit warming to about 2°C. Some climate components, like Arctic sea ice and Atlantic Meridional Overturning Circulation, may change drastically by the end of the century under no climate policy. Regional temperature and precipitation changes are linearly related to global warming, but their geographical patterns are similar across scenarios. The model's atmospheric processes significantly influence climate variability and projections. The IPSL-CM5 model includes various components, such as the atmosphere, stratospheric chemistry, tropospheric chemistry, and aerosols. It also includes a land surface model (ORCHIDEE) and ocean and sea-ice models. The model is coupled with ocean carbon cycle models and has been tuned to improve accuracy. The model's horizontal resolution is adjusted for different simulations. Ozone concentrations are modeled with different scenarios, showing variations in ozone levels over time. Aerosol concentrations are also modeled, with different scenarios affecting their impact on climate. The model's performance is evaluated against historical data and future projections, showing biases that need to be addressed. Overall, the IPSL-CM5 model provides valuable insights into climate change projections and the interactions between different components of the Earth system.The IPSL-CM5 Earth System Model is used to study climate change projections under CMIP3 and CMIP5. It includes an interactive carbon cycle, atmospheric chemistry, and aerosol representation. The model is a comprehensive Earth System Model (ESM) that can be configured with various boundary conditions and complexities. It simulates historical climate changes over 150 years and future climate scenarios. The model provides climate projections based on socio-economic scenarios, including RCPs and SRES scenarios. Results indicate that global warming projections depend on the scenario, and aggressive mitigation could limit warming to about 2°C. Some climate components, like Arctic sea ice and Atlantic Meridional Overturning Circulation, may change drastically by the end of the century under no climate policy. Regional temperature and precipitation changes are linearly related to global warming, but their geographical patterns are similar across scenarios. The model's atmospheric processes significantly influence climate variability and projections. The IPSL-CM5 model includes various components, such as the atmosphere, stratospheric chemistry, tropospheric chemistry, and aerosols. It also includes a land surface model (ORCHIDEE) and ocean and sea-ice models. The model is coupled with ocean carbon cycle models and has been tuned to improve accuracy. The model's horizontal resolution is adjusted for different simulations. Ozone concentrations are modeled with different scenarios, showing variations in ozone levels over time. Aerosol concentrations are also modeled, with different scenarios affecting their impact on climate. The model's performance is evaluated against historical data and future projections, showing biases that need to be addressed. Overall, the IPSL-CM5 model provides valuable insights into climate change projections and the interactions between different components of the Earth system.