Aerosols and Chemistry in the CMIP6 models – new science from AerChemMIP

Phase six of the Coupled Model Intercomparison Project (CMIP6) was the first CMIP to include significant numbers of climate models with interactive aerosols and chemistry. The AerChemMIP project was designed to understand the effects of interactive representation of aerosols and chemistry in model simulations of the past and future climate, and also to take advantage of this to further our fundamental understanding of aerosol and chemistry processes in the climate system.

The four science objectives of AerChemMIP were:

• How have anthropogenic emissions contributed to global radiative forcing and affected regional climate over the historical period?
• How might future policies (on climate, air quality and land use) affect the abundances of NTCFs and their climate impacts?
• How do uncertainties in historical NTCF emissions affect radiative forcing estimates?
• How important are climate feedbacks to natural NTCF emissions, atmospheric composition, and radiative effects?

 

The AerChemMIP project has already led to more than 15 published papers. These advanced our knowledge in: the evolution of aerosol and chemical processes over the historical period, the contributions of these species to past radiative forcing and climate and their effect on future climate, and the impacts of different scenarios for future atmospheric composition and air quality. These have all made significant contributions to the IPCC 6^th Assessment Report. We show that including interactive aerosols and chemistry in climate models is crucial to simulating past and future climates, provided we understand the behaviour of the fundamental processes.