AerChemMIP is a joint contribution to CMIP6, organized by the co-chairs from AeroCom and CCMI. AerChemMIP will focus specifically on CMIP6-related science. It clearly follows from the experience gained in the CCMI and AeroCom simulations. AerChemMIP is designed to document and understand changes in aerosol and chemical constituents and associated forcings in CMIP6, in addition to help with providing input fields (e.g. ozone, oxidants, aerosols, nitrogen deposition) to climate models that do not have an explicit representation of atmospheric chemistry or aerosols.