Review of the global models used within the Chemistry-Climate Model Initiative (CCMI)

Abstract

We present an overview of state-of-the-artchemistry–climate and chemistry transport models that areused within phase 1 of the Chemistry–Climate Model Initia-tive (CCMI-1). The CCMI aims to conduct a detailed evalua-tion of participating models using process-oriented diagnos-tics derived from observations in order to gain confidence inthe models’ projections of the stratospheric ozone layer, tro-pospheric composition, air quality, where applicable globalclimate change, and the interactions between them. Interpre-tation of these diagnostics requires detailed knowledge of theradiative, chemical, dynamical, and physical processes incor-porated in the models. Also an understanding of the degree towhich CCMI-1 recommendations for simulations have beenfollowed is necessary to understand model responses to an-thropogenic and natural forcing and also to explain inter-model differences. This becomes even more important giventhe ongoing development and the ever-growing complexityof these models. This paper also provides an overview ofthe available CCMI-1 simulations with the aim of informingCCMI data users.