Abstract
Abstract. The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) consists of a series of time slice experiments targeting the long-term changes in atmospheric composition between 1850 and 2100, with the goal of documenting composition changes and the associated radiative forcing. In this overview paper, we introduce the ACCMIP activity, the various simulations performed (with a requested set of 14) and the associated model output. The 16 ACCMIP models have a wide range of horizontal and vertical resolutions, vertical extent, chemistry schemes and interaction with radiation and clouds. While anthropogenic and biomass burning emissions were specified for all time slices in the ACCMIP protocol, it is found that the natural emissions are responsible for a significant range across models, mostly in the case of ozone precursors. The analysis of selected present-day climate diagnostics (precipitation, temperature, specific humidity and zonal wind) reveals biases consistent with state-of-the-art climate models. The model-to-model comparison of changes in temperature, specific humidity and zonal wind between 1850 and 2000 and between 2000 and 2100 indicates mostly consistent results. However, models that are clear outliers are different enough from the other models to significantly affect their simulation of atmospheric chemistry.
Highlights
The Coupled Model Intercomparison Project (CMIP) is a protocol for (1) systematically defining model simulations to be performed with coupled atmosphere–ocean general circulation models (AOGCMs) and (2) studying the generated output
We note that the RCP2.6 change for NCAR-CAM3.5 is considerably smaller than in the remaining models. Both issues are related to the use of the CCSM3 Commitment simulation to define the sea surface temperature (SST), it is exacerbated in CESM-CAM-Superfast by the fact that they used CCSM4 SSTs/sea ice concentration (SIC) for their 2000 time slice; these are warmer than CCSM3 and the specific humidity reflects an actual drop in temperature between year 2000 and year 2100
We discuss and compare the 16 models that participated in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)
Summary
The Coupled Model Intercomparison Project (CMIP) is a protocol for (1) systematically defining model simulations to be performed with coupled atmosphere–ocean general circulation models (AOGCMs) and (2) studying the generated output This framework provides the scientific community with the ability to more and meaningfully intercompare model results, a process which serves to facilitate model improvement. Concentrations (forcings) will differ between models due to different transformation/removal processes This is especially the case as models progress towards a more Earth System approach and represent interactions with the biosphere (Arneth et al, 2010a), including climate-sensitive emissions of isoprene (Guenther et al, 2006; Arneth et al, 2010b), methane ACCMIP Ozone Monitoring Instrument (OMI), the Moderate Resconsists of a set of numerical experiments designed to pro- olution Imaging Spectroradiometer (MODIS) on the Aura vide insight into atmospheric chemistry driven changes in the satellite, the Cloud-Aerosol Lidar and Infrared Pathfinder www.geosci-model-dev.net/6/179/2013/
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