16 September 2013

New Internationally Coordinated Climate Model Experiments Underway


For more than two decades now, climate modeling groups have compared, evaluated, and made model projections under common experimental protocols (commonly referred to as "model intercomparison projects").  The World Climate Research Programme's Working Group on Coupled Modelling (WGCM) is responsible for some of the most ambitious activities of this kind, which are largely managed by the BER-sponsored Program for Climate Model Diagnosis and Intercomparison (PCMDI) at Lawrence Livermore National Laboratory.  Modeling groups are now providing new experimental results from the 5th phase of the Coupled Model Intercomparison Project (CMIP5).  In the Bulletin for the American Meteorological Society, leaders of the CMIP project have published a summary of the CMIP5 experiment design, along with guidance for accessing and making use of CMIP5 model output.


Building on earlier CMIP phases, CMIP5 includes a wider variety of simulations, which enables more thorough assessment of the models, facilitates forcing and feedback diagnosis, and provides projections covering a range of representative pathways for the evolution of greenhouse gases (see figure).  For the first time, some of the CMIP models include an interactive carbon cycle.  New experiments are called for which promise to provide better understanding of the extent to which observed ocean conditions determine climate changes occurring on decadal time scales. 

An exceptionally comprehensive set of model output is being collected and archived in a distributed database that users can access through portals and data interfaces developed by the DOE-led Earth System Grid Federation. A diverse cadre of international scientists is now analyzing the CMIP5 simulation.  Some of these scientists have only a limited understanding of climate models, so in the published journal article, guidance is provided to help non-experts avoid misinterpreting the CMIP5 experiment results.


The CMIP5 experiments are producing a freely available state-of-the-art multimodel dataset designed to advance our knowledge of climate variability and climate change.  The research articles based on the CMIP5 simulations are expected to underlie the new climate science to be evaluated in the IPCC’s fifth assessment report, scheduled for publication in late 2013.