CMIP5 daily data on single levels

This catalogue entry provides daily climate projections on single levels from a large number of experiments, models, members and time periods computed in the framework of fifth phase of the Coupled Model Intercomparison Project (CMIP5). Information on how to access the complete CMIP5 dataset can be found in the Documentation section.

The term "single levels" is used to express that the variables computed at multiple vertical levels are excluded from this catalogue entry. The term "experiments" refers to the four main categories of CMIP5 simulations:

• Historical experiments which cover the period where climate observations exist. These experiments can be used as a reference period for comparison with scenario runs for the future. The period covered is typically 1850-2005.;
• Ensemble of experiments from the Atmospheric Model Intercomparison Project (AMIP), which prescribes the oceanic variables for all models and during the all period of the experiment. This configuration removes the added complexity of ocean-atmosphere feedbacks in the climate system. The period covered is typically 1950-2005.
• Ensemble of climate projection experiments following the Representative Concentration Pathways (RCP) 2.6, 4.5, 6.0 and 8.5. The RCP scenarios provide different pathways of the future climate forcing. The period covered is typically 2006-2100.

Typically, the same experiment was done using different models. In addition, for each model, the same experiment was repeatedly done using slightly different conditions producing in that way an ensemble of experiments closely related. Each member of that ensemble is named after a triad of integers associated to the letters r, i and p. These three letter cover variations in initial conditions and dates as well as in the physical parameters of the models. The associated numbers are typically assigned sequentially. For instance, the member "r1i1p1" and the member "r1i2p2" for the same model and experiment indicate that the corresponding simulations differ since the initial conditions and the physical parameters of the model for the second member were changed relatively to the first member.

CMIP5 data were used extensively in the Intergovernmental Panel on Climate Change 5th Assessment Report (IPCC AR5) which was published in September 2009. The use of these data is often aimed at:

• addressing outstanding scientific questions that arose as part of the IPCC AR4 (the Intergovernmental Panel on Climate Change 4th Assessment Report) process;
• improving the understanding of climate;
• providing estimates of future climate change that will be useful to those considering its possible consequences;
• determining why similarly forced models produce a range of responses;
• assessing the mechanisms responsible for model differences in poorly understood feedbacks associated with the carbon cycle and with cloud;
• examining climate predictability and exploring the ability of models to predict climate on decadal time scales;
• evaluating how realistic the different models are in simulating the recent past.

More details about the product are given in the Documentation section.