IPCC AR4 Hamburg#

The model simulations for the fourth IPCC Report, scheduled for early 2007, have been successfully completed by scientists from Max Planck Institute for Meteorology (MPI—M) and the Group “Model and Data” at the German Climate Computing Centre (DKRZ). In this Assessment Report No 4 (AR4) of the Intergovernmental Panel on Climate Change, IPCC (see also www.ipcc.ch), the actual knowledge on the state and the change of climate is integrated.

The simulations realized with a new climate model developed at MPI-M can be characterized as follows:

  • Reconstruction of an “undisturbed” pre—industrial climate

  • Climate change experiments forced with observed atmospheric greenhouse gas and aerosol concentrations since the middle of the 19th century

  • Scenario experiments of climate change based on different assumptions on future greenhouse gas and aerosol concentrations

  • CO2 sensitivity experiments (1% per year increase)

All simulations were done on the HLRE - the High Performance Computing System for Earth System Research - at DKRZ. About a quarter of the total resources were necessary in the last year to complete the simulations.

The model output is stored in a relational database and is available to scientists for analysis. The data are available from DKRZ’s long-term data archive as DKRZ’s contribution to the IPCC Data Distribution Centre. You can find the data access under Experiments.


The experiments and their results are described in “Climate Projections for the 21st Century”

(|(pdf)| English) (|(pdf)| German)


The available variables with gribcode, internal name, long name and unit are listed here.

The CMIP3/AR4 simulations show a mean global warming between 2.5 and 4.1 degrees Celsius until the end of this century - dependent on how much greenhouse gases are emitted into the atmosphere. One of the consequences: the seasonal varying sea ice decreases - the arctic could become ice free during late summer when the emissions will not be reduced.