These two ERCA lectures will give a broad overview about the general methods, current scientific approaches and latest technical development of global climate modelling.

In the first lecture, different types of climate modelling approaches ranging from simple box models to highly complex general circulation models are presented. According to the general focus of ERCA, emphasis is set on different types of atmospheric climate models. Advantages and disadvantages of the different approaches are discussed. The physical principles underlying all calculus of all the different models, i.e. the so-called fundamental equations, are explained in detail. Next, the general challenge of spatial and temporal discretization of the fundamental equations is described. Some related mathematical tools for discretizing the relevant partial differential equations are briefly discussed. Besides discretization, a realistic representation of sub-scale processes and the quasi-simultaneous computation of many different physical processes are among the most difficult problems in climate modelling. Both problems and some potential solutions to them will be presented in detail at the end of the first lecture.

The second lecture will start with an in-depth scientific example to demonstrate the advantages of complex general circulation models (GCM) as compared to simpler modelling approaches. Among others, the example will show, how GCM simulations might help to interpret observational data sets and rule out competing hypotheses of interpretation. In a next step, the most recent development shift from physical-based climate models to more integrative Earth System Models is explained. An overview of recent and envisioned improvements of future model development is given and some examples of the latest improvements in parameterizations and spatial resolution are presented. It is shown, how the latter progress is directly related to the steadily increasing available computing power. Potential future problems and limitations of this technical advancement are discussed. In the final part of the second lecture, a summary of the latest simulation results on past, present and potential future climate change, as published by the International Panel on Climate Change (IPCC), is presented.

Literature Recommendations (ordered by publication date):

• Kendal McGuffie and Ann Henderson-Sellers, A Climate Modelling Primer, John Wiley & Sons Ltd., 2005.
• Masaki Satoh, Atmospheric Circulation Dynamics and General Circulation Models, Springer Verlag / Praxis Publishing Ltd., 2004.
• Walter A. Robinson, Modeling Dynamic Climate Systems, Springer-Verlag, 2001.
• Hans von Storch, Stefan Güss and Martin Heimann, Das Klimasystem und seine Modellierung, Springer-Verlag, 1999 (in German, only).
• Kevin E. Trenberth, Climate System Modeling, Cambridge University Press, 1993.

Lecture Material (PDF Format)

1. Basic Concepts & Approaches of Global Climate Modeling (4.4 MB)
2. Current Status & Limitations of Earth System Models (4.9 MB)