Climate modelling
Our Climate System is driven by a number of so called "Climate stimuli". Most important is the sun, beeing the main energy source for earth´s climate system. In addition, there are other´s: For example, there are the greenhouse gases which have a warming effect on the climate or aerosols, which tend to have a cooling effect. Aerosols can be produced by humans, but some also have a natural origin. The history of climate with it´s changes between glacial and warm periods is driven by the interaction of the different stimuli.
At the moment, we are facing a rise of global mean temperature, whereas the changes in temperature can be very different on a regional scale. The scientific community assumes that a part of the global rise of temperature has it´s origin in human behaviour. Mainly due to the emission of greenhouse gases like carbondioxide or methan, but also because of extensive changes in landuse in the last centuries (IPCC AR5 2013). Opinions differ about the exact amount. Nevertheless, the rise of temperature in the course of the century is certain. For us as a society, it is therefore of great importance to assess the possible changes in the climate system in the next years and decades.
The tools for doing this are global climate models, also called GCM´s. They are mathematical models, simulating the processes in earth´s atmosphere. The first GCM´s were only atmospheric models, used for simulating the general circulation of the atmosphere. The newest generation is much more: Atmospheric-, ocean-, iceshield-, vegetation- and landmodels are interacting, trying to simulate all processes happening in earth´s system. Therefore they are not just GCM´s, but earth-system-models. This is done, by diving a grid with a horizontal gridsize between 100 and 200 kilometers, sometimes better. The atmosphere and oceans are also split up into 20 - 40 slices, depending on the model. The result is a threedimensional grid, in which all processes of the atmosphere, like wind, cloudformation, precipitation, transport of energy and all exchange-processes with land-, ocean-surface and vegetation are calculated by the use of mathematical equations. Even time is divided into slices of several minutes each. The smaller the timeslices and higher the resolution of the grids are, the bigger is the amount of needed computing-power.
A resolution of 100 km is far not enough for alpine regions with it´s complex topography to simulate all relevant processes. Therefore, Regional Climate Models (RCM) are used for simulating smaller clippings of earth with higher resolution, like 10 km for the model which has been used in this project. They receive information about the world outside their borders from the GCM´s and use it to calculate the atmospheric processes inside. With climate models it isn´t possible to make exact statements. But their predictions in many processes are very close to the measurements.
The maps and graphics in the climate modelling-part of this website are from the regional climate model CCLM, using the A1B-scenario with a resolution of 10 km. More information about climate modelling and it´s uncertainties can be found on the websites of the IPCC and APCC.
References:
IPCC AR5 (2013) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (Hrsg.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pages.