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Questions related to components and mechanisms influencing the climate such as greenhouse gas content of the atmosphere, aerosol particle concentrations, land-use changes and how these are incorporated into the climate models. Different generations of scenarios and how comparable these are also part of this topic. |
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Are future forcing conditions considered similarly in
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regional climate models as in
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global climate models?
Consistency facilitates interpretation of the results if forcing is the same in global and regional climate models and if it is treated in a similar way. In practice, however, details in the models differ and thereby forcing is often treated differently. This applies also for CORDEX regional climate model projections provided by the C3S.
Examples of differences include different radiation schemes that result in different treatment of both greenhouse gases and aerosols. For instance, some regional climate models have simplified radiation schemes where several greenhouse gases are lumped together and treated as CO2-equivalents instead of separately calculating the impacts of the different greenhouse gases (e.g. CO2, CH4, N2O, etc.). Further, many CORDEX regional climate models have a more simplified treatment of aerosols compared to their driving global models and thereby changing aerosol concentrations are not always included in the RCMs. Consequently, this may lead to different results as shown for Europe by e.g. Boé et al (2020). Land-use is another feature that may differ between GCMs and RCMs and in most of the EURO-CORDEX RCM projections in C3S_34b_Lot2 land-use is not evolving with time. Further information about the details of some of the RCMs can be found at https://search.es-doc.org/?project=cordexp
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It is suggested that users of regional climate information carefully evaluate whether such differences in forcing are of relevance for their specific questions.
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