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Online climate change projections report 5.2 RCM experiments

As mentioned above, and described in more detail in Chapter 3, transient (that is, continuous from 1950–2099) projections from GCM experiments were used as boundary conditions to drive transient regional climate model experiments. Only the Medium emissions scenario was used. Each RCM variant used parameter settings selected to be consistent with those used in the relevant driving GCM variant. In eleven RCM ensemble members this experimental design produced physically plausible simulations of detailed climate variability and change over the UK. In the case of an additional six ensemble members, however, the RCM simulations were found to be deficient in their simulations of storms and precipitation, because one of the parameter perturbations employed in the RCM failed to produce an impact consistent with that found in the driving GCM projections (details in Section 3.2.11). These members were therefore not used in the downscaling procedure for UKCP09, which was based on the remaining eleven RCM variants.

Daily data from 1950–2099 has been archived from each of these eleven variants, for a large number of variables (at the surface and at levels in the atmosphere) for 25 km grid squares over the domain shown in Chapter 3 Figure 3.8. Following interest from the user community, it was agreed to make this data available. This will be done via the Climate Impacts LINK project, a Defra-funded activity operated by the British Atmospheric Data Centre, which allows access for research to a range of data from model experiments undertaken at Met Office. Data accessed via LINK is not accompanied by extensive guidance.

Data from the RCM ensemble is also available as monthly and seasonal means. The RCM data can be used to create projections of climate change, by differencing averages for a future period from a reference period. This operation cannot be performed using the LINK website, but can be done offline once the data has been downloaded. Information on the use of this data is available in the UKCP09 User Guidance.

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