GCMs

Select GCMs

The GCMs sub-menu displays details of the various geographical patterns of climate change available for the user to select. They are divided into 'GHG change patterns' and 'SO4 change patterns', the latter refering to the effects of sulphate aerosols. Each set of GCM patterns derives from a specific climate change experiment whose acronym and full name are given. The buttons on the right-hand side of the GCMs menu provides background information for each GCM experiment (use the scroll-bar if not all the GCMs are visible on your monitor).

The GCM patterns are listed in rank order according to a pattern correlation statistic which describes how well the mean monthly global (land and ocean) precipitation patterns in the control simulation of the experiment reproduced the observed (Legates & Willmott) global pattern of mean monthly precipitation. Experiments at the top of the list (pattern correlation of 0.76) performed better than those at the bottom (pattern correlation 0.59). Although this is only one out of a large number of possible model validation statistics, it does provide some basis for assessing how 'good' the respective model may be.

Depending on which VARIABLE the user has chosen, some of the GCM patterns may not be available for selection. This will be indicated by GCM labels being shown in subdued text. For these GCMs and for this variable, the change patterns are not available.

Aerosol Patterns

Aerosol patterns are held for three global sub-regions: North America and Europe; Eastern Asia; and the Rest of the World. These regions correspond to the three regions for which MAGICC calculates aerosol contributions to global temperature change. The aerosol patterns in this version of SCENGEN derive from a set of experiments performed by Mike Schlesinger at UIUC with his slab ocean model, in which aerosol loadings were introduced region-by-region for each separate experiment. The six Schlesinger regions have been re-aggregated into the three SCENGEN regions.

As with the greenhouse gas patterns, each regional aerosol pattern is standardised by the global-mean temperature. This allows the aerosol patterns to be scaled by global temperature calculations from MAGICC and then re-combined with greenhouse gas patterns to yield an overall greenhouse gas and aerosol forced climate change scenario.

Composite GHG Patterns

It is possible to select patterns from more than one GCM. If this is done then a composite GCM climate change pattern will be calculated using the average of the patterns from the selected GCMs. The default setting of SCENGEN is for *all* GCM patterns to be selected. This default selection can be switched off using the button on the first line of the Select GCMs menu.