The four options shown by SCENGEN relate back to values used by MAGICC and are: high (deltaT2x = 4.5degC), mid (2.5degC), low (1.5degC) and user (user-defined). If the user did not make a user selection for the climate sensitivity in MAGICC, then the user-defined value will be 2.5degC, the mid-range value specified by IPCC. As the user clicks on different values of this parameter, the global-mean deltaT value (highlighted in red), which corresponds to the actual warming for the selected time interval, will change accordingly.
Note that the User climate sensitivity can only be selected when the User set of MAGICC PARAMETERS has been selected first.