Wrt (with respect to)

This selection determines the reference or baseline year or period from which the climate change scenario will be calculated. There are three options available: 1961-90 (the default), 1990 and 2000. 1961-90 is defined as the default period since it coincides with the period for which the baseline climatologies used in SCENGEN have been calculated. For consistency, therefore, the climate change should be calculated with respect to this 30-year period. The IPCC, however, in all their reports to date have adopted 1990 as the baseline year, i.e., their calculations of future climate change have been made with respect to the year 1990. This option is therefore included in SCENGEN if the user wishes to replicate the results of IPCC. It should be borne in mind, however, that when using a 1961-90 baseline climatology to define current conditions (as we do in SCENGEN) between 0.05deg and 0.2deg C of global warming may be 'missed' by choosing 1990 as the baseline year. The third option is to select the current year (2000) as the baseline and calculate climate change with respect to 'now'. When using a 1961-90 climatology to define the 'current' pattern of climate, however, this is an even more inconsistent choice than 1990.