I am wondering wether it is possible to remove a common part from all existing Appointments in my google calender matching a given pattern:
AE [0-9][0-9][0-9][0-9][0-9]-[0-9] [0-9]S:
AE 12345-4 2S xxxxxx
Its all the same length the begin with, just remove the first 14 characters. If its variable, you might want to move it all to excel, text to columns by S, just take everything in the second and later columns. Note: this requires exporting the calendar to a .csv first.
You're not indicating which OS's you have available, but an easy solution would be to use AppleScript in OSX. This assumes you have configured your Google Calendar in iCal (in 10.8 Mountain Lion known as Calendar) over CalDav so that you can edit the calendar.