Hi Len,
I really think that teaching users this very basic web browser skill about how to open links in a new tab or window is the best solution. Once a user knows how to use a web browser then it becomes annoying when a site opens a new window that I did not intend to open.
However there are ways of opening external links with javascript/jquery for those who think this is a good idea, I'm just not one who thinks that.
Not sure it can work for google ads though since those are coming from javascript also.
Best,
Joe