Today I was checking my playing history and I noted the ranking history rating does not correspond with the global ranking. Should it correspond or is it calculated a different way?

I believe the Ranking Score with the settings of Public-Regular-Normal on Player Stats ( http://www.wargear.net/players/info/Luieuil/Player%20Stats ) should be the same as your Global Ranking Score, which right now both appear to be 2651 for you.  Different settings (ie Private/Teamplay/Tournament) would calculate a different score.

Are those the numbers you're asking about?