Whatever the ‘personal reasons’ that compelled Green to take leave of absence were, they apparently won’t stop him from diving into new ventures; according to the press release, Nokia’s former CTO, who was appointed to that role in May 2010, “will be returning full time to the U.S. to pursue new opportunities”.
Green is also no longer a member of the Nokia Leadership Team, to which he was appointed in February 2011.
Tirri joined Nokia in 2004 as a Research Fellow before leading NRC Systems Research laboratory in 2007. Interestingly, Tirri will be based in the United States, more specifically in Sunnyvale, California, a major city in Silicon Valley. He reports directly to Nokia CEO Stephen Elop.
Tirri holds a Ph.D. in Computer Science from the University of Helsinki, Finland.
Bonus link: CrunchGear interviews Tirri back in 2008.