“Vampire Diaries” star/environmental activist Ian Somerhalder was in Boston on Tuesday to finish shooting “Years of Living Dangerously,” a docu-series about climate change that will air on Showtime next year. After Somerhalder posted his whereabouts on Instagram and Twitter, local fans responded with excitement, including Allie Raich, who asked, “Ian Somerhalder is somewhere in Boston. How am I supposed to go to class??,” and Tiaundra Loren Smith, who tweeted, a bit more emphatically, “Ian Somerhalder is in Boston!!!!! Ahhhhghhhhhhhhhh!!!!!” We’re sure those ladies are just excited about environmentalism. “Years of Living Dangerously” will also feature Jessica Alba, Olivia Munn, Boston’s own Matt Damon, and, according to the Internet Movie Database, former Red Sox star Nomar Garciaparra. During Somerhalder’s visit, he stopped by Cheers and posed for a photo with hostess Allix Kallini. She reports that he kissed her on the head — and that she might not wash her hair for a while.