It’s Friday night at Portland’s Wonder Ballroom, and the band onstage isn’t old enough to attend its own show. About a hundred fans casually swill beer from plastic cups, but it will be seven years before Katie Alto and Úna Rose—otherwise known as the duo Blübird—can drink legally. Hell, they haven’t even started high school yet.

Úna Rose, the 14-year-old lead singer and guitarist, stands with a straight back, her legs slightly scissored. Confident and calm, she stares directly into the eyes of audience members as she strums her sea green guitar. Behind her, Katie Alto, 13, pounds away at her drums, her chin angled toward her chest so that her dark brown bangs fall in front of her face. A disco ball hanging from the high, vaulted ceiling sends spots of light, like schools of little silver fish, swimming across the historic former dance hall.

Between songs, it’s Alto who handles most of the stage banter, and the minute she lowers her drumsticks, her demeanor changes entirely. No longer the cool, aloof musician, she suddenly becomes—well, a kid. She brushes her hair out of her eyes and smiles wide, revealing metal braces on both rows of teeth. Then, in a voice that’s still high and girlish—ending half her statements with a rising inflection, as if she were really asking a question—she introduces the next song, the song that has made Blübird both celebrated and reviled on radio shows and websites across the country.

“This one’s called ‘Global Warming,’ and it’s an original? It’s gotten a lot of controversy lately, like on talk shows? But we wrote it, and it’s what we believe. So, yeah.”

At this point, the crowd drifts closer to the stage, and scattered whoops and whistles soar toward the band. The song’s poppy bounce and minimalist instrumentation provide an apt backdrop for its simple lyrics: “Please don’t melt our glaciers/Please don’t kill us all,” Rose sings in a punky, almost staccato singsong. “Please don’t destroy our atmosphere/The sun will kill us all.”

One line in particular from this earnest environmental appeal leaves no one in doubt where Rose and Alto stand: “Bush is such an idiot!” the girls chime in unison, their voices sweet but vehement. And the crowd goes wild.

When Blübird first took flight two years ago, it seemed like any other band to come out of the much-publicized Rock ’n’ Roll Camp for Girls, the Northeast Portland institution that helps young girls get in touch with their inner riot grrrl through music lessons and workshops in everything from self-defense to zine-making. As with girl bands who came before it, Blübird would likely play a few shows around town, then break up in the wake of waning interest and the onset of adolescence. But that changed soon after the band formed, when Rose sent a home video of herself playing and talking about her song “Global Warming” to the producers of The Music in Me, an HBO miniseries about kid musicians.