This year's event drew a much smaller, but passionate crowd of a few hundred science buffs and practitioners to check out the booths run by science organizations and hear speeches and live music.
Many were scientists, like Becky Mackelprang of UC Berkeley. Mackelprang says she came to fight the growing mistrust of scientists and science, not just in terms of climate change, but also things like vaccines and "fake studies" shared on social media.
"I saw these two ridiculous studies, one was that thinking makes you fat and [the other was] that bras give you cancer," Mackelprang said. "What I would love was for the average person to see that headline and say, 'That doesn't seem right to me. Maybe I need to look into that a little bit more before I share it on Facebook.' "
Sprinkled among the scientists were their admirers, including a contingent of students there to support their biology teacher, Glenn Wolkenfeld, who was also lead singer of the band that opened the event.
Berkeley High School junior Colleen Burns says Wolkenfeld brings his science songwriting into the classroom through folk songs, raps, funny songs and even his popular YouTube music videos.
"You're kind of lying if you say you don't like live music," Burns said, "and whether you are doing great in his class or not, you can sit down and sort of enjoy the song and it kind of connects you to the material."
Classmate Sarah Weaver says this year's class is the reason she started to like science.
"You sort of just have to enjoy it when he's just so optimistic all the time," Weaver said, "and, I don't know, it's just such a good feeling he brings to the classroom."
Wolkenfeld says he's been using music to connect with students since his first teaching job, nearly three decades ago. But the work feels even more crucial now.
"Our federal government is really not on the side of justice and sustainability, and we need America to be on the right side of those issues," Wolkenfeld said. "So if I'm helping young people to figure out accurately how the world works, that is a really great thing and it makes me really happy."