We have reached the 30 year mark of James Hansen’s landmark testimony to Congress about climate change. There’s been a lot of coverage about how strikingly accurate Hansen’s projections were. There have also been numerous interviews with him that focus on his regrets about not being more effective at communicating the danger climate change poses.

Over the years, Hansen maintained a busy speaking schedule even as he continued to conduct research full-time. I met him about a decade ago at a scientific conference. He spoke to a room of fewer than 100 people, and stayed after his speech for as long as there were people who wanted to talk with him. If he had any failings in communicating about climate science, they didn’t have to do with effort or commitment.

Hansen also played an important role in showing climate scientists that they can be activists without jeopardizing their research, and that they had a moral obligation to speak out. Grist has a Q&A with 10 climate scientists about what Hansen means to them. Hansen is a towering figure in the field, and it’s nice to see people reflect on the particulars of his influence.