Last week, 98-year-old David Perlman will retire from the San Francisco Chronicle, nearly 60 years after he started filing science stories for the paper on a portable typewriter. Perlman covered the start of World War II, the height of the AIDS epidemic and traveled as far as Antarctica and Ethiopia for work. He joins us to talk about his career, his thoughts on climate change and what he'll do now that he's left the newsroom that affectionately calls him "Dr. Dave."