A year that started with the mass introduction of Covid vaccines and the astonishing scenes of rioting at the Capitol is ending with concern about new virus variants and fears about the effects of a warming climate.As we approach the end of the year, we listen back to more of the events that defined 2021.Sign up here to get The Daily in your inbox each morning. And for an exclusive look at how the biggest stories on our show come together, subscribe to our newsletter. Background reading: In a volatile year again dominated by politics and the pandemic, “The Daily” sought out personal stories. Here’s a look back on the episodes that our team can’t forget.For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.