Smoke from wildfires in Canada has created a crisis in the American Northeast and beyond, with air pollution in New York reaching its worst level in modern history.David Wallace-Wells, a climate columnist for The Times, explains why this happened, and why there is so little we can do to keep it from happening again.Guest: David Wallace-Wells, a climate columnist correspondent for The New York Times.Background reading: New York City experienced its worst air quality on record. Here’s how to stay safe as the smoke spreads.David Wallace-Well’s column on the smoke that shrouded New York City.For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.