Continuing our centennial series "100 Years of 100 Things," Michael E. Mann, presidential distinguished professor and director of the Center for Science, Sustainability and the Media at the University of Pennsylvania and author of several books, most recently,Our Fragile Moment: How Lessons from Earth's Past Can Help Us Survive the Climate Crisis (PublicAffairs, 2023), walks us through the impact that fossil fuels have had on the climate—and the temperature record—of the past 100 years.