Becky Alexander is an atmospheric scientist who studies the feedbacks that arise between climate change and the chemical composition of the atmosphere. She is currently the director of the Program on Climate Change. She looks at the pathways by which atmospheric pollutants form, how those pathways can vary across time and space, and what that means both for present-day air quality and for the future of climate change. To tackle her questions, she does extensive lab work with polar ice cores and atmospheric aerosols, using them to understand how the atmosphere has responded to climate change over the past 100,000 years. She also builds three-dimensional models to see how atmospheric chemistry has responded to climate change over the last 100,000 years.