Episode 6: Chris Bretherton

Chris Bretherton gravitated towards math and science as soon as he could read, which was at the tender age of three. His interest was probably the result of both genetics and family upbringing: Chris’ father is Francis Bretherton, a brilliant scientist who made important theoretical advances in fluid dynamics. This gave Chris big advantages, but he also talks about the shadow his dad cast over his career and the need he had to prove himself. “There are actually several other examples within our own field of father-son pairs who were relatively well-known. […] So it’s not actually that uncommon. And I suspect for all of the junior members of those partnerships, there’s always been the struggle of, on the one hand, wanting to be different, and on the other hand, being endowed both through genetics, and also through basically family acculturation and upbringing with all the skills to actually be good at the same field.” Because of his father’s work, Chris’ family moved from the UK to the US when he was eight years old. Chris’ fascination with math deepened over the years, but he also became interested in how to apply mathematical thinking to physical problems. He discovered the kind of physical problems that he would work on throughout his career when the family relocated to Boulder, Colorado, due to Francis Bretherton’s appointment as the director of the University Corporation for Atmospheric Research (UCAR). “It really took fire when I was a high school student in Colorado and I joined the Colorado Mountain Club. Because of being a rock climber and a mountaineer as a teenager, I was always very aware of the weather, very concerned about the weather, and experiencing it and its extreme settings, and so it then became rather natural to gravitate towards that later.” Chris has worked for his whole career on problems involving moist convection and clouds in the atmosphere, and the roles they play in the larger-scale weather and the climate. He made his name in the field for solving a major and fundamental problem involving shallow convection. In the 90s, using field observations and high-resolution models, Chris and his students figured out how the solid decks of low stratocumulus cloud over the cool subtropical oceans break up into much more scattered and taller cumulus clouds as the trade winds take them over warmer water. Since these low clouds were, and still are, poorly simulated in climate models, and yet they influence the global climate a lot because of the sunlight they reflect, understanding them is really important, and this work was a big breakthrough. Chris has made major advances on a wide range of other problems, including many aspects of deep convection in the tropics, and statistical methods. Recently, Chris left his long-held faculty position at the University of Washington to lead a climate modeling effort at Vulcan, the philanthropic organization of the late Microsoft co-founder Paul Allen. His team is using machine learning to make climate models better. It’s a big new direction for Chris and for climate science as a whole, and Adam and Chris get into that in the end of their conversation. The interview with Chris Bretherton was recorded in December 2021. Image credit: University of Washington College of the Environment Chris’ website at the University of Washington, and the website of the research team at the Allen Institute for AI, where Chris ist the Senior Director of Climate Modeling