I am Joel Thornton, Professor of Atmospheric Sciences at the University of Washington. My research focuses on microscopic nano-scale particles in the atmosphere, where they come from, and what they do to air quality, weather, and climate. These particles come in many shapes and sizes, from a variety of sources like wildfires, sea spray, desert dust, vegetation, and our own pollution from power plants, diesel trucks, cargo ships and so on. These particles can be toxic to human health, with the smallest more numerous ones getting into our lungs, but they are also good at reflecting sunlight to space, and they are the seeds on which every cloud droplet or snowflake forms so they have an out-sized influence on weather and climate. For example, my colleagues and I recently showed (http://onlinelibrary.wiley.com/doi/10.1002/2017GL074982/full) that lightning is twice as frequent above busy shipping lanes, likely because of the particles emitted in the ships exhaust! Ask me anything about atmospheric particles and how the nano-scale can effect the global scale. Ask me anything! I’ll be back at 12 pm Et to answer your questions, ask me anything! The AGU AMA series is conducted by the Sharing Science (sharingscience.org) program. Sharing Science: By scientists, for everyone. More at sharingscience.agu.org.