This presidential session will focus on the critical scientific challenge of separating anthropogenic signals from those associated with natural variability. Decades of work have delivered increasing clarity in this area and are enabling stronger science-based statements and more compelling advocacy. The Session will start with a keynote lecture by Ben Santer, this year's Rossby Medal winner. His keynote lecture will briefly summarize this scientific progress and the factors that enabled it. The end of the lecture will introduce the subject of event attribution, leading into a panel discussion of how climate scientists attempt to quantify the influence of human-caused climate change on the likelihood, physical properties, and impacts of extreme weather events.

