Nick Lutsko, from Scripps Institution of Oceanography, will present a talk at the SEAS Colloquium in Climate Science (SCiCS).

Title: The Physics of Extreme Heat Events

Abstract: Changes in temperature extremes are potentially one of the most severe impacts of climate change, with many negative consequences for human societies and natural ecosystems. In this talk, I will present recent work investigating the factors governing heat stress and temperature extremes, and how these change in a warmer world. First, I will derive conditions on present-day climate for whether moisture or temperature dominates local changes in heat stress. These conditions will be used to guide an analysis of CMIP6 data, which suggests that the response of heat stress to CO2 forcings is largely determined by the response of specific humidity, with temperature changes playing a secondary role. Thus, understanding regional changes in specific humidity is largely sufficient for understanding regional changes in heat stress. Implications of this work for public health and physiology studies will also be discussed. In the second part of the talk I will present radiative constraints on Earth's warmest surface temperatures: the warmest temperatures ever recorded are roughly 55C, but why not 65$^\circ$C, or 45$^\circ$C? Simple energy balance models in combination with line-by-line radiation calculations will be used to explain this value, and to predict how it will change in a warmer world. This allows us to constrain just how hot heat waves can get on Earth.

Bio: Nick Lutsko is an Assistant Professor of Climate Science at the Scripps Institution of Oceanography. He did his undergraduate degree in geophysics at Imperial College London, graduating in 2012. He then did a PhD at Princeton under Isaac Held, where he defended his thesis in 2017. He did a 2 year postdoc at MIT with Tim Cronin, and started at Scripps in January 2020. His research interests are in large-scale climate dynamics, especially focused on the atmosphere, climate sensitivity and radiation.