The first of MIT’s six Climate Action Symposia, Progress in Climate Science, was held on Wednesday, October 2, 2019. Topics included: 1) the relationship between greenhouse gas concentrations in the atmosphere and global warming, extreme weather events, and other climate impacts; 2) remaining uncertainties and the prospects for reducing them; and 3) projected physical effects of increasing greenhouse gas emissions under alternative mitigation scenarios. The Climate Action Symposia series aims to advance our community’s understanding and expand our capacity to generate solutions for the urgent global challenge of climate change. Over the 2019-2020 academic year, the six symposia examine the current state of climate science and policy, as well as pathways for decarbonization of the global economy. We will also look at how universities can and should contribute solutions, including MIT’s efforts under our Plan for Action on Climate Change. In Part 1, Symposium Chair Kerry Emanuel introduces the event and MIT President Rafael Reif delivers welcoming remarks. Learn more about the MIT Climate Action Symposia: climate.mit.edu/symposia/ Learn more about the MIT Plan for Action on Climate Change: climate.mit.edu/climateaction/