14.01.2026 - Seminars
Past Perfect, Future Imperfect? Biases in Reduced Complexity Climate Models tuned to the historical record
Dargan Frierson, Associate Professor Dept. of Atmospheric Sciences University of Washington
14/01/2026 ore 11:00
CNR-ISAC, Bologna meeting room and online
Abstract
Some of the most important decisions about the future regarding climate and energy policy are decided on the basis of results from reduced complexity climate models (RCMs), which take emissions of pollutants and calculate global average temperature. RCMs are tuned from comprehensive Earth Systems Models (ESMs), but use very simple equations. They’ve also received relatively little scrutiny in the scientific literature. We study one particular RCM called “fair,” which was used in recent IPCC reports to estimate the remaining carbon budget to keep warming under 1.5 or 2 C. Although fair is constrained to essentially exactly reproduce current CO2 concentrations, we show that it underestimates future CO2 concentrations significantly compared with the models to which it is tuned. We provide an explanation and discuss implications for RCM development, including ESM scenarios that would be useful for ensuring that RCMs are accurate.
Bio
Dargan Frierson is Associate Professor Dept. of Atmospheric Sciences University of Washington
His research focuses on climate and climate change, with a particular emphasis on simplified models designed to improve our understanding of climate processes. He study the effects of water vapor, clouds, and dynamical processes on the Earth’s climate, while integrating a justice-based perspective into climate action.