Known Unknowns of Regional Hydroclimate Change Projections

March 26, 2026

Flavio Lehner

Hosted by Maria Rugenstein

Abstract

While warming targets and carbon mitigation policies are often discussed at global levels, climate change impacts and adaptation unfold at local to regional scales. When zooming into those scales, uncertainties in climate change projections grow and can complicate decision making. Here, we source these uncertainties and provide examples of how they play out in a few case studies focused on the hydrological cycle. We revisit the attribution of the recent sustained drought in the Southwestern U.S. in light of model-observation discrepancies in Pacific sea surface temperatures, discuss the potential to reduce uncertainties in runoff projections by focusing on model biases in sensitivity rather than mean state, and explore the effect of model resolution on the depiction of snowpack resilience over the Western U.S.

Flavio Lehner obtained a PhD in Climate Science from the University of Bern in Switzerland in 2013. After a brief engagement as Science Officer in the Technical Support Unit for the IPCC Fifth Assessment Report, he joined the Climate and Global Dynamics Lab at NCAR with a postdoc fellowship from the Swiss National Science Foundation in 2014. Being awarded a NOAA postdoc fellowship, he continued on in NCAR’s Research Applications Lab. He then transitioned to a Project Scientist position at NCAR, leading and co-leading projects across NCAR labs. After a “sabbatical year” as a Senior Scientist at ETH Zürich in Switzerland, he joined Cornell as an Assistant Professor in 2020. He also acts as the Chief Climate Scientist for the conservation non-profit Polar Bears International.