Department Seminar: Julie Edwards

Title: Climate change detection and attribution using tree rings

Abstract: Understanding the drivers of climate change, and distinguishing human influence from natural variability, is essential for decision-making, policy, and environmental management. To understand how and why the climate is changing, we must distinguish externally forced trends from the backdrop of internal climate variability. This talk presents how tree-ring paleoclimate data can improve our ability to detect and attribute climate change, particularly when short observational records and high natural variability increase uncertainty in future projections. Using three case studies, I show how using both tree-ring records and climate general circulation models can improve our understanding of climate change detection and attribution. In high-latitude northwest North America, high-resolution cellular-scale measurements of tree-ring data improve proxy-model agreement for long-term temperature variability, reducing the risk of false positives in attributing trends to anthropogenic forcing. I also demonstrate how internal variability, along with the biological nature of tree-ring data, can complicate the interpretation of post-volcanic eruption cooling in the paleoclimate record. Finally, I will introduce recent work using sub-seasonal tree-ring data to reconstruct extreme precipitation and atmospheric river activity in Southern California. These reconstructions will be compared to multi-model large ensembles to evaluate how well climate models represent the frequency and variability of extreme precipitation events. Together, these examples highlight how high-resolution tree-ring data can help resolve proxy–model discrepancies, strengthening our ability to disentangle the effects of external forcing on the climate system.