Special Seminar: Henri Drake

Title: Climate Mitigation Modeling: Past, Present, and Future

Abstract: Global climate models pioneered at NOAA’s Geophysical Fluid Dynamics Laboratory in the 1960s and now frequently run on the world’s largest supercomputers, have become a foundational tool for understanding the Earth system and its response to external forcing. Based on plausible scenarios of radiatively-active pollution and land-use changes, model projections of the future have highlighted the benefits of mitigation policies and guided international policy negotiations. Since the emergence of forced climate signals occurs on timescales much longer than climate model development cycles (unlike, say, weather forecast models that try to predict the next day’s rainfall), confidence in the future projections generated by climate models instead relies on their historical accuracy, robustness, and support by background knowledge.

In the first part of the talk, I will complement these conventional tests of climate models by applying a brute-force forecast-verification test to the earliest generations of numerical climate models. I will show that the key climate model projections of transient global warming, land-sea warming contrast, Arctic amplification, and arctic sea ice melt have largely come to pass. This qualitative agreement is particularly encouraging given that model bias has decreased nearly monotonically with every new generation of climate models.

In the second part of the talk, I will reflect on the tragic irony that we only know that our climate models are accurate because we waited long enough for the changes they warned about to actually materialize. I will review the current state of mitigation efforts and present a political scientific argument that suggests a coalition of youth-led and science-based social movements could yet bring about emissions mitigation consistent with global climate goals. I will illustrate this optimistic scenario by introducing a stabilizing human-climate feedback within a climate-economic model that weighs the costs of mitigation against the benefits of avoiding climate damages.