The “Green Sahara” era of humid climates in Africa might not seem, at first glance, to be part of CRANE’s purview. But CRANE post-doctoral researcher Deepak Chandan, who recently co-authored a research paper on climate modeling for that period with CRANE Co-Investigator, U of T Physics Professor W. Richard Peltier, says it’s very relevant to CRANE: “One of CRANE’s interests is to understand why settled habitation and civilizations arose in certain places,” he explains, and climate doesn’t stop at borders or oceans. “Climate in one part of the world can affect another. For example, research by U of T Physics graduate student Yiling Huo has shown that the West African monsoon has an impact as far away as Southeast Asia as well.”
One of the challenges of such Global Climate Models (CGMs), is that they are “very coarse”, as Chandan puts it, producing singular information for an area roughly 100 km by 100 km. Chandan and Peltier’s goal is to find out how climate affected different areas in different ways, and for that, they need to use “dynamical downscaling”, which involves running a higher-resolution Regional Coupled-Climate Model (RCM). Chandan says this model “gets hints for what the climate of the region should look like from the global model, but runs on a much higher-resolution grid, and contains physics that the coarser-resolution global model cannot simulate.” This model runs on a resolution of 30 km, and Chandan says they’re working to narrow it down even further, to 10 km.
Chandan also says that because there is so much data on the Green Sahara period, “you have a very good chance of finding relevant high-quality information that you can use to constrain the predictions of the models,” since the phenomenon that produced the Green Sahara affected other surrounding regions as well, including the Arabian Peninsula, Levant and Mesopotamia.
Chandan reports that U of T Physics graduate student Fengyi Xie has been working to perfect the modeling pipeline, which will facilitate the next step of the study involving agent-based modeling of Middle Eastern landscapes and land use, and the Bronze Age communities that lived in them. Chandan says that CRANE’s agent-based modeling effort integrates climate dynamics, simulated with a high-fidelity high-resolution model, and human dynamics. This not only helps to ground and refine climate models, it also “enables us to gain valuable insights into the adaptive strategies of these historical communities, as well as their longer-term environmental impacts.”
Written by Jaime Weinman (jaimeweinman.com).