Role of Cloud Feedback in Continental Warming Response to CO2 Physiological Forcing

Stomatal closure is a major physiological response to the increasing atmospheric carbon dioxide (CO2), which can lead to surface warming by regulating surface energy fluxes-a phenomenon known as CO2 physiological forcing. The magnitude of land surface warming caused by physiological forcing is substantial and varies across models. Here we assess the continental warming response to CO2 physiological forcing and quantify the resultant climate feedback using carbon-climate simulations from phases 5 and 6 of the Coupled Model Intercomparison Project, with a focus on identifying the cause of intermodel spread. It is demonstrated that the continental (40 degrees-70 degrees N) warming response to the physiological forcing in summer (similar to 0.55 K) is amplified primarily due to cloud feedback (similar to 1.05 K), whereas the other climate feedbacks, ranging from -0.57 to 0.20 K, show relatively minor contributions. In addition, the strength of cloud feedback varies considerably across models, which plays a primary role in leading large diversity of the continental warming response to the physiological forcing.