Location
MC 5501
Speaker
Chris Fletcher, University of Waterloo
Title
Why does solar geoengineering become less effective as climate warming increases?
Abstract
Climate change caused by greenhouse gas emissions poses an existential threat to society and ecosystems over the coming century. Three decades of mitigation efforts have failed to move the trajectory of Earth’s climate warming below the UNFCCC’s 2-degree Paris target. Stop-gap measures like solar radiation geoengineering (SRM) aimed at offsetting the worst consequences of warming are, therefore, becoming increasingly attractive. However, aside from moral and environmental pollution risks, model simulations show that SRM is associated with deleterious climate impacts such as changes to critical global precipitation patterns. Evidence also suggests that over-engineering of SRM is required to offset an equivalent CO2 radiative forcing, but the physical explanation for this remains poorly understood. In this talk, I will present results from a series of novel simulations designed to study the efficacy of SRM and the physical causes of its declining efficiency under increasing CO2 emissions. The critical role of cloud feedbacks, combined with nonlinear interactions between SRM and CO2 forcing, are quantified. These results present clear evidence for why uncertainties in the response to SRM mean it may be imprudent to consider as an alternative to mitigation.