Tracking Polluted Clouds: the Plausibility of a Strong Aerosol Cooling Effect on Earth’s Climate

forthcoming

Anthropogenic climate change is a tug-of-war with fossil fuels playing both sides of the field. Fossil fuel use emits both climate-warming greenhouse gases and climate-cooling aerosols. And aerosol impacts on clouds might have thus far masked a large fraction of greenhouse gas warming. If the aerosol cooling is strong, it implies 1) that the Earth’s climate is more sensitive to anthropogenic greenhouse gases than currently thought, and 2) reduced aerosol pollution has brought forward global warming. This project’s overarching hypothesis is that aerosol cooling is strong. I tackle this main hypothesis via the following specific hypotheses: - Thicker Clouds: Aerosols increase cloud thickness, challenging the current scientific understanding. - More Clouds: Cloud coverage and thickness consistently increase in response to aerosols due to suppressed precipitation. - Few Glaciated Clouds: The warming effect of anthropogenic aerosols glaciating supercooled clouds is weak compared to the cooling effects by thicker and more extensive clouds. To quantify poorly understood aerosol impacts on clouds, I will overlay remote sensing observations of clouds with anthropogenic air pollution hot spots in novel ways. Aerosols emitted by ships and industrial facilities induce polluted cloud tracks that serve as opportunistic experiments. By comparing the properties of polluted cloud tracks to those of nearby unpolluted clouds, I will infer the causal impact of aerosols on clouds. As the heart of the project, I will create an observatory to identify more than twelve million weak and strong cloud perturbations induced by aerosols from air pollution hot spots. A unique combination of weak and strong aerosol perturbations on clouds will allow me to quantify the least understood aerosol impacts on clouds and achieve unprecedented representativeness of cloud responses. I will scale cloud responses to aerosols to the global level to assess the plausibility of strong aerosol cooling.