Oeste F. and Elsworth C. 2024 Tropospheric photosensitive Climate Catalyst Aerosols (CCAs) for climate cooling
Description
Since preindustrial times methane‘s atmospheric concentration has roughly tripled, so that it now contributes around 40% of the current energy imbalance causing global warming (Forster et al, 2023, Hansen et al, 2023). Methane has an instantaneous global warming potential per unit mass of 120x that of CO2, and globally there are millions of methane sources. However, it is not cost-effective to plug or otherwise remove all these sources, nor is it practical to capture methane from major sources such as wetlands or rice paddies. Methane currently has an average lifetime of around 9-10 years, and we propose shortening that by enhancing its natural sink using climate catalyst aerosols. As a highly inert volatile organic compound (VOC), methane is removed naturally from the air only by a process initiated by oxidative chemical radicals. These are mainly the hydroxyl radical (°OH), and the chlorine radical (°Cl). Depending on humidity, °Cl initiates methane oxidation at least 16x faster than °OH (Oeste et al, 2017). The atmosphere’s oxidative capacity (AOC) constituted by these radicals (i.e. methane sink) is increasingly consumed by VOC emissions and other sources such as carbon monoxide from wild-fires, agricultural slash and burn, and vehicle and industrial emissions. A future hydrogen economy will consume the AOC further, because H2 is a chemical reductant (i.e. reacts with oxidants). H2 is also a greenhouse gas with a global warming potential at least 8 times that of CO2 (Derwent 2023).