Bubble, bubble, toil and trouble

Seitz (2011) has proposed using micron-size bubbles in water to increase albedo and cool the water as an alternative to geoengineering in the stratosphere using sulfate aerosols. The slogan “Don’t dim the Sun; Brighten the water” appears twice in the paper. Seitz suggests that cooling oceanic regions this way would be a safer way to address the problem of global warming. The problem of global warming is real and potentially very dangerous (IPCC 2007). Society has various options for responding to this problem, nothing (the response so far), mitigation (reducing or eliminating emissions of greenhouse gases that are causing the warming—the far preferable option), adaptation and suffering in response to the warming and other climate impacts that are already happening and will grow in the future, and geoengineering. Geoengineering here will refer to “solar radiation management” attempts to reduce absorbed solar radiation to counteract the warming. Carbon capture and storage is also sometimes called geoengineering, but it has completely different ethical, risk, governance, and cost issues and will not be addressed here. Robock (2008a) and Robock et al. (2009) point out that while production of a stratospheric aerosol cloud would indeed cool the climate and prevent or reverse ice melting and sea level rise, it would also bring a large number of potential risks (Table 1). While Seitz correctly states that his bubble method would remove some of these risks, it would bring its own list of risks. These include impacts on convection in the ocean once you cool the ocean surface, which would remove the bubbles. A cooler ocean will also absorb CO2 more efficiently, enhancing ocean acidification. As artificial surfactants would be needed in some situations, the costs and environmental impacts of these chemicals may present problems. And what would be the effects of bubble clouds on oceanic life, through their effects on temperature and amount of sunlight? Bubble clouds would also induce changes in oceanic circulation and anom-