Sea-going hardware for the cloud albedo method of reversing global warming

Abstract

Following the review by Latham et al. (Latham et al. 2008 Phil. Trans. R. Soc. A 366) of a strategy to reduce insolation by exploiting the Twomey effect, the present paper describes in outline the rationale and underlying engineering hardware that may bring the strategy from concept to operation. Wind-driven spray vessels will sail back and forth perpendicular to the local prevailing wind and release micron-sized drops of seawater into the turbulent boundary layer beneath marine stratocumulus clouds. The combination of wind and vessel movements will treat a large area of sky. When residues left after drop evaporation reach cloud level they will provide many new cloud condensation nuclei giving more but smaller drops and so will increase the cloud albedo to reflect solar energy back out to space. If the possible power increase of 3.7 W m K2 from double pre-industrial CO 2 is divided by the 24-hour solar input of 340 W m K2 , a global albedo increase of only 1.1 per cent will produce a sufficient offset. The method is not intended to make new clouds. It will just make existing clouds whiter. This paper describes the design of 300 tonne ships powered by Flettner rotors rather than conventional sails. The vessels will drag turbines resembling oversized propellers through the water to provide the means for generating electrical energy. Some will be used for rotor spin, but most will be used to create spray by pumping 30 kg s K1 of carefully filtered water through banks of filters and then to micro-nozzles with piezoelectric excitation to vary drop diameter. The rotors offer a convenient housing for spray nozzles with fan assistance to help initial dispersion. The ratio of solar energy reflected by a drop at the top of a cloud to the energy needed to make the surface area of the nucleus on which it has grown is many orders of magnitude and so the spray quantities needed to achieve sufficient global cooling are technically feasible.

A comparison of the climate impacts of geoengineering by stratospheric SO2 injection and by brightening of marine stratocumulus cloud

“…For SO 2 injection, the distribution of cooling is similar to the GHG-induced warming, and the changes in land precipitation, while small, generally tend to oppose those induced by GHGs. In contrast, the temperature and precipitation changes caused by stratocumulus modification are quite different, and in the case of South America, act to enhance, not reduce, both ( Salter et al, 2008). Not only are the cloud's radiative properties and lifetime sensitive to perturbation by geoengineering, but the lifetime of sea-salt in the atmosphere subsequent to injection is longer than elsewhere owing to reduced precipitation.…”

An Analysis of the Optimal Mix of Global Energy Resources and the Potential Need for Geoengineering Using the CEAGOM Model

“…The amount of sea spray and sulfur injection geoengineering deployed was significant; however, it was still well within the realm of what is theoretically feasible (see refs. [8] and [10]). Also of note is that the optimal solution still called for significant amounts of geoengineering even when a substantial penalty was applied as shown by the results for the GeoPen-CL and GeoPen2-CL cases.…”

“…The cost of deploying 25 m 3 s −1 of sea spray injection is only $2.6 billion based on cost estimates in ref. [10]. Similarly, the cost of deploying 2.5 million metric tons of sulfur injection as described in the GeoPen2-CL case would involve a capital cost for the needed aircraft of roughly $2.63 billion and an annual cost for the deployment of $1.14 billion using the data from ref.…”

“…Does not reduce the actual atmospheric greenhouse gas concentration, so must be constantly deployed Sea spray injection [9,10] Injection of sea water droplets into the air to thicken low-level maritime clouds, thereby increasing albedo…”

Bright water: hydrosols, water conservation and climate change

“…To determine the priority appropriate for study and potential deployment of hydrosols, a comparison is needed of advantages and disadvantages with respect to other approaches, such as stratospheric aerosol deployment (Crutzen 2006;Rasch et al 2008), augmentation of cloud cover (Latham 1990(Latham , 2002Salter 2008), and direct steps to reduce or reverse increases in the CO 2 concentration (Keith et al 2005). …”