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Latham J.,U.S. National Center for Atmospheric Research | Latham J.,University of Manchester | Bower K.,University of Manchester | Choularton T.,University of Manchester | And 22 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2012

The idea behind the marine cloud-brightening (MCB) geoengineering technique is that seeding marine stratocumulus clouds with copious quantities of roughly monodisperse sub-micrometre sea water particles might significantly enhance the cloud droplet number concentration, and thereby the cloud albedo and possibly longevity. This would produce a cooling, which general circulation model (GCM) computations suggest could-subject to satisfactory resolution of technical and scientific problems identified herein-have the capacity to balance global warming up to the carbon dioxide-doubling point. We describe herein an account of our recent research on a number of critical issues associated with MCB. This involves (i) GCM studies, which are our primary tools for evaluating globally the effectiveness of MCB, and assessing its climate impacts on rainfall amounts and distribution, and also polar sea-ice cover and thickness; (ii) high-resolution modelling of the effects of seeding on marine stratocumulus, which are required to understand the complex array of interacting processes involved in cloud brightening; (iii) microphysical modelling sensitivity studies, examining the influence of seeding amount, seedparticle salt-mass, air-mass characteristics, updraught speed and other parameters on cloud-albedo change; (iv) sea water spray-production techniques; (v) computational fluid dynamics studies of possible large-scale periodicities in Flettner rotors; and (vi) the planning of a three-stage limited-area field research experiment, with the primary objectives of technology testing and determining to what extent, if any, cloud albedo might be enhanced by seeding marine stratocumulus clouds on a spatial scale ofaround 100 × 100 km. We stress that there would be no justification for deployment of MCB unless it was clearly established that no significant adverse consequences would result. There would also need to be an international agreement firmly in favour of such action. © 2012 The Royal Society.

Neukermans A.,FICER | Cooper G.,FICER | Foster J.,FICER | Gadian A.,University of Leeds | And 4 more authors.
Atmospheric Research | Year: 2014

This paper is largely concerned with research focused on, but not restricted to, aspects of Marine Cloud Brightening (MCB), one of several geo-engineering ideas for reducing the amount of sunlight arriving at the Earth's surface, thereby compensating for global warming resulting from fossil-fuel burning. Predominant attention is given to the development of techniques for generating sprays of sub-micrometer salt particles that can enter marine stratocumulus clouds and increase their albedo, thus producing a cooling. Generation of sub-micrometer salt particles by spraying salt solutions at supercritical conditions is described, along with a description of the apparatus used. Log-normal particle size distributions having median diameters of 32 to 286. nm, with GSDs (Geometric Standard Deviations) around 2, were generated by two variations on the technique. © 2013 Elsevier B.V.

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