title: Photophoretic levitation of engineered aerosols for geoengineering.
abstract: Aerosols could be injected into the upper atmosphere to engineer the climate by scattering incident sunlight so as to produce a cooling tendency that may mitigate the risks posed by the accumulation of greenhouse gases. Analysis of climate engineering has focused on sulfate aerosols. Here I examine the possibility that engineered nanoparticles could exploit photophoretic forces, enabling more control over particle distribution and lifetime than is possible with sulfates, perhaps allowing climate engineering to be accomplished with fewer side effects. The use of electrostatic or magnetic materials enables a class of photophoretic forces not found in nature. Photophoretic levitation could loft particles above the stratosphere, reducing their capacity to interfere with ozone chemistry; and, by increasing particle lifetimes, it would reduce the need for continual replenishment of the aerosol. Moreover, particles might be engineered to drift poleward enabling albedo modification to be tailored to counter polar warming while minimizing the impact on equatorial climates.
authors.affiliation: Energy and Environmental Systems Group, University of Calgary, 2500 University Drive NW, Calgary AB, Canada T2N 1N4. keith@ucalgary.ca
authors.forename: David W
authors.initials: DW
authors.lastname: Keith
references.citation: Science. 2006 Oct 20;314(5798):452-4
references.pmid: 16973840
references.citation: Proc Natl Acad Sci U S A. 2006 Nov 14;103(46):17184-9
references.pmid: 17085589
references.citation: Science. 2004 Jun 11;304(5677):1650-3
references.pmid: 15192223
references.citation: Environ Sci Technol. 2009 Apr 15;43(8):2784-6
references.pmid: 19475950
references.citation: Science. 2002 Apr 26;296(5568):727-30
references.pmid: 11976452
references.citation: Science. 2003 Mar 28;299(5615):2035-8
references.pmid: 12663919
references.citation: Proc Natl Acad Sci U S A. 2007 Nov 20;104(47):18866-70
references.pmid: 17962418
references.citation: Science. 2008 May 30;320(5880):1201-4
references.pmid: 18436741
references.citation: Nature. 2010 Jan 28;463(7280):426-7
references.pmid: 20110972