This is a shameless advert for new papers on the science and policy of solar radiation management.
The papers are available from the preprint section of my website (www.ucalgary.ca/~keith/Preprints.html<http://www.ucalgary.ca/~keith/Preprints.html>, earlier geoengineering papers and talks are at www.ucalgary.ca/~keith/geo.html<http://www.ucalgary.ca/~keith/geo.html>) Two papers are publishing in the next couple of weeks (The PNAS paper publishes Tuesday, it is embargoed until then, and the GRL paper is already on their website in preprint form, but it will be a few weeks before formal publication.) Jeffrey R. Pierce, Debra K. Weisenstein, Patricia Heckendorn, Thomas Peter and David W. Keith. Efficient formation of stratospheric aerosol for climate engineering by emission of condensable vapor from aircraft. Geophysical Research Letters. Copying volcanoes by injecting SO2 doesn't work very well because most of the added sulfur is deposited on the largest particles, producing the particle size distribution that is too large. Direct injection of sulfuric acid from an aircraft can allow much better control of particle size distribution. In our un-optimized models, it looks like this method can reduce the amount of sulfur needed to achieve 4 Wm-2 by more than a factor of two, and by a much larger factor when compared with injection of SO2 near the equator. Similar methods might be employed for other condensable vapors using technologies had been well explored in vapor phase fabrication of nano-scale particles. Note that: A preliminary look at the engineering suggest that these methods do not require any technological leap. Note also, that we have commissioned a study of delivery methods by aircraft engineering company and will release the entire report in the next month or so. David W. Keith. Photophoretic levitation of engineered aerosols for geoengineering. Proceedings of the National Academy of Sciences. 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. Oriented particles can be non-spherical allowing backscatter with essentially none of the forward scattering caused by small spherical aerosols. 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. Note: While cost and feasibility of producing and dispersing of such particles is unknown, analogies to existing particle fabrication technologies suggest that such methods cannot be dismissed out of hand. More generally, this suggest that there might be a range of technically sophisticated options beyond mimicking volcanoes that might offer advantages in the form of more controllable climate forcing, the downside is that it's far easier to think of new methods than it is to understand their effectiveness of environmental risks. The following two papers are under review at Climatic Change, but since their review process is long I want to make them available as preprints: Juan Moreno-Cruz, Katharine Ricke and David W. Keith, A simple model to account for regional inequalities in the effectiveness of solar radiation management. Submitted to Climatic Change. We calculate the amount of SRM that minimizes impacts using three different social objectives: egalitarian, utilitarian and ecocentric. While inequalities in the effectiveness of SRM between regions are important, they may not be as severe as is often assumed. When changes in precipitation and temperature are normalized by pre-industrial variability and weighted equally, we find that SRM could compensate for most of the damages caused by carbon-dioxide-driven climate change without making any region worse-off. While this method provides a parsimonious way to examine inequality, quantitative conclusions will require more realistic estimates of impact and of the climate's response to SRM. Put simply: This method helps describe inequalities, but we need to look at the effectiveness of SRM on actual impacts such as crop productivity, sea level rise, availability of surface water etc, rather than the stuff that's convenient for climate modelers such as annual average temperature and precipitation treated independently. Juan B Moreno-Cruz and David W Keith. Climate Policy under Uncertainty: A Case for Geoengineering. Climatic Change. We introduce SRM in a model of climate change economics and analyze the optimal policy under uncertainty. We find that the quick response allowed by SRM makes it important even if it is relatively ineffective at compensating for CO2-driven climate change or even if its costs are expected to be large compared to traditional mitigation strategies. Finally, we examine the implications of uncertainty about the effectiveness of SRM and show that the value of reducing this uncertainty can readily exceed several trillion US dollars over the next 100 years, providing a strong argument for a research program. David Keith Canada Research Chair in Energy and the Environment www.ucalgary.ca/~keith<http://www.ucalgary.ca/~keith> [email protected]<mailto:[email protected]> (403) 220-6154 -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
