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UID:20250908T125519EDT-9574mPopUD@132.216.98.100
DTSTAMP:20250908T165519Z
DESCRIPTION:Please join us as we welcome Dr. John Dykema\, Project Scientis
 t from the John A. Paulson School of Engineering and Applied Sciences at H
 arvard University\, for a seminar titled 'Accurate assessment of large-sca
 le geoengineering impacts starts with accurate aerosol optical properties'
 . Coffee will be served.\n\nAbstract\n\nThe deliberate modification of the
  Earth’s albedo to partially offset the radiative forcing due to rising gr
 eenhouse gas concentrations is a type intervention that falls into the cat
 egory of geoengineering. The risks and feasibility of such an intervention
  achieved by increasing stratospheric sulphate aerosol optical depth is be
 ing studied using ensembles of climate models. These studies indicate that
  there are a number of physical side effects\, aside from sociopolitical r
 isks\, which are also serious. Sulphate aerosols significantly absorb infr
 ared radiation\, which heats the tropical tropopause layer\, increasing th
 e flux of water vapor into the stratosphere\, accelerating ozone loss\, an
 d increasing radiative forcing. Other side effects include perturbations t
 o the global hydrological cycle and increases in clear-sky diffuse radiati
 on. These side effects have motivated the investigation of alternatives\, 
 including solid aerosol materials. The high refractive index of some solid
  materials may lead to reduction in these risks associated with the radiat
 ive properties of aerosols intended to scatter solar radiation back to spa
 ce. A new analysis of the scattering efficiency and absorption of a range 
 of candidate solid aerosols will be presented. This analysis utilizes a co
 mprehensive radiative transfer model driven by updated\, physically consis
 tent estimates of optical properties. As part of the analysis\, the potent
 ial increase in stratospheric water vapor and associated longwave radiativ
 e forcing is computed. It is found that the stratospheric heating calculat
 ed in this analysis indicates some materials to be substantially riskier t
 han previous work. Another finding is that there are Earth-abundant materi
 als that may reduce some principal known risks relative to sulphate aeroso
 ls. An overview will be provided of laboratory experiments to improve the 
 understanding of the fundamental physical and chemical properties of solid
  aerosols suggested for albedo modification. The role of laboratory experi
 ments and process studies will be discussed as part of an overall strategy
  for improving the representation of these aerosols to improve accuracy of
  risk assessments\n
DTSTART:20160919T193000Z
DTEND:20160919T203000Z
LOCATION:Room 934\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:Seminar: Dr. John Dykema
URL:/meteo/channels/event/seminar-dr-john-dykema-26257
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