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SUMMARY:Stratospheric Sulfur Geoengineering – Benefits and Risks - Profe
 ssor Alan Robock\, Department of Environmental Sciences\, Rutgers Universi
 ty
DTSTART:20160321T113000Z
DTEND:20160321T124500Z
UID:TALK65022@talks.cam.ac.uk
CONTACT:Paul Griffiths
DESCRIPTION:Geoengineering\, also called climate engineering\, has been pr
 oposed as a “solution” to global warming\, involving “solar radiatio
 n management (SRM)” by injecting particles into the stratosphere\, brigh
 tening clouds\, or blocking sunlight with satellites between the Sun and E
 arth.  While volcanic eruptions have been suggested as innocuous examples 
 of stratospheric aerosols cooling the planet\, the volcano analog actually
  argues against stratospheric geoengineering because of ozone depletion an
 d regional hydrologic responses.  No such systems to conduct stratospheric
  geoengineering now exist\, but a comparison of different proposed stratos
 pheric injection schemes\, using airplanes\, balloons\, and artillery\, sh
 ows that using airplanes to put sulfur gases into the stratosphere would n
 ot be expensive.  Nevertheless\, it would be very difficult to create stra
 tospheric sulfate particles with a desirable size distribution.\n\nOur Geo
 engineering Model Intercomparison Project (GeoMIP)\, conducting climate mo
 del experiments with standard stratospheric aerosol injection scenarios\, 
 is ongoing.  We have found that if we could counteract increasing greenhou
 se gases with insolation reduction we could keep the global average temper
 ature constant\, but global average precipitation would reduce\, particula
 rly in summer monsoon regions around the world.  Temperature changes would
  also not be uniform.  The tropics would cool\, but high latitudes would w
 arm\, with continuing\, but reduced sea ice and ice sheet melting.  Temper
 ature extremes would still increase\, but not as much as without SRM.  If 
 SRM were halted all at once\, there would be rapid temperature and precipi
 tation increases at 5-10 times the rates from gradual global warming.  SRM
  combined with CO2 fertilization would have small impacts on rice producti
 on in China\, but would increase maize production.  SRM using stratospheri
 c aerosols would reduce stratospheric ozone and enhance surface UV-B radia
 tion.  The enhanced downward diffuse radiation would increase the surface 
 CO2 sink.  We are currently investigating the various mechanisms involved 
 in impacts on the land biosphere with climate models.\n\nIf there were a w
 ay to continuously inject SO2 into the lower stratosphere\, it would produ
 ce global cooling\, stopping melting of the ice caps\, and increasing the 
 uptake of CO2 by plants.  But there are at least 27 reasons why stratosphe
 ric geoengineering may be a bad idea.  These include disruption of the Asi
 an and African summer monsoons\, reducing precipitation to the food supply
  for billions of people\; ozone depletion\; no more blue skies\; reduction
  of solar power\; and rapid global warming if it stops.  Furthermore\, the
 re are concerns about commercial or military control\, and it may seriousl
 y degrade terrestrial astronomy and satellite remote sensing.  Global effo
 rts to reduce anthropogenic emissions (mitigation) and to adapt to climate
  change are a much better way to channel our resources to address anthropo
 genic global warming.\n
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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