4 December 2018 from 09:30 to 17:30

Symposium: (Sulphate) Geoengineering - Feasibility, Risks, Alternatives

We know from volcanic eruptions that sulphate aerosol in the stratosphere can temporally cool the climate. Can we use this effect artificially to solve the global warming problem?

Humanity has not yet succeeded in reducing CO2 emissions significantly. Can we artificially cool te planet by mimicking volcanic eruptions? 

Prof. Alan Robock (Rutgers University, US) will visit CCSS to discuss the effect of aerosol on climate. On December 4rd, we will organise a symposium on geoengineering: Can we hack our way out of climate change, or would the cure be worse than the disease? What are the benefits, dangers, and alternatives? 


  • from 09:30     arrival 
  • 9:50-10:00 Claudia Wieners and Henk Dijkstra - Opening
  • 10:00-10:40 Stephan de Roode - Cloud microphysics aspects of Marine Cloud Brightening
  • 10:40-11:20 Steve Hulshoff  - Technical and Financial Feasibility of Geoengineering using Aircraft
  • 11:20-11:30 coffee break  
  • 11:30-12:30: Alan Robock - Stratospheric Sulfur Geoengineering - Benefits and Risks (see abstract below)
  • 12:30-13:30 lunch break
  • 13:30-14:10: Claudia Wieners - Economic Cost-Benefit Analysis of Geoengineering using Nordhaus’ DICE model
  • 14:10-14:50: Aravind Purushothaman Vellayani - Bioenergy and Negative Emissions
  • 14:50-15:30: Detlef van Vuuren: Economic Aspects of Negative Emissions
  • 15:30-16:00: cake and coffee 
  • 16:00-16:40: Andrew Lockley - Security of Solar Radiation Management geoengineering
  • afterwards: discussion - (Sulphate) Geoengineering: A Cool Plan or Megalomania? 

The symposium is open to all interested researchers, but please register with the form below. 


Keynote Speaker: Alan Robock

Alan Robock is Distinguished Professor at the department of environmental sciences at Rutgers University (US) since 1998. Previously, he worked at the Department of Meteorology at the University Maryland (1977-1997) and was State Climatologist of Maryland (1991-1997). His research involves many aspects of climate change, using both observational analyses and climate model simulations. Currently, he focuses on geoengineering, climatic effects of nuclear weapons, and the effects of volcanic eruptions on climate. Alan Robock has published more than 240 peer-reviewed papers and received numerous awards, including the Jule G. Charney Medal of the American Meteorological Society, 2015. He was participant in the International Campaign to Abolish Nuclear Weapons, which was awarded the Nobel Peace Prize in 2017.

Keynote talk: Stratospheric Sulfur Geoengineering – Benefits and Risks

Geoengineering, also called climate engineering, has been proposed as a “solution” to global warming, involving “solar radiation management (SRM)” by injecting particles into the stratosphere, brightening clouds, or blocking sunlight with satellites between the Sun and Earth.  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 and regional hydrologic responses.  No such systems to conduct stratospheric geoengineering now exist, but a comparison of different proposed stratospheric injection schemes, using airplanes, balloons, and artillery, shows that using airplanes to put sulfur gases into the stratosphere would not be expensive.  Nevertheless, it would be very difficult to create stratospheric sulfate particles with a desirable size distribution.

            Our Geoengineering Model Intercomparison Project (GeoMIP), conducting climate model experiments with standard stratospheric aerosol injection scenarios, is ongoing.  We have found that if we could counteract increasing greenhouse gases with insolation reduction we could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world.  Temperature extremes would still increase, but not as much as without SRM.  If SRM were halted all at once, there would be rapid temperature and precipitation increases at 5-10 times the rates from gradual global warming.  This would have devastating impacts on natural ecosystems.  SRM combined with CO2 fertilization would have small impacts on rice production in China, but would increase maize production.  SRM using stratospheric aerosols would reduce stratospheric ozone and enhance surface UV-B radiation.  The enhanced downward diffuse radiation would increase the surface CO2 sink. 

            If there were a way to continuously inject SO2 into the lower stratosphere, it would produce global cooling, stopping melting of the ice caps, and increasing the uptake of CO2 by plants.  But there are at least 27 reasons why stratospheric geoengineering may be a bad idea.  These include disruption of the Asian 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, there are concerns about commercial or military control, and it may seriously degrade terrestrial astronomy and satellite remote sensing.  Global efforts to reduce anthropogenic emissions (mitigation) and to adapt to climate change are a much better way to channel our resources to address anthropogenic global warming.


Location: Centre for Complex Systems Studies, room 4.16, Minnaert Building, Leuvenlaan 4, De Uithof, Utrecht

For other events during Alan's visit, see here

If you have any questions, please contact the CLUe coordinator Claudia Wieners (c.e.wieners@uu.nl)

Start date and time
4 December 2018 09:30
End date and time
4 December 2018 17:30