Report from Royal Society (2009)


Geoengineering the climate: science, governance and uncertainty



6 Conclusions and recommendations

  • The assessments are preliminary because of lack of research. General assessment is still valid.


  • Geoengineering is likely to be
    • tech feasible
    • could substantially reduce costs of climate change
    • could substantially reduce risk of climate change
  • Major uncertainties
  • Not mid term
  • Should not divert from emissions reduction

  • We are failing in reductions today = we might need geoengineering as a complement

  • We need
    • International coordination of research on the most promising methods
    • International cooperation to assess feasibility, risks, benefits ... and governance
    • Public dialog and aligned governance on research, development, deployement

This is the start : We are failing today to stay below 2C ... This is from 2009! What has changed since then?


  • We should compare how good each method is at reducing temperature ... not easy since the Techs are very different
  • CDR vs SRM:
    • Timescale
    • effect on non temperature impacts of climate change
    • risk levels



  • No tech can substitute for reducing emissions
  • No clear winner today + depends on what we want to achieve
  • CDR
    • Lower risk
    • Addresses the source (not just temperature)
    • Longer time scale
    • Impact on local environments / trade offs
    • CDR methods are classified in order of potential
  • SRM
    • Termination problem: it needs to be maintained over centuries
    • Do not address ocean acidification
    • Introduces local variations in precipitations, wind, biodiversity ... / not a copy of our current climate
    • Might work in case of emergency
    • SRM methods are classified in order of potential
      • Stratospheric aerosol methods
        • most potential: large scale impact thanks to uniform distribution of effect
        • High risk
      • Cloud brightening methods
        • Localized temperature reduction
        • Easier to test and less governance problems
      • Space based
        • More uniform
        • Might work best if long term is needed
        • Not feasible today
        • Exit strategy might be easier


    • Need to assess these technologies and costs based on best available science
      • Legality
      • Effectiveness
      • Timeliness of implementation and effect
      • Eviro, social and economic impacts + unintended consequences
      • Costs (direct and indirect)
      • Funding
      • Public acceptability
      • Reversibility


    • This will have a critical impact on develop of these methods
    • Need to work on
      • Transparency
      • independence of commercial interests in evaluating the options
      • proper evaluation of impacts
    • Public attitude dominated by risks of things going wrong
      • Generally negative
      • depend on the method


    • Governance issues are substantial and serious
      • There will be winners and losers
    • Today: no treaties or institutions can regulate the range of activities ... fear that a lone state / company / individual could do geoengineering on his own
    • 6.7

    • Research is urgently needed to evaluate feasibility and risks
      • Small scale field experiements
      • Modelling
      • Enviro and social impact
      • Costs
      • Removing other gases than CO2?
    • Progress can be made cheaply: a few % of R&D of new energy development